ILLINOIS POWER CO
S-3, 1999-01-22
ELECTRIC & OTHER SERVICES COMBINED
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<PAGE>   1
 
    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JANUARY 22, 1999
 
                                           REGISTRATION STATEMENT NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                             ---------------------
                                    FORM S-3
            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
                             ---------------------
                             ILLINOIS POWER COMPANY
             (Exact name of Registrant as specified in its charter)
                             ---------------------
 
<TABLE>
<S>                                            <C>
              STATE OF ILLINOIS                                  37-0344645
       (State or other jurisdiction of                        (I.R.S. Employer
        incorporation or organization)                      Identification No.)
</TABLE>
 
                             500 SOUTH 27TH STREET
                            DECATUR, ILLINOIS 62525
                                 (217) 424-6600
         (Address, including zip code, and telephone number, including
            area code, of Registrant's principal executive offices)
 
                         CHARLES E. BAYLESS, CHAIRMAN,
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                             500 SOUTH 27TH STREET
                            DECATUR, ILLINOIS 62525
                                 (217) 424-7152
           (Name, address, including zip code, and telephone number,
                   including area code, of agent for service)
 
                                    Copy to:
 
                             ROBERT J. REGAN, ESQ.
                             SCHIFF HARDIN & WAITE
                                6600 SEARS TOWER
                            CHICAGO, ILLINOIS 60606
                                 (312) 258-5606
                             ---------------------
     APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: From time
to time after the effective date of this Registration Statement.
                             ---------------------
     If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box.  [ ]
     If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, as amended, other than securities offered only in connection with dividend
or interest reinvestment plans, check the following box.  [X]
     If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering.  [ ]
     If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ]
     If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box.  [ ]
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------------
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                                                  PROPOSED MAXIMUM        PROPOSED MAXIMUM
 TITLE OF SECURITIES        AMOUNT TO BE           OFFERING PRICE            AGGREGATE               AMOUNT OF
  TO BE REGISTERED           REGISTERED             PER UNIT(1)          OFFERING PRICE(1)        REGISTRATION FEE
- ---------------------------------------------------------------------------------------------------------------------
<S>                    <C>                     <C>                     <C>                     <C>
Debt Securities......       $250,000,000                100%                $250,000,000              $69,500
- ---------------------------------------------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------------------------------------------
</TABLE>
 
(1) Estimated solely for the purpose of calculating the registration fee.
 
     THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933, OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   2
 
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. WE MAY
NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER
TO SELL THESE SECURITIES AND WE ARE NOT SOLICITING OFFERS TO BUY THESE
SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.
 
PROSPECTUS                                SUBJECT TO COMPLETION JANUARY 22, 1999
 
                                  $250,000,000
 
                             ILLINOIS POWER COMPANY
 
                                DEBT SECURITIES
                           -------------------------
 
     We intend from time to time to offer, in one or more series, up to
$250,000,000 aggregate principal amount of our New Mortgage Bonds or other debt
securities (collectively, "Securities").
 
     We will provide the specific terms of the series of Securities in one or
more supplements to this Prospectus. You should read this Prospectus and any
Prospectus Supplement carefully before you invest in the Securities.
                           -------------------------
 
NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.
                           -------------------------
 
     We may offer the Securities in any of the following ways:
 
          - directly to you,
 
          - through dealers,
 
          - through underwriters,
 
          - through agents, or
 
          - through any combination of these methods.
 
     You can find additional information about our plan of distribution for
Securities under the heading "Plan of Distribution," which appears later in this
Prospectus. We will also describe the plan of distribution for any particular
series of Securities in the Prospectus Supplement for that series.
                           -------------------------
 
             THE DATE OF THIS PROSPECTUS IS                , 1999.
<PAGE>   3
 
     YOU SHOULD RELY ONLY ON THE INFORMATION PROVIDED IN OR INCORPORATED BY
REFERENCE IN THIS PROSPECTUS AND ANY PROSPECTUS SUPPLEMENT. WE HAVE NOT
AUTHORIZED ANYONE TO PROVIDE YOU WITH DIFFERENT INFORMATION. THE INFORMATION
CONTAINED IN THIS PROSPECTUS AND ANY PROSPECTUS SUPPLEMENT IS CURRENT ONLY AS OF
THE DATE OF SUCH PROSPECTUS OR PROSPECTUS SUPPLEMENT. WE ARE NOT MAKING AN OFFER
TO SELL OR SOLICITING AN OFFER TO BUY THE SECURITIES IN ANY JURISDICTION TO ANY
PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH OFFER OR SOLICITATION IN SUCH
JURISDICTION.
 
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                               PAGE
                                                               ----
<S>                                                            <C>
Where You Can Find More Information.........................     3
Documents Incorporated by Reference.........................     3
Forward-Looking Statements..................................     4
The Company.................................................     4
Use of Proceeds.............................................     4
Ratio of Earnings to Fixed Charges..........................     5
Description of the New Mortgage Bonds.......................     5
Description of the Unsecured Debt Securities................    20
Plan of Distribution........................................    23
Legal Opinions..............................................    23
Experts.....................................................    24
</TABLE>
 
                                        2
<PAGE>   4
 
                      WHERE YOU CAN FIND MORE INFORMATION
 
     We have filed with the Securities and Exchange Commission (the
"Commission") in Washington, D.C., a Registration Statement on Form S-3
(together with its amendments and exhibits, the "Registration Statement"), under
the Securities Act of 1933, as amended (the "Securities Act"), with respect to
the securities offered in this Prospectus. We have not included certain portions
of the Registration Statement in this Prospectus as permitted by the
Commission's rules and regulations. For further information, you should refer to
the Registration Statement.
 
     We are subject to the informational requirements of the Securities Act of
1934, as amended (the "Exchange Act"), and therefore we file annual, quarterly
and current reports, proxy and information statements and other information with
the Commission. You may inspect and copy the Registration Statement, as well as
the reports and other information filed by the Company with the Commission, at
the Commission's public reference facilities at its principal offices at
Judiciary Plaza, 450 Fifth Street, N.W., Room 1024, Washington, D.C. 20549 and
its regional offices at Northwest Atrium Center, 500 West Madison Street, Suite
1400, Chicago, Illinois 60661 and Seven World Trade Center, 13th Floor, New
York, New York 10048. You may obtain information on the operation of the
Commission's public reference facilities by calling 1-800-SEC-0330. You may also
obtain information filed by us at the Commission's Web site on the World Wide
Web at http://www.sec.gov. You may obtain these materials at set rates from the
Public Reference Section of the Commission at its principal office at Judiciary
Plaza, 450 Fifth Street, N.W., Washington, D.C. 20549. Finally, you may inspect
our filings at the offices of the New York Stock Exchange, 20 Broad Street, New
York, New York 10005 or at our principal office, 500 South 27th Street, Decatur,
Illinois 62525.
 
                      DOCUMENTS INCORPORATED BY REFERENCE
 
     The Commission allows us to "incorporate by reference" the information we
file with it, which means that we can disclose important information to you by
referring you to those documents. Information incorporated by reference is
considered to be part of this Prospectus. Information that we file with the
Commission after the date of this Prospectus will automatically modify and
supersede the information included or incorporated by reference in this
Prospectus to the extent that the subsequent filings contain information that
modifies or supersedes the existing information. We incorporate by reference the
documents listed below and any future filings made with the Commission under
Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act until we sell all the
Securities.
 
     - Our Annual Report on Form 10-K for the year ended December 31, 1997;
 
     - Our Quarterly Reports on Form 10-Q for the quarters ended March 31, 1998,
       June 30, 1998 (as amended by our Quarterly Report on Form 10-Q/A filed
       August 13, 1998) and September 30, 1998 (as amended by our Quarterly
       Report on Form 10-Q/A filed November 20, 1998); and
 
     - Our Current Reports on Form 8-K dated December 16, 1997, January 21,
       1998, February 13, 1998, April 14, 1998, May 6, 1998, June 24, 1998, July
       6, 1998, July 15, 1998, October 20, 1998, November 25, 1998 and December
       14, 1998.
 
                                        3
<PAGE>   5
 
     We will provide to you (upon receiving your written or oral request) a copy
of any or all of the information that has been or may be incorporated by
reference in, but not delivered with, this Prospectus. We will deliver this
information at no cost to you. You should direct your request to:
 
                             ILLINOIS POWER COMPANY
                        SHAREHOLDER SERVICES DEPARTMENT
                             500 SOUTH 27TH STREET
                            DECATUR, ILLINOIS 62525
                                1(800) 800-8220
                                       OR
                             ILLINOIS POWER COMPANY
                            c/o ILLINOVA CORPORATION
                            http://www.illinova.com.
 
                           FORWARD-LOOKING STATEMENTS
 
     We make statements in this Prospectus and the documents we incorporate by
reference that contain estimates, projections and other forward-looking
statements that involve risks and uncertainties. Actual results or outcomes
could differ materially from those provided in the forward-looking statements as
a result of such important factors as: the outcome of state and federal
regulatory proceedings affecting the restructuring of the electric and gas
utility industries; the impacts of new laws and regulations on Illinova and its
subsidiaries (including the Company) relating to restructuring, environmental
and other matters; the effects of increased competition on the utility
businesses; the risks of owning and operating a nuclear facility; changes in
prices and cost of fuel; factors affecting non-utility investments, such as the
risk of doing business in foreign countries; construction and operation risks;
and increases in financing costs. All forward-looking statements are based upon
information presently available, and we assume no obligation to update any
forward-looking statements.
 
                                  THE COMPANY
 
     We were incorporated under the laws of the State of Illinois on May 25,
1923. We are engaged in the generation, transmission, distribution and sale of
electric energy and the distribution, transportation and sale of natural gas in
the State of Illinois. Our service area is a widely diversified industrial and
agricultural area comprising approximately 15,000 square miles in northern,
central and southern Illinois. We provide electric service at retail to 310
incorporated municipalities, adjacent suburban and rural areas and numerous
unincorporated municipalities having an estimated aggregate population of
approximately 1,265,000. We provide gas service to 257 incorporated
municipalities, adjacent suburban areas and numerous unincorporated
municipalities having an estimated aggregate population of approximately
920,000. The larger cities that we serve include Decatur, East St. Louis (gas
only), Champaign, Danville, Belleville, Granite City, Bloomington (electric
only), Galesburg, Urbana and Normal (electric only). Illinova Corporation owns
all of our outstanding common stock.
 
     Our executive offices are located at 500 South 27th Street, Decatur,
Illinois 62525, and our telephone number is (217) 424-6600.
 
                                USE OF PROCEEDS
 
     We expect to add the net proceeds from the sale of the Securities to our
general funds and use them for general corporate purposes. We may place the net
proceeds in interest-bearing time deposits or invest them in short-term
marketable securities until we use them. If we decide to use the net proceeds of
any offering of Securities in some other way, we will describe the use of the
net proceeds in the Prospectus Supplement for that offering.
 
                                        4
<PAGE>   6
 
                       RATIO OF EARNINGS TO FIXED CHARGES
 
     The following table sets forth our ratios of earnings to fixed charges for
the periods indicated. This information is qualified in its entirety by the
information appearing elsewhere in this Prospectus and incorporated in this
Prospectus by reference.
 
<TABLE>
<CAPTION>
                                                    TWELVE MONTHS
                     YEAR ENDED DECEMBER 31,            ENDED
                 --------------------------------   SEPTEMBER 30,
                 1993   1994   1995   1996   1997       1998
                 ----   ----   ----   ----   ----   -------------
                 <S>    <C>    <C>    <C>    <C>    <C>
                 0.80(1) 2.73  2.77   3.40   0.57(1)     (1.30)(1)
</TABLE>
 
- ---------------
 
(1) Our ratios of earnings to fixed charges of 0.80, 0.57 and (1.30) for the
    years ended December 31, 1993 and 1997 and for the twelve months ended
    September 30, 1998, respectively, indicate that earnings were inadequate to
    cover fixed charges. We required additional earnings of approximately $37
    million in 1993, approximately $62 million in 1997 and approximately $337
    million in the twelve months ended September 30, 1998 to attain a one-to-one
    ratio of earnings to fixed charges. Excluding disallowed Clinton Power
    Station plant costs, our ratio of earnings to fixed charges would have been
    2.25 for the year ended December 31, 1993. Excluding the write-off related
    to the discontinued application of SFAS 71, "Accounting for the Effects of
    Certain Types of Regulation," for the generation segment of our business,
    our ratio of earnings to fixed charges would have been 2.73 for the year
    ended December 31, 1997 and 0.84 for the twelve months ended September 30,
    1998.
 
    Earnings used in the calculation of the ratio of earnings to fixed charges
include the allowance for funds used during construction and the deferred
financing costs associated with our Clinton Power Station and are before
deduction of income taxes and fixed charges. Fixed charges include interest on
long-term debt, related amortization of debt discount, premium, and expense,
other interest and that portion of rent expense which is estimated to be
representative of the interest component.
 
                     DESCRIPTION OF THE NEW MORTGAGE BONDS
 
    The following description applies to any offering of Securities by the
Company consisting of New Mortgage Bonds.
 
GENERAL
 
    The New Mortgage Bonds will be bonds, notes or other evidences of
indebtedness authenticated and delivered under a General Mortgage Indenture and
Deed of Trust between the Company and Harris Trust and Savings Bank (the "New
Mortgage Trustee"), dated as of November 1, 1992. The New Mortgage Bonds will be
issued in one or more series in registered form, without coupons. The General
Mortgage and Deed of Trust, as supplemented by various supplemental indentures,
including one or more supplemental indentures relating to the New Mortgage
Bonds, is referred to in this Prospectus as the "New Mortgage." The summaries
under this heading do not purport to be complete and are subject to the detailed
provisions of the New Mortgage. Capitalized terms used under this heading which
are not otherwise defined in this Prospectus shall have the meanings ascribed
thereto in the New Mortgage. Wherever particular provisions of the New Mortgage
or terms defined therein are referred to, such provisions or definitions are
incorporated by reference as a part of the statements made herein and such
statements are qualified in their entirety by such reference. References to
article and section numbers in this description of the New Mortgage Bonds,
unless otherwise indicated, are references to article and section numbers of the
New Mortgage.
 
    Reference is made to the Prospectus Supplement for a description of the
following terms of each series of New Mortgage Bonds in respect of which this
Prospectus is being delivered:
 
    - the title of such New Mortgage Bonds;
 
    - the limit, if any, upon the aggregate principal amount of such New
      Mortgage Bonds;
 
                                        5
<PAGE>   7
 
     - the date or dates on which the principal of such New Mortgage Bonds is
       payable;
 
     - the rate or rates at which such New Mortgage Bonds will bear interest, if
       any, the date or dates from which such interest will accrue, the dates on
       which such interest will be payable ("Interest Payment Dates"), and the
       regular record dates for the interest payable on such Interest Payment
       Dates;
 
     - the option, if any, of the Company to redeem such New Mortgage Bonds and
       the periods within which or the dates on which, the prices at which and
       the terms and conditions upon which, such New Mortgage Bonds may be
       redeemed, in whole or in part, upon the exercise of such option;
 
     - the obligation, if any, of the Company to redeem or purchase such New
       Mortgage Bonds pursuant to any sinking fund or analogous provisions or at
       the option of the Holder and the periods within which or the dates on
       which, the prices at which and the terms and conditions upon which such
       New Mortgage Bonds will be redeemed or purchased, in whole or in part,
       pursuant to such obligation;
 
     - the denominations in which such New Mortgage Bonds will be issuable;
 
     - whether such New Mortgage Bonds are to be issued in whole or in part in
       the form of one or more global New Mortgage Bonds and, if so, the
       identity of the depositary for such global New Mortgage Bonds; and
 
     - any other terms of such New Mortgage Bonds not inconsistent with the
       provisions of the New Mortgage.
 
REDEMPTION OF THE NEW MORTGAGE BONDS
 
     Any terms for the optional or mandatory redemption of New Mortgage Bonds
will be set forth in the Prospectus Supplement. Except as shall otherwise be
provided in the applicable Prospectus Supplement with respect to New Mortgage
Bonds redeemable at the option of the Holder, New Mortgage Bonds will be
redeemable only upon notice by mail not less than 30 days prior to the date
fixed for redemption, and, if less than all the New Mortgage Bonds of a series,
or any Tranche thereof, are to be redeemed, the particular New Mortgage Bonds to
be redeemed will be selected by such method as shall be provided for any
particular series or Tranche, or in the absence of any such provision, by such
method as the Bond Registrar deems fair and appropriate. (See Sections 5.03 and
5.04.)
 
     Any notice of redemption at the option of the Company may state that such
redemption shall be conditioned upon receipt by the New Mortgage Trustee, on or
prior to the date fixed for such redemption, of money sufficient to pay the
principal of and premium, if any, and interest, if any, on such New Mortgage
Bonds and that if such money has not been so received, such notice will be of no
force and effect and the Company will not be required to redeem such New
Mortgage Bonds. (See Section 5.04.)
 
     While the New Mortgage contains provisions for the maintenance of the
Mortgaged Property, it does not contain any provisions for a maintenance or
sinking fund and, except as may be provided in a Supplemental Indenture (and
described in the applicable Prospectus Supplement) there will be no provisions
for any such funds for the New Mortgage Bonds.
 
SECURITY
 
     General. Except as discussed below, New Mortgage Bonds now or hereafter
issued under the New Mortgage will be secured primarily by:
 
     - if applicable, bonds ("First Mortgage Bonds") issued under the Company's
       Mortgage and Deed of Trust, dated November 1, 1943 (the "First
       Mortgage"), to Harris Trust and Savings Bank, as trustee (the "First
       Mortgage Trustee"), and delivered to the New Mortgage Trustee under the
       New Mortgage; as discussed under "Description of First Mortgage Bonds,"
       the First Mortgage constitutes, subject to certain exceptions, a first
       mortgage lien on substantially all properties of the Company; and
 
                                        6
<PAGE>   8
 
     - the lien of the New Mortgage on the Company's properties used in the
       generation, purchase, transmission, distribution and sale of electricity
       or gas, which lien is junior to the lien of the First Mortgage.
 
     As described below under "Pledged Bonds," following a merger or
consolidation of another corporation into the Company, the Company could deliver
to the New Mortgage Trustee bonds issued under an existing mortgage on the
properties of such other corporation in lieu of or in addition to bonds issued
under the First Mortgage. In such event, the New Mortgage Bonds would be
secured, additionally, by such bonds and by the lien of the New Mortgage on the
properties of such other corporation, which would be junior to the liens of such
existing mortgage and the First Mortgage. The First Mortgage and all such other
mortgages are hereinafter, collectively, called the "Prior Mortgages," and all
bonds issued under the Prior Mortgages and delivered to the New Mortgage Trustee
are hereinafter collectively called the "Pledged Bonds." If and when no Prior
Mortgages are in effect, the New Mortgage will constitute a first mortgage lien
on all property of the Company subject thereto. As described below under
"Pledged Bonds," the only Prior Mortgage at the date of this Prospectus is the
First Mortgage. The Company currently intends to pursue the satisfaction and
discharge of the First Mortgage when the only outstanding First Mortgage Bonds
are Pledged Bonds held by the New Mortgage Trustee. From and after the
satisfaction and discharge of the First Mortgage, the New Mortgage Bonds will
cease to be secured by the Pledged Bonds and instead will be secured primarily
by the lien of the New Mortgage on the Company's properties used in the
generation, purchase, transmission, distribution and sale of electricity or gas.
 
     Pledged Bonds. The Pledged Bonds will be issued and delivered to, and
registered in the name of, the New Mortgage Trustee or its nominee and will be
owned and held by the New Mortgage Trustee, subject to the provisions of the New
Mortgage, for the benefit of the Holders of all New Mortgage Bonds Outstanding
from time to time, and the Company will have no interest in such Pledged Bonds.
Pledged Bonds issued as the basis for the authentication and delivery of New
Mortgage Bonds (a) will mature on the same dates, and in the same principal
amounts, as such New Mortgage Bonds and (b) will contain, in addition to any
mandatory redemption provisions applicable to all Pledged Bonds Outstanding
under the related Prior Mortgage, mandatory redemption provisions correlative to
provisions for mandatory redemption, or for redemption at the option of the
Holder, of such New Mortgage Bonds. Pledged Bonds issued as the basis for
authentication and delivery of a series or Tranche of New Mortgage Bonds (x)
may, but need not, bear interest, any such interest to be payable at the same
times as interest on the New Mortgage Bonds of such series or Tranche and (y)
may, but need not, contain provisions for the redemption thereof at the option
of the Company, any such redemption to be made at a redemption price or prices
not less than the principal amount of such Pledged Bonds. (See Sections 4.02 and
7.01.)
 
     Any payment by the Company of principal of or premium or interest on the
Pledged Bonds held by the New Mortgage Trustee will be applied by the New
Mortgage Trustee to the payment of any principal, premium or interest, as the
case may be, in respect of the New Mortgage Bonds which is then due, and, to the
extent of such application, the obligation of the Company under the New Mortgage
to make such payment in respect of the New Mortgage Bonds will be deemed
satisfied and discharged. If, at the time of any such payment of principal of
Pledged Bonds, there shall be no principal then due in respect of the New
Mortgage Bonds, the proceeds of such payment will be deemed to constitute Funded
Cash and will be held by the New Mortgage Trustee as part of the Mortgaged
Property, to be withdrawn, used or applied as provided in the New Mortgage. If,
at the time of any such payment of premium or interest on Pledged Bonds, there
shall be no premium or interest, as the case may be, then due in respect of the
New Mortgage Bonds, the proceeds of such payments will be remitted to the
Company at its request. (See Section 7.02 and "-- Withdrawal of Cash" below).
Any payment by the Company of principal of or premium or interest on New
Mortgage Bonds authenticated and delivered on the basis of the deposit with the
New Mortgage Trustee of Pledged Bonds (other than by application of the proceeds
of payments in respect of such Pledged Bonds) will, to the extent thereof, be
deemed to satisfy and discharge the obligation of the Company, if any, to make a
payment of principal, premium or interest, as the case may be, in respect of
such Pledged Bonds which is then due.
 
                                        7
<PAGE>   9
 
     The New Mortgage Trustee may not sell, assign or otherwise transfer any
Pledged Bonds except to a successor trustee under the New Mortgage. (See Section
7.04.) At the time any New Mortgage Bonds of any series or Tranche which have
been authenticated and delivered upon the basis of Pledged Bonds cease to be
Outstanding (other than as a result of the application of the proceeds of the
payment or redemption of such Pledged Bonds), the New Mortgage Trustee shall
surrender to or upon the order of the Company an equal principal amount of such
Pledged Bonds having the same Stated Maturity and mandatory redemption
provisions as such New Mortgage Bonds. (See Section 7.03.)
 
     At the date of this Prospectus, the only Prior Mortgage is the First
Mortgage and the only Pledged Bonds issuable at this time are First Mortgage
Bonds issuable thereunder. The New Mortgage provides that in the event of the
merger or consolidation of another company with or into the Company, an existing
mortgage constituting a lien on properties of such other company prior to the
lien of the New Mortgage may be designated by the Company as an additional Prior
Mortgage. Bonds thereafter issued under such additional mortgage would be
Pledged Bonds and could provide the basis for the authentication and delivery of
New Mortgage Bonds under the New Mortgage. (See Section 7.06.) When no Pledged
Bonds are Outstanding under a Prior Mortgage except for Pledged Bonds held by
the New Mortgage Trustee, then, at the request of the Company and subject to
satisfaction of certain conditions, the New Mortgage Trustee will surrender the
Pledged Bonds for cancellation, and the related Prior Mortgage will be satisfied
and discharged, the lien of such Prior Mortgage on the Company's property will
cease to exist and the priority of the lien of the New Mortgage will be
increased. (See Section 7.07.) The Company currently intends to request the New
Mortgage Trustee to surrender the Pledged Bonds for cancellation and to pursue
the satisfaction and discharge of the First Mortgage when the only outstanding
First Mortgage Bonds are Pledged Bonds. There can be no assurance as to whether
and when the Pledged Bonds will be cancelled and the First Mortgage satisfied
and discharged.
 
     The New Mortgage contains no restrictions on the issuance of bonds issued
under Prior Mortgages in addition to Pledged Bonds issued to the New Mortgage
Trustee as the basis for the authentication and delivery of New Mortgage Bonds.
First Mortgage Bonds may currently be issued under the First Mortgage on the
basis of property additions, retirements of bonds previously issued under the
First Mortgage and cash deposited with the First Mortgage Trustee. (See
"Description of First Mortgage Bonds.")
 
     Lien of the New Mortgage. The properties of the Company used in the
generation, purchase, transmission, distribution and sale of electricity and gas
will be subject to the lien of the New Mortgage. Substantially all of such
property, while subject to the lien of the New Mortgage, will be also subject to
the prior lien of the First Mortgage. The New Mortgage Bonds will have the
benefit of the first mortgage lien of the First Mortgage on such property, and
the benefit of the prior lien of any additional Prior Mortgage on any property
subject thereto, to the extent of the aggregate principal amount of Pledged
Bonds, issued under the respective Prior Mortgages, held by the New Mortgage
Trustee. However, as described above, the Company may cancel the Pledged Bonds
issued under the First Mortgage as well as the First Mortgage itself.
 
     The lien of the New Mortgage is subject to Permitted Liens which include
tax liens and other governmental charges which are not delinquent and which are
being contested, construction and material-men's liens, certain judgment liens,
easement, reservations and rights of others (including governmental entities)
in, and defects of title in, certain property of the Company, certain leasehold
interests, liens on the Company's pollution control and sewage and solid waste
facilities and certain other liens and encumbrances. (See Section 1.01.)
 
     There are excepted from the lien of the New Mortgage, among other things:
 
     - cash and securities not paid to, deposited with or held by the New
       Mortgage Trustee under the New Mortgage;
 
     - contracts, leases and other agreements of all kinds, contract rights,
       bills, notes and other instruments, accounts receivable, claims, certain
       intellectual property rights and other general intangibles;
 
     - automobiles, other vehicles, movable equipment, aircraft and vessels;
 
                                        8
<PAGE>   10
 
     - all goods, wares and merchandise held for sale in the ordinary course of
       business or for the use by or the benefit of the Company;
 
     - nuclear fuel;
 
     - fuel, materials, supplies and other personal property consumable in the
       operations of the Company's business;
 
     - computers, machinery and equipment;
 
     - coal, ore, gas, oil, minerals and timber mined or extracted from the
       land;
 
     - electric energy, gas, steam water and other products generated, produced
       or purchased;
 
     - leasehold interests; and
 
     - all books and records.
 
(See Section 1.01.)
 
     Without the consent of the Holders, the Company and the New Mortgage
Trustee may enter into supplemental indentures to subject to the lien of the New
Mortgage additional property, whether or not used in the electric or gas utility
businesses (including property which would otherwise be excepted from such
lien). (See Section 14.01.) Such property, so long as the same would otherwise
constitute Property Additions (as described below), would thereupon constitute
Property Additions and be available as a basis for the issuance of New Mortgage
Bonds. (See "Issuance of Additional New Mortgage Bonds.")
 
     The New Mortgage contains provisions subjecting after-acquired property to
the lien thereof, subject to the prior lien of the First Mortgage. These
provisions are limited in the case of consolidation or merger (whether or not
the Company is the surviving corporation) or sale of substantially all of the
Company's assets. In the event of consolidation or merger or the transfer of all
the mortgaged property as or substantially as an entirety, the New Mortgage will
not be required to be a lien upon any of the properties then owned or thereafter
acquired by the successor corporation except properties acquired from the
Company in or as a result of such transaction and improvements, extensions and
additions to such properties and renewals, replacements and substitutions of or
for any part or parts of such properties. (See Article Thirteen and
"-- Consolidation, Merger, Conveyance, Transfer or Lease.") In addition,
after-acquired property may be subject to vendors' liens, purchase money
mortgages and other liens thereon at the time of acquisition thereof, including
the lien of any Prior Mortgage.
 
     The New Mortgage provides that the New Mortgage Trustee will have a lien,
prior to the lien on behalf of the holders of New Mortgage Bonds, upon Mortgaged
Property, for the payment of its reasonable compensation and expenses and for
indemnity against certain liabilities. (See Section 11.07.)
 
CREDIT ENHANCEMENT
 
     See the Prospectus Supplement for credit enhancement terms, if any, of the
New Mortgage Bonds.
 
ISSUANCE OF ADDITIONAL NEW MORTGAGE BONDS
 
     The maximum principal amount of New Mortgage Bonds which may be issued
under the New Mortgage is unlimited. (See Section 3.01.) New Mortgage Bonds of
any series may be issued from time to time under Article Four of the New
Mortgage on the basis of, and in an aggregate principal amount not exceeding:
 
     - the aggregate principal amount of Pledged Bonds issued and delivered to
       the New Mortgage Trustee;
 
     - 75% of the Cost or Fair Value (whichever is less) of Property Additions
       (as described below) which do not constitute Funded Property (generally,
       Property Additions which have been made the basis of the authentication
       and delivery of New Mortgage Bonds, the release of mortgaged property or
       cash withdrawals, or which have been substituted for retired property)
       after certain deductions and additions, primarily including adjustments
       to offset property retirements;
 
                                        9
<PAGE>   11
 
     - the aggregate principal amount of Retired Bonds (which consist of New
       Mortgage Bonds no longer outstanding under the New Mortgage which have
       not been used for certain other purposes under the New Mortgage and which
       are not to be paid, redeemed or otherwise retired by the application of
       Funded Cash), but if Pledged Bonds had been made the basis for the
       authentication and delivery of such Retired Bonds, only if the related
       Prior Mortgage has been discharged; and
 
     - an amount of cash deposited with the New Mortgage Trustee.
 
     In general, the issuance of New Mortgage Bonds is subject to Adjusted Net
Earnings of the Company for 12 consecutive months within the preceding 18 months
being at least twice the Annual Interest Requirements on all New Mortgage Bonds
at the time outstanding, New Mortgage Bonds then applied for, all outstanding
Prior Bonds other than Pledged Bonds held by the New Mortgage Trustee under the
New Mortgage, and all other indebtedness (with certain exceptions) secured by a
lien prior to the lien of the New Mortgage, except that no such net earnings
requirement need be met if the additional New Mortgage Bonds to be issued are to
have no Stated Interest Rate prior to Maturity. The Company is not required to
satisfy the net earnings requirement prior to issuance of New Mortgage Bonds as
provided in the first bullet point of the preceding paragraph, if the Pledged
Bonds issued and delivered to the New Mortgage Trustee as the basis for such
issuance have been authenticated and delivered under the related Prior Mortgage
on the basis of retired Prior Bonds unless (a) the Stated Maturity of such
retired Prior Bonds is a date more than two years after the date of the Company
Order requesting the authentication and delivery of such New Mortgage Bonds and
(b) the Stated Interest Rate, if any, on such retired Prior Bonds immediately
prior to Maturity is less than the Stated Interest Rate, if any, on such New
Mortgage Bonds to be in effect upon the initial authentication and delivery
thereof. In addition, the Company is not required to satisfy the net earnings
requirement prior to issuance of New Mortgage Bonds as provided in the third
bullet point of the preceding paragraph. In general, the interest requirement
with respect to variable interest rate indebtedness, if any, is determined with
reference to the rate or rates in effect on the date immediately preceding such
determination or the rate to be in effect upon initial authentication. (See
Section 1.03 and Article Four.)
 
     Adjusted Net Earnings are calculated before, among other things, provisions
for income taxes; depreciation or amortization of property; interest on any
indebtedness and amortization of debt discount and expense; any non-recurring
charge to income of whatever kind or nature (including without limitation the
recognition of expense due to the non-recoverability of assets or expense),
whether or not recorded as a non-recurring item in the Company's books of
account; and any refund of revenues previously collected or accrued by the
Company subject to possible refund. Adjusted Net Earnings also do not take into
account profits or losses from the sale or other disposition of property, or
non-recurring charges of any kind or nature, whether items of revenue or
expense. With respect to New Mortgage Bonds of a series subject to a Periodic
Offering (such as a medium-term note program), the New Mortgage Trustee will be
entitled to receive a certificate evidencing compliance with the net earnings
requirements only once, at or prior to the time of the first authentication and
delivery of the New Mortgage Bonds of such series. (See Sections 1.03 and 4.01.)
 
     Property Additions generally include any property which is owned by the
Company and is subject to the lien of the New Mortgage except (with certain
exceptions) goodwill or going concern value rights, or any property the cost of
acquisition or construction of which is properly chargeable to an operating
expense account of the Company. (See Section 1.04.)
 
     Unless otherwise provided in the applicable Prospectus Supplement or
supplement thereto, the Company will issue the New Mortgage Bonds on the basis
of Pledged Bonds (i.e., First Mortgage Bonds) issued under its First Mortgage.
 
RELEASE OF PROPERTY
 
     The Company may obtain the release from the lien of the New Mortgage of any
Funded Property, except for cash held by the New Mortgage Trustee, upon delivery
to the New Mortgage Trustee of cash equal in
 
                                       10
<PAGE>   12
 
amount to the amount, if any, by which the Cost of the property to be released
(or, if less, the Fair Value of such property at the time it became Funded
Property) exceeds the aggregate of:
 
     - the principal amount, subject to certain limitations, of obligations
       secured by purchase money mortgage upon the property to be released
       delivered to the New Mortgage Trustee;
 
     - the Cost or Fair Value (whichever is less) of certified Property
       Additions not constituting Funded Property after certain deductions and
       additions, primarily including adjustments to offset property retirements
       (except that such adjustments need not be made if such Property Additions
       were acquired or made within the 90-day period preceding the release);
 
     - an amount equal to 133 1/3% of the aggregate principal amount of New
       Mortgage Bonds the Company would be entitled to issue on the basis of
       Retired Bonds (with such entitlement being waived by operation of such
       release);
 
     - an amount equal to 133 1/3% of the aggregate principal amount of New
       Mortgage Bonds delivered to the New Mortgage Trustee (with such New
       Mortgage Bonds to be canceled by the New Mortgage Trustee);
 
     - the deposit of cash or, to a limited extent, the principal amount of
       obligations secured by purchase money mortgages upon the property
       released delivered to the trustee or other holder of a lien prior to the
       lien of the New Mortgage; and
 
     - any taxes and expenses incidental to any sale, exchange, dedication or
       other disposition of the property to be released.
 
     Property which is not Funded Property may generally be released from the
lien of the New Mortgage without depositing any cash or property with the New
Mortgage Trustee as long as (a) the aggregate amount of Cost or Fair Value
(whichever is less) of all Property Additions which do not constitute Funded
Property (excluding the property to be released) after certain deductions and
additions, primarily including adjustments to offset property retirements, is
not less than zero or (b) the Cost or Fair Value (whichever is less) of property
to be released does not exceed the aggregate amount of the Cost or Fair Value
(whichever is less) of Property Additions acquired or made within the 90-day
period preceding the release.
 
     The New Mortgage provides simplified procedures for the release of property
which has been released from the lien of a Prior Mortgage, minor properties and
property taken by eminent domain, and provides for dispositions of certain
obsolete property and grants or surrender of certain rights without any release
or consent by the New Mortgage Trustee.
 
     If any property released from the lien of the New Mortgage continues to be
owned by the Company after such release, the New Mortgage will not become a lien
on any improvement, extension or addition to such property or renewals,
replacements or substitutions of or for any part or parts of such property. (See
Article Eight.)
 
WITHDRAWAL OF CASH
 
     Subject to certain limitations, cash held by the New Mortgage Trustee may
(1) be withdrawn by the Company (a) to the extent of the Cost or Fair Value
(whichever is less) of Property Additions not constituting Funded Property,
after certain deductions and additions, primarily including adjustments to
offset retirements or (b) in an amount equal to 133 1/3% of the aggregate
principal amount of New Mortgage Bonds that the Company would be entitled to
issue on the basis of Retired Bonds (with such entitlement being waived by
operation of such withdrawal) or (c) in an amount equal to 133 1/3% of the
aggregate principal amount of any Outstanding New Mortgage Bonds delivered to
the New Mortgage Trustee, or (2) upon the request of the Company, be applied to
(a) the purchase of New Mortgage Bonds (at prices not exceeding 133 1/3% of the
principal amount thereof) or (b) the redemption or payment at Stated Maturity of
New Mortgage Bonds (with any New Mortgage Bonds received by the New Mortgage
Trustee pursuant to these provisions being cancelled by the New Mortgage
Trustee) (see Section 8.06); provided, however, that cash
 
                                       11
<PAGE>   13
 
deposited with the New Mortgage Trustee as the basis for the authentication and
delivery of New Mortgage Bonds, as well as cash representing a payment of
principal of Pledged Bonds, may only be withdrawn in an amount equal to the
aggregate principal amount of New Mortgage Bonds the Company would be entitled
to issue on any basis (with such entitlement being waived by operation of such
withdrawal), or may, upon the request of the Company, be applied to the
purchase, redemption or payment of New Mortgage Bonds at prices not exceeding,
in the aggregate, the principal amount thereof. (See Sections 4.05 and 7.02.)
 
CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE
 
     The Company may not consolidate with or merge into any other corporation or
convey, transfer or lease the Mortgaged Property as or substantially as an
entirety to any Person unless (a) such transaction is on such terms as will
fully preserve in all material respects the lien and security of the New
Mortgage and the rights and powers of the New Mortgage Trustee and Holders, (b)
the corporation formed by such consolidation or into which the Company is merged
or the Person which acquires by conveyance or transfer, or which leases, the
Mortgaged Property as or substantially as an entirety is a corporation organized
and existing under the laws of the United States of America or any State or
Territory thereof or the District of Columbia, and such corporation executes and
delivers to the New Mortgage Trustee a supplemental indenture, which contains an
assumption by such corporation of the due and punctual payment of the principal
of and premium, if any, and interest, if any, on the New Mortgage Bonds and the
performance of all of the covenants of the Company under the New Mortgage and
which contains a grant, conveyance, transfer and mortgage by the corporation
confirming the lien of the New Mortgage on the Mortgaged Property and subjecting
to such lien all property thereafter acquired by the corporation which shall
constitute an improvement, extension or addition to the Mortgaged Property or a
renewal, replacement or substitution of or for any part thereof, and, at the
election of the corporation, subjecting to the lien of the New Mortgage such
other property then owned or thereafter acquired by the corporation as the
corporation shall specify and (c) in the case of a lease, such lease will be
made expressly subject to termination by the Company or the New Mortgage Trustee
at any time during the continuance of an Event of Default. (See Section 13.01.)
 
MODIFICATION OF NEW MORTGAGE
 
     Without the consent of any Holders, the Company and the New Mortgage
Trustee may enter into one or more supplemental indentures for any of the
following purposes:
 
     - to evidence the succession of another Person to the Company and the
       assumption by any such successor of the covenants of the Company in the
       New Mortgage and in the New Mortgage Bonds; or
 
     - to add one or more covenants of the Company or other provisions for the
       benefit of all Holders or for the benefit of the Holders of, or to remain
       in effect only so long as there shall be Outstanding, New Mortgage Bonds
       of one or more specified series, or one or more Tranches thereof, or to
       surrender any right or power conferred upon the Company by the New
       Mortgage; or
 
     - to correct or amplify the description of any property at any time subject
       to the lien of the New Mortgage, or better to assure, convey and confirm
       to the New Mortgage Trustee any property subject or required to be
       subjected to the lien of the New Mortgage, or to subject to the lien of
       the New Mortgage additional property; or
 
     - to convey, transfer and assign to the New Mortgage Trustee and to subject
       to the Lien of the New Mortgage with the same force and effect as if
       included in the New Mortgage, property of subsidiaries of the Company
       used or to be used for one or more purposes which if owned by the Company
       would constitute property used or to be used for one or more of the
       Primary Purposes of the Company's business, which property shall for all
       purposes of the New Mortgage be deemed to be property of the Company,
       together with such other provisions as may be appropriate to express the
       respective rights of the New Mortgage Trustee and the Company in regard
       thereto; or
 
     - to change or eliminate any provision of the New Mortgage or to add any
       new provision to the New Mortgage, provided that if such change,
       elimination or addition adversely affects the interests of the
 
                                       12
<PAGE>   14
 
       Holders of the New Mortgage Bonds of any series or Tranche in any
       material respect, such change, elimination or addition will become
       effective with respect to such series or Tranche only when no New
       Mortgage Bond of such series or Tranche remains outstanding under the New
       Mortgage; or
 
     - to establish the form or terms of the New Mortgage Bonds of any series or
       Tranche as permitted by the New Mortgage; or
 
     - to provide for the authentication and delivery of bearer securities and
       coupons appertaining thereto representing interest, if any, thereon and
       for the procedures for the registration, exchange and replacement thereof
       and for the giving of notice to, and the solicitation of the vote or
       consent of, the holders thereof, and for any and all other matters
       incidental thereto; or
 
     - to evidence and provide for the acceptance of appointment by a successor
       trustee or by a co-trustee or separate trustee; or
 
     - to provide for the procedures required to permit the utilization of a
       noncertificated system of registration for all, or any series or tranche
       of, the New Mortgage Bonds; or
 
     - to change any place where (a) the principal of and premium, if any, and
       interest, if any, on the New Mortgage Bonds of any series, or any Tranche
       thereof, will be payable, (b) any New Mortgage Bonds of any series, or
       any Tranche thereof, may be surrendered for registration of transfer, (c)
       any New Mortgage Bonds of any series, or any Tranche thereof, may be
       surrendered for exchange and (d) notices and demands to or upon the
       Company in respect of the New Mortgage Bonds of any series, or any
       Tranche thereof, and the New Mortgage may be served; or
 
     - to cure any ambiguity, to correct or supplement any provision therein
       which may be defective or inconsistent with any other provision therein,
       or to make any changes to the provisions thereof or to add other
       provisions with respect to matters and questions arising under the New
       Mortgage, so long as such other changes or additions do not adversely
       affect the interests of the Holders of New Mortgage Bonds of any series
       or Tranche in any material respect; or
 
     - to reflect changes in Generally Accepted Accounting Principles; or
 
     - to provide the terms and conditions of the exchange or conversion, at the
       option of the holders of New Mortgage Bonds of any series, of the New
       Mortgage Bonds of such series for or into New Mortgage Bonds of other
       series or stock or other securities of the Company or any other
       corporation; or
 
     - to change the words "Mortgage Bonds" to "First Mortgage Bonds" in the
       descriptive title of all Outstanding New Mortgage Bonds at any time after
       the discharge of the First Mortgage; or
 
     - to comply with the rules or regulations of any national securities
       exchange on which any of the New Mortgage Bonds may be listed.
 
(See Section 14.01.)
 
     Without limiting the generality of the foregoing, if the Trust Indenture
Act of 1939, as amended (the "Trust Indenture Act"), is amended after the date
of the New Mortgage in such a way as to require changes to the New Mortgage or
the incorporation therein of additional provisions or so as to permit changes
to, or the elimination of, provisions which, at the date of the New Mortgage or
at any time thereafter, were required by the Trust Indenture Act to be contained
in the New Mortgage, the Company and the New Mortgage Trustee may, without the
consent of any Holders, enter into one or more supplemental indentures to
evidence or effect such amendment. (See Section 14.01.)
 
     Except as provided above, the consent of the Holders of a majority in
aggregate principal amount of the New Mortgage Bonds of all series then
Outstanding, considered as one class, is required for the purpose of adding any
provisions to, or changing in any manner, or eliminating any of the provisions
of, the New Mortgage pursuant to one or more supplemental indentures; provided,
however, if less than all of the series of New Mortgage Bonds Outstanding are
directly affected by a proposed supplemental indenture, then the consent only of
the Holders of a majority in aggregate principal amount of Outstanding New
Mortgage Bonds
                                       13
<PAGE>   15
 
of all series so directly affected, considered as one class, will be required;
and provided, further, that if the New Mortgage Bonds of any series have been
issued in more than one Tranche and if the proposed supplemental indenture
directly affects the rights of the Holders of one or more, but less than all,
such Tranches, then the consent only of the Holders of a majority in aggregate
principal amount of the Outstanding New Mortgage Bonds of all Tranches so
directly affected, considered as one class, will be required; and provided,
further, that no such amendment or modification may, without the consent of each
Holder of the Outstanding New Mortgage Bonds of each series or Tranche directly
affected thereby:
 
     - change the Stated Maturity of the principal of, or any installment of
       principal of or interest on, any New Mortgage Bond, or reduce the
       principal amount thereof or the rate of interest thereon (or the amount
       of any installment of interest thereon) or change the method of
       calculating such rate or reduce any premium payable upon the redemption
       thereof, or reduce the amount of the principal of a Discount Bond that
       would be due and payable upon a declaration of acceleration of maturity
       or change the coin or currency (or other property) in which any New
       Mortgage Bond or any premium or the interest thereon is payable, or
       impair the right to institute suit for the enforcement of any such
       payment on or after the Stated Maturity thereof (or, in the case of
       redemption, on or after the redemption date);
 
     - permit the creation of any lien ranking prior to the lien of the New
       Mortgage with respect to all or substantially all of the Mortgaged
       Property or terminate the lien of the New Mortgage on all or
       substantially all of the Mortgaged Property, or deprive such Holder of
       the benefit of the security of the lien of the New Mortgage:
 
     - reduce the percentage in principal amount of the Outstanding New Mortgage
       Bonds of such series or Tranche, the consent of the Holders of which is
       required for any such supplemental indenture, or the consent of the
       Holders of which is required for any waiver of compliance with any
       provision of the New Mortgage or of any default thereunder and its
       consequences, or reduce the requirements for quorum or voting; or
 
     - modify certain of the provisions of the New Mortgage relating to
       supplemental indentures, waivers of certain covenants and waivers of past
       defaults.
 
A supplemental indenture which changes or eliminates any covenant or other
provision of the New Mortgage which has expressly been included solely for the
benefit of the Holders of, or which is to remain in effect only so long as there
shall be Outstanding New Mortgage Bonds of one or more specified series, or one
or more Tranches thereof, or modifies the rights of the Holders of New Mortgage
Bonds of such series or Tranches with respect to such covenant or other
provision, will be deemed not to affect the rights under the New Mortgage of the
Holders of the New Mortgage Bonds of any other series or Tranche. (See Section
14.02.)
 
WAIVER
 
     The Holders of a majority in aggregate principal amount of all New Mortgage
Bonds may waive the Company's obligations to comply with certain covenants,
including the Company's obligation to maintain its corporate existence and
properties, pay taxes and discharge liens, maintain certain insurance and to
make such recordings and filings as are necessary to protect the security of the
Holders and the rights of the New Mortgage Trustee, provided that such waiver
occurs before the time such compliance is required. The Holders of a majority of
the aggregate principal amount of Outstanding New Mortgage Bonds of all affected
series or Tranches, considered as one class, may waive, before the time for such
compliance, compliance with the Company's obligations to maintain an office or
agency where the New Mortgage Bonds of such series or Tranches may be
surrendered for payment, registration, transfer or exchange, and compliance with
any other covenant specified in a supplemental indenture respecting such series
or Tranches. (See Section 6.09.)
 
                                       14
<PAGE>   16
 
EVENTS OF DEFAULT
 
     Each of the following events constitutes an Event of Default under the New
Mortgage:
 
     - failure to pay interest on any New Mortgage Bond within 45 days after the
       same becomes due;
 
     - failure to pay principal of or premium, if any, on any New Mortgage Bond
       within three business days after its Maturity;
 
     - failure to perform or breach of any covenant or warranty of the Company
       in the New Mortgage (other than a covenant or warranty a default in the
       performance of which or breach of which is dealt with elsewhere under
       this paragraph) for a period of 60 days after there has been given to the
       Company by the New Mortgage Trustee, or to the Company and the New
       Mortgage Trustee by the Holders of at least 25% in principal amount of
       Outstanding New Mortgage Bonds, a written notice specifying such default
       or breach and requiring it to be remedied and stating that such notice is
       a "Notice of Default," unless the New Mortgage Trustee, or the New
       Mortgage Trustee and the Holders of a principal amount of New Mortgage
       Bonds not less than the principal amount of New Mortgage Bonds the
       Holders of which gave such notice, as the case may be, agree in writing
       to an extension of such period prior to its expiration; provided,
       however, that the New Mortgage Trustee, or the New Mortgage Trustee and
       such Holders, as the case may be, will be deemed to have agreed to an
       extension of such period if corrective action has been initiated by the
       Company within such period and is being diligently pursued;
 
     - certain events relating to reorganization, bankruptcy or insolvency of
       the Company or the appointment of a receiver or trustee for its property;
       or
 
     - the occurrence of a Matured Event of Default under any Prior Mortgage;
       provided that the waiver or cure of any such event of default and the
       rescission and annulment of the consequences thereof will constitute a
       waiver of the corresponding Event of Default under the New Mortgage and a
       rescission and annulment of the consequences thereof.
 
(See Section 10.01.)
 
REMEDIES
 
     If an Event of Default occurs and is continuing, then the New Mortgage
Trustee or the Holders of not less than 33% in principal amount of New Mortgage
Bonds then Outstanding may declare the principal amount (or if any of the New
Mortgage Bonds are Discount Bonds, such portion of the principal amount as may
be provided for such Discount Bonds pursuant to the terms of the New Mortgage)
of all of the New Mortgage Bonds, together with the premium, if any, and
interest accrued, if any, thereon to be immediately due and payable. At any time
after such declaration of the maturity of the New Mortgage Bonds then
Outstanding, but before the sale of any of the Mortgaged Property and before a
judgment or decree for payment of money shall have been obtained by the New
Mortgage Trustee as provided in the New Mortgage, the Event or Events of Default
giving rise to such declaration of acceleration will, without further act, be
deemed to have been waived, and such declaration and its consequences will,
without further act, be deemed to have been rescinded and annulled, if:
 
     - the Company has paid or deposited with the New Mortgage Trustee a sum
       sufficient to pay:
 
          - all overdue interest, if any, on all New Mortgage Bonds then
            Outstanding;
 
          - the principal of and premium, if any, on any New Mortgage Bonds then
            Outstanding which have become due otherwise than by such declaration
            of acceleration and interest thereon at the rate or rates prescribed
            therefor in such New Mortgage Bonds; and
 
          - all amounts due to the New Mortgage Trustee as compensation and
            reimbursement as provided in the New Mortgage; and
 
                                       15
<PAGE>   17
 
     - any other Event or Events of Default, other than the non-payment of the
       principal of New Mortgage Bonds which shall have become due solely by
       such declaration of acceleration, shall have been cured or waived as
       provided in the New Mortgage.
 
(See Sections 10.02 and 10.17.)
 
     The New Mortgage provides that, under certain circumstances and to the
extent permitted by law, if an Event of Default occurs and is continuing, the
New Mortgage Trustee has the power to take possession of, and to hold, operate
and manage, the Mortgaged Property, or with or without entry, to sell the
Mortgaged Property. If the Mortgaged Property is sold, whether by the New
Mortgage Trustee or pursuant to judicial proceedings, the principal of the
Outstanding New Mortgage Bonds, if not previously due, will become immediately
due, together with premium, if any, and any accrued interest. (See Sections
10.03, 10.04 and 10.05.)
 
     If an Event of Default occurs and is continuing, the Holders of a majority
in principal amount of the New Mortgage Bonds then Outstanding will have the
right to direct the time, method and place of conducting any proceedings for any
remedy available to the New Mortgage Trustee or exercising any trust or power
conferred on the New Mortgage Trustee, provided that (a) such direction does not
conflict with any rule of law or with the New Mortgage, and could not involve
the New Mortgage Trustee in personal liability in circumstances where indemnity
would not, in the New Mortgage Trustee's sole discretion, be adequate and (b)
the New Mortgage Trustee may take any other actions deemed proper by the New
Mortgage Trustee which is not inconsistent with such discretion. (See Section
10.16.)
 
     The New Mortgage provides that no Holder of any New Mortgage Bond will have
any right to institute any proceeding, judicial or otherwise, with respect to
the New Mortgage or the appointment of a receiver or trustee, or for any other
remedy thereunder unless (a) such Holder has previously given to the New
Mortgage Trustee written notice of a continuing Event of Default; (b) the
Holders of a majority in aggregate principal amount of the New Mortgage Bonds
then Outstanding have made written request to the New Mortgage Trustee to
institute proceedings in respect of such Event of Default and have offered the
New Mortgage Trustee reasonable indemnity against costs and liabilities incurred
in complying with such request; and (c) for sixty days after receipt of such
notice, the New Mortgage Trustee has failed to institute any such proceeding and
no direction inconsistent with such request has been given to the New Mortgage
Trustee during such sixty-day period by the Holders of a majority in aggregate
principal amount of New Mortgage Bonds then Outstanding. Furthermore, no Holder
will be entitled to institute any such action if and to the extent that such
action would disturb or prejudice the rights of other Holders. (See Section
10.11.) Notwithstanding that the right of a Holder to institute a proceeding
with respect to the New Mortgage is subject to certain conditions precedent,
each Holder of a New Mortgage Bond has the right, which is absolute and
unconditional, to receive payment of the principal of and premium, if any, and
interest, if any, on such New Mortgage Bond when due and to institute suit for
the enforcement of any such payment, and such rights may not be impaired without
the consent of such Holder. (See Section 10.12.) The New Mortgage provides that
the New Mortgage Trustee must give the Holders notice of any default under the
New Mortgage to the extent required by the Trust Indenture Act, unless such
default shall have been cured or waived, except that no such notice to Holders
of a default of the character described in the third bullet point under
"-- Events of Default" may be given until at least 45 days after the occurrence
thereof. (See Section 11.02.) The Trust Indenture Act currently permits the New
Mortgage Trustee to withhold notices of default (except for certain payment
defaults) if the New Mortgage Trustee in good faith determines the withholding
of such notice to be in the interest of the Holders.
 
     As a condition precedent to certain actions by the New Mortgage Trustee in
the enforcement of the lien of the New Mortgage and institution of action on the
New Mortgage Bonds, the New Mortgage Trustee may require adequate indemnity
against costs, expenses and liabilities to be incurred in connection therewith.
(See Sections 10.11 and 11.01.)
 
     In addition to every other right and remedy provided in the New Mortgage,
the New Mortgage Trustee may exercise any right or remedy available to the New
Mortgage Trustee in its capacity as owner and holder
 
                                       16
<PAGE>   18
 
of Pledged Bonds which arises as a result of a default or Matured Event of
Default under any Prior Mortgage, whether or not an Event of Default under the
New Mortgage has occurred and is continuing. (See Section 10.20.)
 
DEFEASANCE
 
     Any New Mortgage Bond or Bonds, or any portion of the principal amount
thereof, will be deemed to have been paid for purposes of the New Mortgage and
the entire indebtedness of the Company in respect thereof will be deemed to have
been satisfied and discharged, if there has been irrevocably deposited with the
New Mortgage Trustee, in trust: (a) money in the amount which will be
sufficient, or (b) Eligible Obligations (as described below) which do not
contain provisions permitting the redemption or other prepayment thereof at the
option of the issuer thereof, the principal of and the interest on which when
due, without any regard to reinvestment thereof, will provide monies which will
be sufficient, or (c) a combination of (a) and (b) which will be sufficient, to
pay when due the principal of and premium, if any, and interest, if any, due and
to become due on such New Mortgage Bond or Bonds or portions thereof. (See
Section 9.01.) For this purpose, Eligible Obligations include direct obligations
of, or obligations unconditionally guaranteed by, the United States of America,
entitled to the benefit of the full faith and credit thereof, and certificates,
depositary receipts or other instruments which evidence a direct ownership
interest in such obligations or in any specific interest or principal payments
due in respect thereof.
 
RESIGNATION AND REMOVAL OF THE NEW MORTGAGE TRUSTEE
 
     The New Mortgage Trustee may resign at any time by giving written notice
thereof to the Company or may be removed at any time by Act of the Holders of a
majority in principal amount of New Mortgage Bonds then Outstanding delivered to
the New Mortgage Trustee and the Company. No resignation or removal of the New
Mortgage Trustee and no appointment of a successor trustee will become effective
until the acceptance of appointment by a successor trustee in accordance with
the requirements of the New Mortgage. So long as no Event of Default or event
which, after notice or lapse of time, or both, would become an Event of Default
has occurred and is continuing, if the Company has delivered to the New Mortgage
Trustee a resolution of its Board of Directors appointing a successor trustee
and such successor has accepted such appointment in accordance with the terms of
the New Mortgage, the New Mortgage Trustee will be deemed to have resigned and
the successor will be deemed to have been appointed as trustee in accordance
with the New Mortgage. (See Section 11.10.)
 
CONCERNING THE NEW MORTGAGE TRUSTEE
 
     Harris Trust and Savings Bank, the Trustee under the New Mortgage, has been
a regular depositary of funds of the Company. From time to time the Company
borrows funds on a short-term basis from Harris Trust and Savings Bank. As
trustee under both the New Mortgage and the First Mortgage, Harris Trust and
Savings Bank would have a conflicting interest for purposes of the Trust
Indenture Act if an Event of Default were to occur under either mortgage. In
that case, the New Mortgage Trustee may be required to eliminate such
conflicting interest by resigning either as New Mortgage Trustee or as First
Mortgage Trustee. There are other instances under the Trust Indenture Act which
would require the resignation of the New Mortgage Trustee if an Event of Default
were to occur, such as an affiliate of the New Mortgage Trustee acting as
underwriter with respect to any of the New Mortgage Bonds.
 
TRANSFER
 
     The transfer of New Mortgage Bonds may be registered, and New Mortgage
Bonds may be exchanged for other New Mortgage Bonds of the same series and
Tranche, of authorized denominations and of like tenor and aggregate principal
amount, at the office of Harris Trust and Savings Bank, of Chicago, Illinois, as
Bond Registrar for the New Mortgage Bonds. The Company may change the place for
registration of transfer of the New Mortgage Bonds, may appoint one or more
additional Bond Registrars (including the Company) and may remove any Bond
Registrar, all at its discretion. (See Section 6.02.) The applicable Prospectus
Supplement, or a supplement thereto, will identify any new place for
registration of transfer and any additional

                                       17
<PAGE>   19
 
Bond Registrar appointed, and will disclose the removal of any Bond Registrar
effected, prior to the date of such Prospectus Supplement, or supplement
thereto. Except as otherwise provided in the applicable Prospectus Supplement,
no service charge will be made for any transfer or exchange of the New Mortgage
Bonds, but the Company may require payment of a sum sufficient to cover any tax
or other governmental charge that may be imposed in connection with any
registration of transfer or exchange of the New Mortgage Bonds. The Company will
not be required to issue and no Bond Registrar will be required to register the
transfer of or to exchange (a) New Mortgage Bonds of any series (including the
New Mortgage Bonds) during a period of 15 days prior to giving any notice of
redemption or (b) any New Mortgage Bond selected for redemption in whole or in
part, except the unredeemed portion of any New Mortgage Bond being redeemed in
part. (See Section 3.05.)
 
DESCRIPTION OF FIRST MORTGAGE BONDS
 
     General. The following statements are brief summaries of certain provisions
of the First Mortgage and supplemental indentures, which are filed as exhibits
to the Registration Statement, and do not purport to be complete. They make use
of defined terms (including those appearing herein in italics) and are qualified
in their entirety by the references to provisions of the First Mortgage and
supplemental indentures, which provisions are incorporated in these summaries by
such references. The parenthetical references in this "-- Description of First
Mortgage Bonds" are to the Articles in Roman numerals and Sections in Arabic
numerals of the First Mortgage ("M").
 
     Security. The First Mortgage Bonds will be secured, equally and ratably
(except as to any sinking or similar fund established for a particular series of
bonds) with all other bonds issued under the First Mortgage, by a valid first
mortgage lien on substantially all of the fixed property, franchises and rights
of the Company, subject to certain exceptions.
 
     Limitations and Restrictions on Dividends. Certain supplemental indentures
to the First Mortgage dated on or after July 1, 1949 contain covenants
restricting the payment of dividends. None of the approximately $57 million of
retained earnings of the Company at September 30, 1998 were restricted by these
covenants.
 
     Sinking and Property Fund; Other Sinking Funds. Certain supplemental
indentures to the First Mortgage dated on or after July 1, 1949 provide for
annual cash deposits for Sinking and Property Funds for the bonds outstanding
thereunder, respectively, in each case beginning with the eleventh year after
the date of issuance, the overall effect of which is that the annual aggregate
requirements under all of such Sinking and Property Funds shall not exceed 1% of
the total First Mortgage Bonds of the various then outstanding series
theretofore issued.
 
     Maintenance and Renewal Fund. Certain supplemental indentures to the First
Mortgage dated on or after July 1, 1949 require the Company to deposit in cash
with the First Mortgage Trustee each year the amount of $2,000,000 plus 2 1/4%
of net property additions from January 1, 1946, which amount may be reduced in
any year by the principal amount of bonds of any series surrendered to the First
Mortgage Trustee for cancellation, or by application of the lesser of cost or
fair value of gross property additions not subject to an unfunded prior lien
acquired during the preceding calendar year.
 
     Issuance of Additional First Mortgage Bonds. Additional bonds of any series
may be issued under the First Mortgage in a principal amount equal to (1) 75% of
the net bondable value of property additions not subject to an unfunded prior
lien; (2) the principal amount of bonds retired other than out of trust estate
moneys; and (3) the amount of cash deposited with the First Mortgage Trustee for
such purpose (which may thereafter be withdrawn upon the same basis that
additional bonds are issuable under (1) and (2) above) but in each case only if
net earnings available for interest and property retirement appropriations for
12 consecutive months within the 18 months immediately preceding the month in
which application for such additional bonds is made, shall have been equal to at
least two times annual interest charges on all bonds which will be outstanding
under the First Mortgage immediately after the issue of the additional bonds
applied for and all prior lien bonds, if any, except that no net earnings
requirements are applicable (i) to the withdrawal of cash so deposited, or (ii)
to the issuance of additional bonds to refund bonds of any series at or within
two years of
 
                                       18
<PAGE>   20
 
their maturity if all or substantially all of such additional bonds or their
proceeds of sale will be applied to such refunding or to the payment of moneys
borrowed for such purpose. (M III 3, 4, 5 and 6 and VIII 3)
 
     Defaults. Defaults are defined to include:
 
     - the failure to pay interest on any bond within 45 days after the same
       becomes due;
 
     - the failure to pay the principal of or premium, if any, on any bond
       within three business days after its maturity;
 
     - the failure to make any payment to any sinking, maintenance or analogous
       fund within 60 days after the same becomes due;
 
     - a breach of the terms of the covenant relating to dividends, or failure
       for 60 days after notice to perform any other covenant, agreement or
       condition contained in the First Mortgage or any supplemental indenture
       or in the bonds;
 
     - certain events of bankruptcy, receivership and similar proceedings; and
 
     - the occurrence of an Event of Default under the New Mortgage or a Matured
       Event of Default under any Prior Mortgage; provided that the waiver or
       cure of any such Event of Default or Matured Event of Default shall
       constitute a waiver of the default and the rescission and annulment of
       the consequences thereof.
 
(M IX 1)
 
     Each bondholder has the absolute and unconditional right to enforce the
payment of principal of and interest on his bonds at or after the maturity
thereof. (M IX 12) The holders of 25% or more of the outstanding bonds, or the
First Mortgage Trustee, may declare the principal of all outstanding bonds due
upon the happening of any of the events of default, but holders of a majority of
the outstanding bonds may waive any such default and rescind any such
declaration, whether made by the First Mortgage Trustee or holders of 25% or
more of the outstanding bonds, if all defaults (other than payment of principal
due on account of such declaration) have been made good or secured to the
satisfaction of the First Mortgage Trustee or provision deemed by the First
Mortgage Trustee to be adequate shall be made therefor. Any waiver does not
affect any subsequent default. (M IX 1) The holders of a majority of the
outstanding bonds may, upon the happening of any of the events of default,
direct the First Mortgage Trustee to enforce payment of the bonds and the lien
of the First Mortgage. (M IX 4) The First Mortgage Trustee is under no
obligation to exercise any of its trusts or powers at the request of the
bondholders unless such bondholders have offered adequate indemnity against
costs, expenses and liabilities to be incurred thereby. (M XIII 1)
 
     Within 90 days after the close of each fiscal year, the Company is required
to furnish to the First Mortgage Trustee an officer's certificate as to the
absence of default and as to compliance with the terms of the First Mortgage. (M
IV 8)
 
     Concerning the First Mortgage Trustee. Harris Trust and Savings Bank, the
Trustee under the First Mortgage, has been a regular depositary of funds of the
Company. From time to time the Company borrows funds on a short-term basis from
Harris Trust and Savings Bank. As trustee under both the New Mortgage and the
First Mortgage, Harris Trust and Savings Bank would have a conflicting interest
under the Trust Indenture Act if an Event of Default were to occur under either
mortgage. In that case, the First Mortgage Trustee may be required to eliminate
such conflicting interest by resigning either as First Mortgage Trustee or as
New Mortgage Trustee. There are other instances under the Trust Indenture Act
which would require the resignation of the First Mortgage Trustee if an Event of
Default were to occur, such as an affiliate of the First Mortgage Trustee acting
as underwriter with respect to any First Mortgage Bonds.
 
     Modification. The First Mortgage may be modified with the consent of the
holders of at least 66 2/3% in amount of the bonds outstanding under the First
Mortgage, and at least 66 2/3% in amount of each series affected, if less than
all series are affected, except that no modification is permitted which will
affect the terms of payment of the principal of, or premium, if any, or interest
on, any bond issued under the First Mortgage.
 
                                       19
<PAGE>   21
 
(M XV 6) As described more fully in "Description of New Mortgage Bonds," First
Mortgage Bonds may be issued to the New Mortgage Trustee as security for New
Mortgage Bonds.
 
                  DESCRIPTION OF THE UNSECURED DEBT SECURITIES
 
     The following description applies to any offering of Securities by the
Company consisting of unsecured debentures, notes or other evidences of
indebtedness (the "Unsecured Debt Securities").
 
GENERAL
 
     The Unsecured Debt Securities are to be issued under an Indenture dated as
of July 15, 1986 (the "Indenture"), between the Company and The Chase Manhattan
Bank (the successor to Chemical Bank), as Trustee, as supplemented by one or
more Supplemental Indentures relating to the Unsecured Debt Securities. A copy
of the Indenture has been filed as an exhibit to the Registration Statement
under which the Securities are registered. The following summary does not
purport to be complete, and where particular provisions of the Indenture are
referred to, such provisions, including definitions of certain terms, are
incorporated by reference as a part of such summary, which is qualified in its
entirety by such reference.
 
     The Indenture does not limit the amount of Unsecured Debt Securities which
can be issued thereunder and provides that Unsecured Debt Securities may be
issued thereunder in one or more series up to the aggregate principal amount
which may be authorized from time to time by the Company.
 
     Reference is made to the Prospectus Supplement for a description of the
following terms of each series of Unsecured Debt Securities in respect of which
this Prospectus is being delivered:
 
     - the title of such Unsecured Debt Securities;
 
     - the limit, if any, upon the aggregate principal amount of such Unsecured
       Debt Securities;
 
     - the date or dates on which the principal of such Unsecured Debt
       Securities is payable;
 
     - the rate or rates at which such Unsecured Debt Securities will bear
       interest, if any, the date or dates from which such interest will accrue,
       the dates on which such interest will be payable, and the regular record
       dates for the interest payable on such interest payment dates;
 
     - the option, if any, of the Company to redeem such Unsecured Debt
       Securities and the periods within which or the dates on which, the prices
       at which and the terms and conditions upon which, such Unsecured Debt
       Securities may be redeemed, in whole or in part, upon the exercise of
       such option;
 
     - the obligation, if any, of the Company to redeem or purchase such
       Unsecured Debt Securities pursuant to any sinking fund or analogous
       provisions or at the option of the holder and the periods within which or
       the dates on which, the prices at which and the terms and conditions upon
       which such Unsecured Debt Securities will be redeemed or purchased, in
       whole or in part, pursuant to such obligation;
 
     - the denominations in which such Unsecured Debt Securities will be
       issuable;
 
     - whether such Unsecured Debt Securities are to be issued in whole or in
       part in the form of one or more global Unsecured Debt Securities and, if
       so, the identity of the depositary for such global Unsecured Debt
       Securities; and
 
     - any other terms of such Unsecured Debt Securities not inconsistent with
       the provisions of the Indenture.
 
     The Amended and Restated Articles of Incorporation of the Company limit the
amount of unsecured indebtedness that the Company may issue or assume, without
the consent of the holders of a majority of the total number of shares of
Preferred Stock then outstanding, to 20% of the aggregate of the total principal
amount of all outstanding First Mortgage Bonds or other securities representing
secured indebtedness of the Company and the capital and surplus of the Company
as then stated on the Company's books.
 
                                       20
<PAGE>   22
 
     Except as may otherwise be set forth in the Prospectus Supplement, the
Company has designated the office of the Trustee in the Borough of Manhattan,
the City of New York (currently 450 West 33rd Street, 15th Floor, New York, New
York 10001-2697) as the place at which principal of and the premium, if any, and
the interest on the Unsecured Debt Securities will be payable and at which
Unsecured Debt Securities may be presented for registration of transfer and for
exchange for a like series of Unsecured Debt Securities of different
denominations, provided that payment of any interest may be made at the option
of the Company by check mailed to the registered holders of the Unsecured Debt
Securities at their registered addresses. (See Sections 2.01, 2.03 and 4.03)
 
     The Unsecured Debt Securities will be issued only in fully registered
certificated or book-entry form without coupons. The Company may charge a
reasonable fee for any transfer or exchange of the Unsecured Debt Securities,
with certain exceptions. (See Section 2.06)
 
     The Unsecured Debt Securities will be unsecured and will rank pari passu
with all other unsecured and unsubordinated indebtedness of the Company. The
Indenture does not restrict the amount of additional unsecured debt which the
Company may incur.
 
RESTRICTIONS ON CONSOLIDATION, MERGER OR TRANSFER OF ASSETS
 
     The Company may not consolidate with or merge into another corporation, or
convey, transfer or lease its properties and assets substantially as an entirety
to another entity, unless the corporation formed by or surviving such
consolidation or merger (if other than the Company), or the entity which
acquires or leases such properties and assets, is a corporation organized under
the laws of the United States of America, any State thereof or the District of
Columbia and shall assume payment of the Unsecured Debt Securities and the
performance of all of the other covenants of the Company under the Indenture,
and immediately after giving effect to such transaction no default under the
Indenture shall have happened and be continuing. (See Section 5.01) Unless
otherwise indicated in the applicable Prospectus Supplement, the Indenture does
not contain covenants specifically designed to protect holders of Unsecured Debt
Securities in the event of a highly leveraged transaction.
 
MODIFICATION OF THE INDENTURE
 
     Certain modifications and amendments of the Indenture may be made by the
Company and the Trustee only with the consent of the holders of a majority in
aggregate principal amount of the outstanding Unsecured Debt Securities of each
series issued under the Indenture which is affected by the modification or
amendment, provided that no such modification or amendment may, without the
consent of the holder of each Unsecured Debt Security affected thereby:
 
     - change the stated maturity date of the principal of, or any installment
       of interest on, any such Unsecured Debt Security;
 
     - reduce the principal amount of, or interest (or premium, if any) on, any
       such Unsecured Debt Security;
 
     - change the currency of payment of principal of, or interest (or premium,
       if any) on, any such Unsecured Debt Security;
 
     - impair the right to institute suit for the enforcement of any payment of
       the principal of, and premium, if any, and interest on any such Unsecured
       Debt Security or adversely affect the right of repayment, if any, at the
       option of the holder; or
 
     - reduce the percentage of holders of each affected series of Unsecured
       Debt Securities necessary to modify or amend the Indenture or waive
       defaults with respect to the series.
 
(See Section 9.02)
 
                                       21
<PAGE>   23
 
EVENTS OF DEFAULT
 
     The Indenture defines an Event of Default with respect to any series of
Unsecured Debt Securities as being any one of the following events and such
other event as may be established for the Unsecured Debt Securities of a
particular series:
 
     - default for 30 days in the payment of any interest on such series;
 
     - default for 3 business days in any payment of principal, and premium, if
       any, on such series when due;
 
     - default for 60 days, after appropriate notice, in performance of any
       other agreement in the Indenture with respect to such series or in the
       Unsecured Debt Securities of such series; or
 
     - certain events in bankruptcy, insolvency or reorganization.
 
No Event of Default with respect to a particular series of Unsecured Debt
Securities issued under the Indenture (other than under the immediately
preceding bullet point) necessarily constitutes an Event of Default with respect
to any other series of Unsecured Debt Securities issued thereunder. In case an
Event of Default shall occur and be continuing with respect to any series of
Unsecured Debt Securities, the Trustee or the holders of not less than 33% in
aggregate principal amount of the Unsecured Debt Securities then outstanding of
the series may declare the principal of such series (or such portion of the
principal as may be specified as due upon acceleration at that time in the terms
of that series) to be due and payable. Any Event of Default with respect to a
particular series of Unsecured Debt Securities may be waived by the holders of a
majority in aggregate principal amount of the outstanding Unsecured Debt
Securities of such series, except in each case a failure to pay principal or
premium, if any, or any interest on such Unsecured Debt Security. (See Sections
6.01, 6.02 and 6.04)
 
     The Indenture requires the Company to file annually with the Trustee a
statement signed by two officers of the Company as to the absence of defaults
under the terms of the Indenture. The Indenture provides that the Trustee may
withhold notice to the holders of the Unsecured Debt Securities of any default
(except in payment of principal or premium, if any, or interest) if it considers
it in the interest of the holders of the Unsecured Debt Securities to do so.
(See Sections 4.04 and 7.05)
 
     Subject to the provisions of the Indenture relating to the duties of the
Trustee in case an Event of Default shall occur and be continuing, the Indenture
provides that the Trustee shall be under no obligation to exercise any of its
rights or powers under the Indenture at the request, order or direction of the
holders of the Unsecured Debt Securities unless such holders shall have offered
to the Trustee satisfactory indemnity. Subject to such provisions for
indemnification and certain other rights of the Trustee, the Indenture provides
that the holders of a majority in principal amount of the outstanding Unsecured
Debt Securities of any series affected shall have the right to direct the time,
method and place of conducting any proceeding for any remedy for that series
which is available to the Trustee or exercising any trust or power conferred on
the Trustee for the benefit of such series. (See Sections 6.05 and 7.01)
 
DEFEASANCE
 
     The Indenture provides that the Company may terminate its obligations under
the Indenture if (i) all the Unsecured Debt Securities either mature within one
year or are called for redemption within one year under arrangements
satisfactory to the Trustee for giving the notice of redemption and (ii) the
Company irrevocably deposits in trust with the Trustee money or U.S.
Governmental Obligations (as described below) sufficient to pay principal and
interest on the Unsecured Debt Securities to maturity or redemption, as the case
may be. (See Section 8.01) For this purpose, U.S. Government Obligations means
obligations issued or guaranteed by the United States of America the payment of
which the full faith and credit of the United States of America is pledged.
 
                                       22
<PAGE>   24
 
REGARDING THE TRUSTEE
 
     Harris Trust and Savings Bank is the Trustee under the Indenture. Harris
Trust and Savings Bank makes loans to the Company in the normal course of its
business.
 
                              PLAN OF DISTRIBUTION
 
     We may sell the Securities in the following ways:
 
     - through dealers;
 
     - through underwriters;
 
     - through agents;
 
     - directly to purchasers; or
 
     - through any combination of the above.
 
     The Prospectus Supplement will set forth the specific terms of the series
of Securities being offered (the "Offered Securities"), including:
 
     - the name or names of any underwriters,
 
     - the price to the public of the Offered Securities and the proceeds to the
       Company from such sale,
 
     - any underwriting discounts and other items constituting underwriters'
       compensation,
 
     - any initial public offering price, and
 
     - any discounts or concessions allowed or reallowed or paid to dealers.
 
Any initial public offering price and any discounts or concessions allowed or
reallowed or paid to dealers may be changed from time to time.
 
     If we use underwriters in the sale, the underwriters will acquire the
Securities for their own account and may resell the Securities from time to time
in one or more transactions, including negotiated transactions, at a fixed
public offering price or at varying prices determined at the time of sale. We
may offer the Securities to you either through underwriting syndicates
represented by one or more managing underwriters or directly by one or more
underwriters. We will name the underwriter or underwriters with respect to a
particular underwritten offering of Offered Securities in the Prospectus
Supplement relating to such offering and, if an underwriting syndicate is used,
we will also name the managing underwriter or underwriters on the cover page of
such Prospectus Supplement. Unless otherwise set forth in the Prospectus
Supplement, the obligations of the underwriters to purchase the Offered
Securities will be subject to certain conditions precedent, the underwriters
will be obligated to purchase all the Offered Securities if any are purchased,
and we will have agreed to indemnify the underwriters against certain civil
liabilities, including liabilities under the Securities Act.
 
     If we sell the Securities directly or through agents designated by us from
time to time, any agent involved in the offer or sale of the Offered Securities
in respect of which this Prospectus is delivered will be named, and any
commissions payable by us to such agent will be set forth, in the Prospectus
Supplement relating thereto. Unless otherwise indicated in the Prospectus
Supplement, any such agent will be acting on a reasonable best efforts basis for
the period of its appointment.
 
                                 LEGAL OPINIONS
 
     Certain legal matters in connection with the Securities will be passed upon
for the Company by Schiff Hardin & Waite, Chicago, Illinois and for any
underwriters, dealers or agents by counsel named in the applicable Prospectus
Supplement.
 
                                       23
<PAGE>   25
 
                                    EXPERTS
 
     The financial statements incorporated in this Prospectus by reference to
Illinois Power Company's Annual Report on Form 10-K for the year ended December
31, 1997, have been so incorporated in reliance on the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
said firm as experts in auditing and accounting.
 
                                       24
<PAGE>   26
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.
 
     The following table sets forth all expenses in connection with the
distribution of the Securities being registered. All amounts shown below are
estimates, except the registration fee:
 
<TABLE>
<S>                                                           <C>
Registration fee of Securities and Exchange Commission......  $ 69,500
Accountants' fees and expenses..............................    25,000
Legal fees and expenses.....................................    80,000
Rating agency fees..........................................    70,000
Trustee fees and expenses (including legal fees)............    60,000
Printing fees...............................................    30,000
Miscellaneous expenses......................................     5,500
                                                              --------
          Total.............................................  $340,000
                                                              ========
</TABLE>
 
ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
     Under Section 8.75 of the Illinois Business Corporation Act of 1983, the
Company is empowered, subject to the procedures and limitations stated therein,
to indemnify any person against expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by him in
connection with any threatened, pending or completed action, suit or proceeding
to which such person is made a party or threatened to be made a party by reason
of his being or having been a director, officer, employee or agent of the
Company, or serving or having served at the request of the Company as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise. Section 8.75 further provides that
indemnification pursuant to its provisions is not exclusive of other rights of
indemnification to which a person may be entitled under any by-law, agreement,
vote of stockholders or disinterested directors, or otherwise, and that such
indemnification shall continue as to a director, officer, employee or agent of
the Company who has ceased to serve in such capacity, and shall inure to the
benefit of the heirs, executors and administrators of such a person.
 
     The By-Laws of the Company provide, in substance, that the Company shall
indemnify any person against expenses (including attorney's fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by him in
connection with any threatened, pending or completed action, suit or proceeding,
whether civil, criminal, administrative or investigative, to which such person
is made a party or threatened to be made a party by reason of his being or
having been a director, officer, employee or agent of the Company, or serving or
having served at the request of the Company in one or more of the foregoing
capacities with another corporation, partnership, joint venture, trust or other
enterprise. The indemnification is not exclusive of other rights and shall
continue as to a person who has ceased to be a director, officer, employer or
agent and shall inure to the benefit of his heirs, executors and administrators.
 
     The Company presently has an insurance policy which, among other things,
includes liability insurance coverage for officers and directors under which
officers and directors are covered against any "loss" arising from any claim or
claims made against them by reason of any "wrongful act" in their respective
capacities of directors or officers. "Loss" is specifically defined to exclude
fines and penalties as well as matters deemed uninsurable under the law pursuant
to which the insurance policy shall be construed. The policy also contains other
specific exclusions, including illegally obtained personal profit or advantages,
and dishonesty. The policy also provides for reimbursement to the Company,
subject to certain deductibles, for loss incurred by having indemnified officers
or directors as authorized by state statute, the Company's By-laws or any other
agreement.
 
                                      II-1
<PAGE>   27
 
ITEM 16. LIST OF EXHIBITS.
 
     The Exhibits to this Registration Statement are listed in the Exhibit Index
located elsewhere herein.
 
ITEM 17. UNDERTAKINGS.
 
(a) The undersigned Registrant hereby undertakes:
 
     1. To file, during any period in which offers or sales are being made, a
        post-effective amendment to this Registration Statement:
 
          (i) To include any prospectus required by Section 10(a)(3) of the
              Securities Act of 1933;
 
         (ii) To reflect in the Prospectus any facts or events arising after the
              effective date of the Registration Statement (or the most recent
              post-effective amendment thereof) which individually or in the
              aggregate, represent a fundamental change in the information set
              forth in the Registration Statement. Notwithstanding the
              foregoing, any increase or decrease in volume of securities
              offered (if the total dollar value of securities offered would not
              exceed that which was registered) and any deviation from the low
              or high end of the estimated maximum offering range may be
              reflected in the form of prospectus filed with the Commission
              pursuant to Rule 424(b) if, in the aggregate, the changes in
              volume and price represent no more than a 20% change in the
              maximum aggregate offering price set forth in the "Calculation of
              Registration Fee" table in the effective Registration Statement;
 
        (iii) To include any material information with respect to the plan of
              distribution not previously disclosed in the Registration
              Statement or any material change to such information in the
              Registration Statement;
 
        provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply
        if the Registration Statement is on Form S-3, Form S-8 or Form F-3, and
        the information required to be included in a post-effective amendment by
        those paragraphs is contained in periodic reports filed by the
        Registrant pursuant to Section 13 or 15(d) of the Securities Exchange
        Act of 1934 that are incorporated by reference in this Registration
        Statement.
 
     2. That, for the purpose of determining any liability under the Securities
        Act of 1933, each such post-effective amendment shall be deemed to be a
        new registration statement relating to the securities offered therein,
        and the offering of such securities at that time shall be deemed to be
        the initial bona fide offering thereof; and
 
     3. To remove from registration by means of a post-effective amendment any
        of the securities being registered which remain unsold at the
        termination of the offering.
 
(b) The undersigned Registrant hereby undertakes that, for purposes of
    determining any liability under the Securities Act of 1933, each filing of
    the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of
    the Securities Exchange Act of 1934 (and, where applicable, each filing of
    an employee benefit plan's annual report pursuant to Section 15(d) of the
    Securities Exchange Act of 1934) that is incorporated by reference in the
    Registration Statement shall be deemed to be a new registration statement
    relating to the securities offered therein, and the offering of such
    securities at that time shall be deemed to be the initial bona fide offering
    thereof.
 
(c) Insofar as indemnification for liabilities arising under the Securities Act
    of 1933 may be permitted to directors, officers and controlling persons of
    the Registrant pursuant to the statutory and bylaw provisions referred to in
    Item 15, or otherwise, the Registrant has been informed that in the opinion
    of the Securities and Exchange Commission such indemnification is against
    public policy as expressed in the Securities Act of 1933 and is therefore,
    unenforceable. In the event that a claim for indemnification against such
    liabilities (other than the payment by the Registrant of expenses incurred
    or paid by a director, officer or controlling person of the Registrant in
    the successful defense of any action, suit or proceeding) is asserted by
    such director, officer or controlling person in connection with the
    securities being registered, the
                                      II-2
<PAGE>   28
 
    Registrant will, unless in the opinion of its counsel the matter has been
    settled by controlling precedent, submit to a court of appropriate
    jurisdiction the question whether such indemnification by it is against
    public policy as expressed in the Securities Act of 1933 and will be
    governed by the final adjudication of such issue.
 
(d) The undersigned Registrant hereby undertakes that:
 
     1. For purposes of determining any liability under the Securities Act of
        1933, the information omitted from the form of prospectus filed as part
        of this Registration Statement in reliance upon Rule 430A and contained
        in a form of prospectus filed by the Registrant pursuant to Rule
        424(b)(1) or (4) or 497(h) under the Securities Act of 1933 shall be
        deemed to be part of this Registration Statement as of the time it was
        declared effective; and
 
     2. For purposes of determining any liability under the Securities Act of
        1933, each post-effective amendment that contains a form of prospectus
        shall be deemed to be a new registration statement relating to the
        securities offered therein, and the offering of such securities at that
        time shall be deemed to be the initial bona fide offering thereof.
 
                                      II-3
<PAGE>   29
 
                                   SIGNATURES
 
     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, REGISTRANT
CERTIFIES THAT IT HAS REASONABLE GROUNDS TO BELIEVE THAT IT MEETS ALL OF THE
REQUIREMENTS FOR FILING ON FORM S-3 AND HAS DULY CAUSED THIS REGISTRATION
STATEMENT TO BE SIGNED ON ITS BEHALF BY THE UNDERSIGNED, THEREUNTO DULY
AUTHORIZED, IN THE CITY OF DECATUR, AND STATE OF ILLINOIS ON THE 22ND DAY OF
JANUARY, 1999.
 
                                            ILLINOIS POWER COMPANY
                                            (REGISTRANT)
 
                                            BY:  /S/ LARRY F. ALTENBAUMER
                                              ----------------------------------
                                                     LARRY F. ALTENBAUMER
                                                  SENIOR VICE PRESIDENT AND
                                                   CHIEF FINANCIAL OFFICER
 
                                      II-4
<PAGE>   30
 
                               POWER OF ATTORNEY
 
     KNOW ALL MEN BY THESE PRESENTS, that Illinois Power Company and each of the
undersigned officers and directors of Illinois Power Company hereby constitute
and appoint each of Charles E. Bayless, Larry F. Altenbaumer and Leah Manning
Stetzner the true and lawful attorney-in-fact and agent of the undersigned, with
full power of substitution and resubstitution for and in the name, place and
stead of the undersigned, in any and all capacities, to sign all or any
amendments (including post-effective amendments) of and supplements to this
Registration Statement on Form S-3 and to file the same, with all exhibits
thereto, and other documents in connection therewith, with the Securities and
Exchange Commission, granting unto each such attorney-in-fact and agent full
power and authority to do and perform each and every act and thing requisite and
necessary to be done in and about the premises, to all intents and purposes and
as fully as said corporation itself and each said officer or director might or
could do in person, hereby ratifying and confirming all that each such
attorney-in-fact and agent, or his or her substitutes, may lawfully do or cause
to be done by virtue hereof.
 
     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THIS
REGISTRATION STATEMENT HAS BEEN SIGNED BELOW BY THE FOLLOWING PERSONS IN THE
CAPACITIES AND ON THE DATES INDICATED.
 
<TABLE>
<CAPTION>
                      SIGNATURE                                   TITLE                     DATE
                      ---------                                   -----                     ----
<C>                                                    <S>                           <C>
               /s/ CHARLES E. BAYLESS                  Chairman, President, Chief     January 22, 1999
- -----------------------------------------------------  Executive Officer and
                 Charles E. Bayless                    Director
            (Principal Executive Officer)
 
              /s/ LARRY F. ALTENBAUMER                 Senior Vice President and      January 22, 1999
- -----------------------------------------------------  Chief Financial Officer
                Larry F. Altenbaumer
              (Principal Financial and
                 Accounting Officer)
 
                                                       Director
- -----------------------------------------------------
                   J. Joe Adorjan
 
               /s/ C. STEVEN MCMILLAN                  Director                       January 22, 1999
- -----------------------------------------------------
                 C. Steven McMillan
 
                /s/ ROBERT M. POWERS                   Director                       January 22, 1999
- -----------------------------------------------------
                  Robert M. Powers
 
               /s/ SHELI Z. ROSENBERG                  Director                       January 22, 1999
- -----------------------------------------------------
                 Sheli Z. Rosenberg
 
                 /s/ WALTER D. SCOTT                   Director                       January 22, 1999
- -----------------------------------------------------
                   Walter D. Scott
 
                 /s/ JOE J. STEWART                    Director                       January 22, 1999
- -----------------------------------------------------
                   Joe J. Stewart
</TABLE>
 
                                      II-5
<PAGE>   31
 
<TABLE>
<CAPTION>
                      SIGNATURE                                   TITLE                     DATE
                      ---------                                   -----                     ----
<C>                                                    <S>                           <C>
               /s/ RONALD L. THOMPSON                  Director                       January 22, 1999
- -----------------------------------------------------
                 Ronald L. Thompson
 
                /s/ WALTER M. VANNOY                   Director                       January 22, 1999
- -----------------------------------------------------
                  Walter M. Vannoy
 
                                                       Director
- -----------------------------------------------------
                 Marilou von Ferstel
 
                 /s/ JOHN D. ZEGLIS                    Director                       January 22, 1999
- -----------------------------------------------------
                   John D. Zeglis
</TABLE>
 
                                      II-6
<PAGE>   32
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
        EXHIBIT                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
          1.1            Form of Underwriting Agreement for New Mortgage Bonds.
          1.2            Form of Underwriting Agreement for Unsecured Debt
                         Securities.
          3.1            Amended and Restated Articles of Incorporation of the
                         Company. Filed as Exhibit 3(a) to the Current Report on Form
                         8-K dated September 7, 1994 (File No. 1-3004).+
          3.2            By-laws of the Company. Filed as Exhibit 3(b)(1) to the
                         Annual Report on Form 10-K for the year ended December 31,
                         1994 (File No. 1-3004).+
          4.1            Mortgage and Deed of Trust dated November 1, 1943. Filed as
                         Exhibit 2(b) Registration No. 2-14066.+
          4.2            Supplemental Indenture dated July 1, 1949. Filed as Exhibit
                         7(a) Registration No. 2-8130.+
          4.3            Supplemental Indenture dated May 1, 1974. Filed as Exhibit
                         2(v) Registration No. 2-51674.+
          4.4            Supplemental Indenture dated May 1, 1977. Filed as Exhibit
                         2(w) Registration No. 2-59465.+
          4.5            Supplemental Indenture dated July 1, 1979. Filed as Exhibit
                         2 to the Quarterly Report on Form 10-Q for the Quarter Ended
                         June 30, 1979. (File No. 1-3004).+
          4.6            Supplemental Indenture dated March 1, 1985. Filed as Exhibit
                         4(a) to the Quarterly Report on Form 10-Q for the Quarter
                         Ended March 31, 1985. (File No. 1-3004).+
          4.7            Indenture dated as of July 15, 1986. Filed as Exhibit 4(b)
                         to the Current Report on Form 8-K dated June 25, 1986. (File
                         No. 1-3004).+
          4.8            Supplemental Indenture dated July 1, 1987. Filed as Exhibit
                         4(ll) to the Annual Report on Form 10-K for the Year Ended
                         December 31, 1987. (File No. 1-3004).+
          4.9            Supplemental Indenture dated December 13, 1989, to Indenture
                         dated as of July 15, 1996. Filed as Exhibit 4(nn) to the
                         Annual Report on Form 10-K for the Year Ended December 31,
                         1989. (File No. 1-3004).+
          4.10           Supplemental Indenture dated July 1, 1991. Filed as Exhibit
                         4(mm) to the Annual Report on Form 10-K for the Year Ended
                         December 31, 1991. (File No. 1-3004).+
          4.11           Supplemental Indenture No. 1 dated June 1, 1992. Filed as
                         Exhibit 4(nn) to the Quarterly Report on Form 10-Q for the
                         Quarter Ended June 30, 1992. (File No. 1-3004).+
          4.12           Supplemental Indenture No. 2 dated June 1, 1992. Filed as
                         Exhibit 4(oo) to the Quarterly Report on Form 10-Q for the
                         Quarter Ended June 30, 1992. (File No. 1-3004).+
          4.13           Supplemental Indenture No. 1 dated July 1, 1992. Filed as
                         Exhibit 4(pp) to the Quarterly Report on Form 10-Q for the
                         Quarter Ended June 30, 1992. (File No. 1-3004).+
          4.14           Supplemental Indenture No. 2 dated July 1, 1992. Filed as
                         Exhibit 4(qq) to the Quarterly Report on Form 10-Q for the
                         Quarter Ended June 30, 1992. (File No. 1-3004).+
          4.15           Supplemental Indenture dated September 1, 1992. Filed as
                         Exhibit 4(rr) to the Quarterly Report on Form 10-Q for the
                         Quarter Ended September 30, 1992. (File No. 1-3004).+
</TABLE>
<PAGE>   33
 
<TABLE>
<CAPTION>
        EXHIBIT                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
          4.16           General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992. Filed as Exhibit 4(cc) to the Annual
                         Report on Form 10-K for the Year Ended December 31, 1992.
                         (File No. 1-3004).+
          4.17           Supplemental Indenture dated February 15, 1993, to Mortgage
                         and Deed of Trust dated November 1, 1943. Filed as Exhibit
                         4(dd) to the Annual Report on Form 10-K for the Year Ended
                         December 31, 1992. (File No. 1-3004).+
          4.18           Supplemental Indenture dated February 15, 1993, to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(ee) to the Annual Report on Form
                         10-K for the Year Ended December 31, 1992. (File No.
                         1-3004).+
          4.19           Supplemental Indenture No. 1 dated March 15, 1993, to
                         Mortgage and Deed of Trust dated November 1, 1943. Filed as
                         Exhibit 4(ff) to the Annual Report on Form 10-K for the Year
                         Ended December 31, 1992. (File No. 1-3004).+
          4.20           Supplemental Indenture No. 1 dated March 15, 1993, to
                         General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992. Filed as Exhibit 4(gg) to the Annual
                         Report on Form 10-K for the Year Ended December 31, 1992.
                         (File No. 1-3004).+
          4.21           Supplemental Indenture No. 2 dated March 15, 1993, to
                         Mortgage and Deed of Trust dated November 1, 1943. Filed as
                         Exhibit 4(hh) to the Annual Report on Form 10-K for the Year
                         Ended December 31, 1992. (File No. 1-3004).+
          4.22           Supplemental Indenture No. 2 dated March 15, 1993, General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(ii) to the Annual Report on Form
                         10-K for the Year Ended December 31, 1992. (File No.
                         1-3004).+
          4.23           Supplemental Indenture dated July 15, 1993 to Mortgage and
                         Deed of Trust dated November 1, 1943. Filed as Exhibit 4(jj)
                         to the Quarterly Report on Form 10-Q for the Quarter Ended
                         June 30, 1993. (File No. 1-3004).+
          4.24           Supplemental Indenture dated July 15, 1993 to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(kk) to the Quarterly Report on Form
                         10-Q for the Quarter Ended June 30, 1993. (File No.
                         1-3004).+
          4.25           Supplemental Indenture dated August 1, 1993 to Mortgage and
                         Deed of Trust dated November 1, 1943. Filed as Exhibit 4(11)
                         to the Quarterly Report on Form 10-Q for the Quarter Ended
                         June 30, 1993. (File No. 1-3004).+
          4.26           Supplemental Indenture dated August 1, 1993 to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(mm) to the Quarterly Report on Form
                         10-Q for the Quarter Ended June 30, 1993. (File No.
                         1-3004).+
          4.27           Supplemental Indenture dated October 15, 1993, to Mortgage
                         and Deed of Trust dated November 1, 1943. Filed as Exhibit
                         4(nn) to the Quarterly Report on Form 10-Q for the Quarter
                         ended September 30, 1993. (File No. 1-3004).+
          4.28           Supplemental Indenture dated October 15, 1993, to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(oo) to the Quarterly Report on Form
                         10-Q for the Quarter ended September 30, 1993. (File No.
                         1-3004).+
          4.29           Supplemental Indenture dated November 1, 1993, to Mortgage
                         and Deed of Trust dated November 1, 1943. Filed as Exhibit
                         4(pp) to the Quarterly Report on Form 10-Q for the Quarter
                         ended September 30, 1993. (File No. 1-3004).+
          4.30           Supplemental Indenture dated November 1, 1993, to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(qq) to the Quarterly Report on Form
                         10-Q for the Quarter ended September 30, 1993. (File No.
                         1-3004).+
          4.31           Supplemental Indenture dated February 1, 1994, to Mortgage
                         and Deed of Trust dated November 1, 1943. Filed as Exhibit
                         4(hh) to the Annual Report on Form 10-K for the Year ended
                         December 31, 1993. (File No. 1-3004).+
</TABLE>
<PAGE>   34
 
<TABLE>
<CAPTION>
        EXHIBIT                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
          4.32           Indenture dated as of October 1, 1994 between Illinois Power
                         Company and The First National Bank of Chicago. Filed as
                         Exhibit 4(a) to the Quarterly Report on Form 10-Q for the
                         Quarter ended September 30, 1994. (File No. 1-3004).+
          4.33           First Supplemental Indenture dated as of October 1, 1994, to
                         Indenture dated as of October 1, 1994. Filed as Exhibit 4(b)
                         to the Quarterly Report on Form 10-Q for the Quarter ended
                         September 30, 1994. (File No. 1-3004).+
          4.34           Indenture dated as of January 1, 1996 between Illinois Power
                         Company and Wilmington Trust Company. Filed as Exhibit
                         4(b)(36) to the Annual Report on Form 10-K for the Year
                         ended December 31, 1995. (File No. 1-3004).+
          4.35           First Supplemental Indenture dated as of January 1, 1996, to
                         Indenture dated January 1, 1996. Filed as Exhibit 4(b)(37)
                         to the Annual Report on Form 10-K for the Year ended
                         December 31, 1995. (File No. 1-3004).+
          4.36           Supplemental Indenture dated April 1, 1997, to Mortgage and
                         Deed of Trust dated November 1, 1943. Filed as Exhibit 4(a)
                         to the Quarterly Report on Form 10-Q for the Quarter ended
                         March 31, 1997. (File No. 1-3004).+
          4.37           Supplemental Indenture dated April 1, 1997 to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992. Filed as Exhibit 4(b) to the Quarterly Report on Form
                         10-Q for the Quarter ended March 31, 1997. (File No.
                         1-3004).+
          4.38           Supplemental Indenture dated December 1, 1997 to Mortgage
                         and Deed of Trust dated November 1, 1943. Filed as Exhibit
                         4(b)(36) to the Annual Report on Form 10-K for the Year
                         Ended December 31, 1997. (File No. 1-3004).+
          4.39           Supplemental Indenture No. 1 dated as of March 1, 1998 to
                         Mortgage and Deed of Trust dated November 1, 1943.
          4.40           Supplemental Indenture No. 2 dated as of March 1, 1998 to
                         Mortgage and Deed of Trust dated November 1, 1943.
          4.41           Supplemental Indenture No. 1 dated as of March 1, 1998 to
                         General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992.
          4.42           Supplemental Indenture No. 2 dated as of March 1, 1998 to
                         General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992.
          4.43           Supplemental Indenture dated as of July 15, 1998 to Mortgage
                         and Deed of Trust dated November 1, 1943.
          4.44           Supplemental Indenture dated as of July 15, 1998 to General
                         Mortgage Indenture and Deed of Trust dated as of November 1,
                         1992.
          4.45           Supplemental Indenture dated as of September 15, 1998 to
                         Mortgage and Deed of Trust dated November 1, 1943.
          4.46           Supplemental Indenture dated as of September 15, 1998 to
                         General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992.
          4.47           Supplemental Indenture dated as of October 1, 1998 to
                         General Mortgage Indenture and Deed of Trust dated as of
                         November 1, 1992.
          4.48           Form of Supplemental Indenture for New Mortgage Bonds.
          4.49           Specimen New Mortgage Bond-included in Exhibit 4.48.
          4.50           Form of Unsecured Note.
          4.51           Form of Unsecured Debenture.
          5              Opinion of Schiff Hardin & Waite.
         12              Statement of Computation of Ratio of Earnings to Fixed
                         Charges.
         23.1            Consent of PricewaterhouseCoopers LLP.
</TABLE>
<PAGE>   35
 
<TABLE>
<CAPTION>
        EXHIBIT                                  DESCRIPTION
        -------                                  -----------
<C>                      <S>
         23.2            Consent of Schiff Hardin & Waite (contained in its opinion
                         filed as Exhibit 5 to the Registration Statement).
         25              Powers of Attorney (set forth on the signature pages of the
                         Registration Statement).
         26.1            Form T-1 Statement of Eligibility under the Trust Indenture
                         Act of 1939 of Harris Trust and Savings Bank with respect to
                         New Mortgage Bonds.
         26.2            Form T-1 Statement of Eligibility under the Trust Indenture
                         Act of 1939 of The Chase Manhattan Bank with respect to
                         Unsecured Debt Securities.
</TABLE>
 
- ---------------
 
+ Incorporated herein by reference.

<PAGE>   1
                                                                     EXHIBIT 1.1

                                                               ___________, ____
                                                               CHICAGO, ILLINOIS

                             ILLINOIS POWER COMPANY

                               NEW MORTGAGE BONDS

                             UNDERWRITING AGREEMENT

To the Representative(s) named in Schedule I
hereto of the Underwriters named in Schedule II hereto.

Ladies and Gentlemen:

     Illinois Power Company, an Illinois corporation (the "Company"), proposes
to issue and sell from time to time, in one or more series, its New Mortgage
Bonds which are registered under the registration statement referred to in
Section 1(a) ("Bonds"). The Bonds will be issued under the Company's General
Mortgage and Deed of Trust, dated as of November 1, 1992 (the "General
Mortgage"), and supplemental indentures thereto, including a supplemental
indenture (the "Supplemental Indenture") specifically relating to the Purchased
Bonds (as defined below), between the Company and the Harris Trust and Savings
Bank, as trustee (the "New Mortgage Trustee") (the General Mortgage and all
supplemental indentures thereto are collectively referred to as the "New
Mortgage"). The Bonds will be secured primarily by a bond issued to the New
Mortgage Trustee under the Company's Mortgage and Deed of Trust dated November
1, 1943 from the Company to Harris Trust and Savings Bank, as trustee (the
"First Mortgage Trustee") as amended and supplemented by various supplemental
indentures (the "First Mortgage"), including a supplemental indenture (the
"First Mortgage Supplemental Indenture") specifically relating to the bond (the
"First Mortgage Bond") securing the Purchase Bonds (as hereinafter deferred).
The Company proposes to sell to the underwriters named in Schedule II hereto
(the "Underwriters") for whom you are acting as Representative or
Representatives (the "Representatives"), Bonds in the aggregate principal
amount and of the series identified in Schedule I hereto (the "Purchased
Bonds").

     1.   Representations and Warranties of the Company. The Company represents
and warrants to, and agrees with the Underwriters that:

          (a)  A registration statement on Form S-3 (No. 333-       ) relating
to the Bonds has been filed with the Securities and Exchange Commission (the
"Commission") under the Securities Act of 1933, as amended (the "Act") and has
become effective. Such registration statement, including the prospectus
contained therein, as amended and supplemented to the date of this Agreement
(exclusive of supplements to the prospectus relating solely to Bonds that are
not the Purchased Bonds) and as supplemented by the 
<PAGE>   2
     prospectus supplement to be included as part of the prospectus to be filed
     with the Commission pursuant to Rule 424(b) under the Act, as provided in
     Section 3(a) hereof, are collectively referred to as the "Registration
     Statement" and such prospectus is collectively referred to as the
     "Prospectus." Any reference herein to the Registration Statement or the
     Prospectus shall be deemed to include the documents incorporated by
     reference therein pursuant to Item 12 of Form S-3 which were filed under
     the Securities Exchange Act of 1934, as amended (the "Exchange Act") on or
     before the date of this Agreement; and any reference herein to the terms
     "amend," "amendment" or "supplement" with respect to the Registration
     Statement or the Prospectus shall be deemed to refer to and include
     the filing of any document under the Exchange Act deemed to be incorporated
     therein by reference after the date of this Agreement.

          (b)  The Registration Statement and the Prospectus, both at the time
     the Prospectus is filed with the Commission pursuant to Rule 424(b) under
     the Act as provided in Section 3(a) hereof, and any further amendments and
     supplements to the Prospectus when they become effective or are filed with
     the Commission, as the case may be, prior to the Closing Date (as defined
     below), will conform in all respects to the requirements of the Act, the
     Exchange Act, the Trust Indenture Act of 1939, as amended (the "Trust
     Indenture Act") and the rules and regulations of the Commission (the "Rules
     and Regulations"), and none of such documents will include any untrue
     statement of a material fact or omit to state any material fact required to
     be stated therein or necessary to make the statements therein, in light of
     the circumstances under which they were made, not misleading, except that
     the foregoing does not apply to statements or omissions in such documents
     based upon written information furnished to the Company by any Underwriter
     specifically for use therein or in reliance upon and in conformity with the
     Form T-1 of the New Mortgage Trustee.

     2.   Purchase, Offering and Delivery. Subject to the terms and conditions
herein set forth, the Company agrees to sell to each Underwriter, and each
Underwriter agrees, severally and not jointly, to purchase from the Company, at
the purchase price set forth in Schedule I hereto, the principal amount of the
Purchased Bonds set forth opposite such Underwriter's name in Schedule II
hereto. It is understood that the Underwriters propose to offer the Purchased
Bonds for sale to the public as set forth in the prospectus supplement relating
to the Purchased Bonds.

     The Purchased Bonds to be purchased by each Underwriter shall be delivered
by the Company for the account of such Underwriter to the place specified in
Schedule I hereto against payment of the purchase price therefor by such
Underwriter or on its behalf in the type of funds and method of payment
specified in Schedule I hereto, drawn to the order of the Company, at the
office of Harris Trust and Savings Bank, 111 West Monroe Street, Chicago,
Illinois 60690, at the time and date specified in Schedule I hereto or at such
other time and date as the Representatives and the Company may agree, such time
and date being herein referred to as the "Closing Date." The Purchased Bonds so
to be delivered will be in definitive fully registered form in such authorized
denominations and registered in such names as the Representatives request at
least two full business





                                       2


<PAGE>   3
days before the Closing Date and will be made available for checking and
packaging in the City designated in Schedule I as the place of delivery at
least 24 hours prior to the Closing Date.

     3.   Covenants of the Company. The Company covenants and agrees with the
Underwriters that:

          (a)  Promptly following execution of this Agreement, the Company will
     cause the Prospectus (including as part thereof a prospectus supplement
     relating to the Purchased Bonds (the "Prospectus Supplement")) to be filed
     with the Commission pursuant to Rule 424(b) under the Act and the Company
     will promptly advise the Representatives when such filing has been made.
     Prior to such filing, the Company will work with the Representatives in the
     preparation of the Prospectus Supplement to assure that the Representatives
     have no reasonable objection to the form or content thereof when filed.

          (b)  If at any time when a prospectus relating to the Purchased Bond
     is required to be delivered under the Act any event occurs as a result of
     which the Prospectus as then amended or supplemented would include an
     untrue statement of a material fact, or omit to state any material fact
     required to be stated therein or necessary to make the statements therein,
     in the light of the circumstances under which they were made, not
     misleading, or if it is necessary at any time to amend or supplement the
     Registration Statement or Prospectus to comply with the Act or the Rules or
     Regulations, the Company promptly will prepare and file with the Commission
     an amendment or supplement which will correct such statement or omission,
     or an amendment which will effect such compliance.

          (c)  The Company will furnish to each Underwriter such number of
     copies of the Prospectus as may be reasonably requested in connection with
     the offering of the Purchased Bonds.

          (d)  The Company will pay all expenses incident to the performance of
     its obligations under this Agreement, and will reimburse the Underwriters
     for any expenses up to $__________ in the aggregate (including fees and
     disbursements of counsel) incurred in connection with qualification of the
     Purchased Bonds for sale and determination of their eligibility for
     investment under the laws of such jurisdictions as the Representatives
     designate and the printing of memoranda relating thereto.

          (e)  The Company will not, for the period ending on the day
     immediately succeeding the Closing Date, without the prior written consent
     of the Underwriters, offer, sell or contract to sell, or otherwise dispose
     of, directly or indirectly, or announce the offering of, any other debt
     securities of the Company.

     4.   Conditions to the Obligations of the Underwriters. The obligation of
the several Underwriters to purchase and pay for the Purchased Bonds hereunder
will be subject to the accuracy


                                       3
<PAGE>   4
of the representations and warranties on the part of the Company herein, to the
performance by the Company of its obligations hereunder and to the following
additional conditions precedent:

          (a)  Subsequent to the execution and delivery of this Agreement there
     shall not have occurred (i) any change, or any development involving a
     prospective change, in or affecting particularly the business or properties
     of the Company or its subsidiaries which, in the judgment of a majority in
     interest of the Underwriters, including you, materially impairs the
     investment quality of the Purchased Bonds or (ii) any downgrading in the
     rating of the Company's debt securities by any "nationally recognized
     statistical rating organization" (as defined for purposes of Rule 436(g)
     under the Act).

          (b)  No stop order suspending the effectiveness of the Registration
     Statement shall have been issued and no proceedings for that purpose shall
     have been instituted or, to the knowledge of the Company, or the
     Underwriters, shall be contemplated by the Commission.

          (c)  The Underwriters shall have received the following:

               (i)  A letter of Price Waterhouse, dated the Closing Date,
confirming that they are independent accountants within the meaning of the Act
and the Rules and Regulations, and stating in effect that (i) in their opinion,
the financial statements examined by them and incorporated by reference in the
Prospectus comply as to form in all material respects with the accounting
requirements of the Act and the Rules and Regulations applicable to annual
reports on Form 10-K (ii) on the basis of a reading of the interim financial
statements referred to in Clause (A) below, a reading of the latest available
interim financial statements of the Company, a reading of the minutes of the
Board of Directors and stockholders of the Company as set forth in the minute
books of the Company and inquiries of officials of the Company responsible for
financial and accounting matters, nothing came to their attention that caused
them to believe that (A) the unaudited financial statements included in the most
recent Quarterly Report on Form 10-Q incorporated by reference in the Prospectus
were not prepared on a basis substantially consistent with that of the audited
financial statements as of and for the fiscal year ended December 31, 199__
incorporated by reference in the Prospectus, or (B) at the date of the latest
available balance sheet read by such accountants or at a subsequent specified
date not more than five days prior to the Closing Date, there was any change in
the capital stock or long-term debt of the Company or, at the date of the latest
available balance sheet read by such accountants, there was any decrease in net
assets, in each case as compared with the corresponding amounts shown in the
December 31, 199__ balance sheet incorporated by reference in the Prospectus, or
(C) for the period of twelve months ended with the Closing Date or of the latest
available income statement read by such accountants, there were any decreases,
as compared with the twelve months ended December 31, 199__ in operating
revenues, operating income, net income, earnings per share of common stock or
the ratio of earnings to fixed charges, except in all cases set forth


                                       4
<PAGE>   5
          in clauses (B) and (C) above for changes or decreases which the
          Prospectus discloses have occurred or may occur, or which are
          described in such letter, and (iii) they have compared the dollar
          amounts (or percentages derived from such dollar amounts) and other
          financial information contained in the Prospectus under the captions
          "Use of Proceeds," "Ratio of Earnings to Fixed Charges," and
          "Description of First Mortgage Bonds" and contained in the Company's
          Annual Report on Form 10-K for the year ended December 31, 199__ and
          Quarterly Report on Form 10-Q for the quarter ended __________, ______
          (which are incorporated by reference in the Prospectus) (in each case
          to the extent that such dollar amounts, percentages and other
          financial information are derived from the general accounting records
          of the Company subject to the internal controls of the Company's
          accounting system or are derived directly from such records by
          analysis or computation) with the results obtained from inquiries, a
          reading of such general accounting records and other procedures
          specified in such letter, and have found such dollar amounts,
          percentages and other financial information to be in agreement with
          such results except as otherwise specified in such letter. All
          financial statements included in material incorporated by reference in
          the Prospectus shall be deemed included in the Prospectus for purposes
          of this subsection.

               (ii) An opinion of Schiff Hardin & Waite, counsel for the
          Company, dated the Closing Date, to the effect that:

                    (A)  The Company has been duly incorporated and is validly
               existing as a corporation in good standing under the laws of the
               State of Illinois, with corporate power and authority to own its
               properties and conduct its business as described in the
               Prospectus, and the Company is not required to be qualified as a
               foreign corporation in any jurisdiction.

                    (B)  The Purchased Bonds have been duly authorized,
               executed, authenticated, issued and delivered, and constitute the
               valid and binding obligations of the Company enforceable in
               accordance with their terms, except as the same may be limited by
               (a) bankruptcy, insolvency, reorganization, moratorium or other
               laws relating to or affecting the enforcement of creditors'
               rights, and (b) general equitable principles (regardless of
               whether such enforceability is considered in a proceeding in
               equity or at law), and (subject to the qualifications mentioned
               in subparagraph C below with respect to the enforceability of the
               General Mortgage and to the provisions of any purchase or sinking
               fund or analogous provisions for any particular series of bonds
               established by any indenture supplemental to the General
               Mortgage) are entitled to the benefit and security of the General
               Mortgage in accordance with the terms thereof equally and ratably
               with all other bonds issued under the General Mortgage.


                                       5
<PAGE>   6
        (C) The General Mortgage and the Supplemental Indenture have each been
duly authorized, executed and delivered and are valid and binding instruments
enforceable in accordance with their terms, except as the same may be limited
by (a) bankruptcy, insolvency, reorganization, moratorium or other laws
relating to or affecting the enforcement of creditors' rights or the
enforcement of the security provided by the General Mortgage, and (b) general
equitable principles (regardless of whether such enforceability is considered
in a proceeding in equity or at law), and except that no opinion is expressed
with respect to the enforceability of the lien of the General Mortgage on
chattels as against third parties (other than chattels delivered in pledge to
the New Mortgage Trustee) or with respect to the enforceability of the lien of
the New Mortgage on after-acquired property (in respect of which a supplemental
indenture shall not have been executed, delivered and recorded) as against
purchasers for value and without notice. The laws of the State of Illinois
provide that no real estate in the State of Illinois shall be sold by virtue of
any power of sale contained in any mortgage, but that all such mortgages shall
be foreclosed only in the manner provided for foreclosing mortgages containing
no power of sale, and that no real estate shall be sold to satisfy any mortgage
except as authorized under the Illinois Mortgage Foreclosure Law. Such laws,
however, provide for the foreclosing of mortgages by judicial proceedings and,
in the judgment of such counsel, provide adequate remedies for the realization
of the benefits of the security provided in the General Mortgage.

        (D) The First Mortgage Bond has been duly authorized, executed,
authenticated, issued and delivered to the New Mortgage Trustee, and
constitutes the valid and binding obligation of the Company enforceable in
accordance with its terms, except as the same may be limited by (a) bankruptcy,
insolvency, reorganization moratorium or other laws relating to or affecting
the enforcement of creditors' rights, and (b) general equitable principles
(regardless of whether such enforceability is considered in a proceeding in
equity or at law), and (subject to the qualifications mentioned in subparagraph
(E) below with respect to the enforceability of the First Mortgage and to the
provisions of any purchase or sinking fund or analogous provisions for any
particular series of bonds established by any indenture supplemental to the
First Mortgage) is entitled to the benefit and security of the First Mortgage
in accordance with the terms thereof equally and ratably with all other bonds
issued under the First Mortgage; and the New Mortgage Trustee as the registered
owner of the First Mortgage Bond will be entitled to the payment of principal
and interest, and premium, if any, in case of redemption, as therein provided.

                                       6
<PAGE>   7
     (E)  The First Mortgage and the First Mortgage Supplemental Indenture have
each been duly authorized, executed and delivered and are valid and binding
instruments enforceable in accordance with their terms, except as the same may
be limited by (a) bankruptcy, insolvency, reorganization, moratorium or other
laws relating to or affecting the enforcement of creditors' rights or the
enforcement of the security provided by the First Mortgage, and (b) general
equitable principles (regardless of whether such enforceability is considered
in a proceeding in equity or at law), and except that no opinion is expressed
with respect to the enforceability of the lien of the First Mortgage on
chattels as against third parties (other than chattels delivered in pledge to
the First Mortgage Trustee), or with respect to the enforceability of the lien
of the First Mortgage on after-acquired property (in respect of which a
supplemental indenture shall not have been executed, delivered and recorded) as
against purchasers for value and without notice. The laws of the State of
Illinois provide that no real estate in the State of Illinois shall be sold by
virtue of any power of sale contained in any mortgage, but that all such
mortgages shall be foreclosed only in the manner provided for foreclosing
mortgages containing no power of sale, and that no real estate shall be sold to
satisfy any mortgage except as authorized under the Illinois Mortgage
Foreclosure Law. Such laws, however, provide for the foreclosing of mortgages
by judicial proceedings and, in our judgment, provide adequate remedies for the
realization of the benefits of the security provided in the First Mortgage.

     (F)  The General Mortgage constitutes a valid and legally effective
mortgage creating a valid lien, which lien is junior to the lien of the First
Mortgage, for the security of all bonds duly issued thereunder upon
substantially all of the Company's properties used in the generation, purchase,
transmission, distribution and sale of electricity or gas, with the exceptions,
and subject to the reservations, encumbrances (including the lien of the First
Mortgage) and restrictions recited in the granting and habendum clauses of, and
as provided in, the General Mortgage, or referred to in the Prospectus under
the subcaption "Security" under the caption "Description of the New Mortgage
Bonds." Except as to after-acquired property, and except as to property sold,
or under contract to be sold, or otherwise disposed of by the Company and
released from the lien of the General Mortgage, or abandoned, pursuant to the
provisions thereof, the Company has good and sufficient title to all the
properties described in, and conveyed or pledged by, the General Mortgage with
the exceptions and subject to the reservations, encumbrances (including the
lien of the First Mortgage) and restrictions recited in the granting and
habendum clauses of, and as provided in, the General Mortgage, or referred to
in the Prospectus under said sub-caption "Security."

                                       7
<PAGE>   8
     (G) The First Mortgage constitutes a valid and legally effective mortgage
creating a valid first lien for the security of all bonds duly issued thereunder
upon substantially all of the fixed properties owned and franchises and rights
held by the Company, with the exceptions, and subject to the reservations,
encumbrances and restrictions recited in the granting and habendum clauses of,
and as provided in, the First Mortgage, or referred to in the Prospectus under
the subcaption "Description of First Mortgage Bonds -- Security." Except as to
after-acquired property, and except as to property sold, or under contract to be
sold, or otherwise disposed of by the Company and released from the lien of the
First Mortgage, or abandoned, pursuant to the provisions thereof, the Company
has good and sufficient title to all the properties described in, and conveyed
or pledged by, the First Mortgage with the exceptions, and subject to the
reservations, encumbrances, and restrictions recited in the granting and
habendum clauses of, and as provided in, the First Mortgage, or referred to in
the Prospectus under said subcaption "Security."

     (H) The Registration Statement has become effective under the Act; the
General Mortgage has been duly qualified under the Trust Indenture Act to the
extent required; to the best of such counsel's knowledge, no stop order
suspending the effectiveness of the Registration Statement has been issued and
no proceedings for that purpose have been instituted or are pending or
contemplated under the Act, and the Registration Statement and the Prospectus,
and each amendment or supplement thereto, as of their respective effective or
issue dates, complied as to form in all material respects with the requirements
of the Act, the Exchange Act, the Trust Indenture Act and the Rules and
Regulations; such counsel has no reason to believe that the Registration
Statement or the Prospectus, or any such amendment or supplement, as of such
respective dates, contained any untrue statement of a material fact or omitted
to state any material fact required to be stated therein or necessary to make
the statements therein not misleading; the descriptions in the Registration
Statement and Prospectus of statutes, legal and governmental proceedings and
contracts and other documents are accurate and fairly present the information
required to be shown; and such counsel does not know of any legal or
governmental proceedings required to be described in the Prospectus which are
not described as required, nor of any contracts or documents of a character
required to be described in the Registration Statement or Prospectus or to be
filed as exhibits to the Registration Statement which are not described
and filed as required; it being understood that such counsel need express no
opinion as to the financial statements or other financial data contained in the
Registration Statement or the Prospectus.


                                       8
<PAGE>   9
    (I)  This Agreement has been duly authorized, executed and delivered by the
Company.

    (J)  The Illinois Commerce Commission has entered orders (a) permitting the
execution and delivery of the General Mortgage, the Supplemental Indenture, the
First Mortgage, and the First Mortgage Supplemental Indenture, respectively,
and (b) approving the issuance and sale of the Purchased Bonds and the issuance
and pledge of the First Mortgage Bond; said, orders are valid and in effect and
no further approval, authorization, consent or order of, or action by, any
other regulatory authority is necessary with respect to the execution and
delivery of the General Mortgage, the Supplemental Indenture, the First
Mortgage or the First Mortgage Supplemental Indenture, the issuance and
sale of the Purchased Bonds, or the issuance and pledge of the First Mortgage
Bond, each as contemplated by this Agreement; it being understood that in
giving such opinion such counsel is not passing upon the authorizations or
approvals which may be necessary under the securities or blue sky laws of any
jurisdiction other than the United States of America. The issuance and sale of
the Purchased Bonds and the issuance and pledge of the First Mortgage Bond,
each as contemplated by this Agreement, are in conformity with the terms of
said orders of the Illinois Commerce Commission.

    (K)  The statements made in the Prospectus under the caption "Description of
the New Mortgage Bonds" and the subcaption "Description of First Mortgage
Bonds," insofar as they purport to summarize provisions of the documents
specifically referred to under said captions, fairly present the information
called for with respect thereto by Form S-3.

    (L)  The statements in the Prospectus and in the Company's Annual Report on
Form 10-K for the year ended December 31, 199_ (which is incorporated by
reference in the Prospectus) as to matters of law and legal conclusions which
are stated in the Prospectus to have been made on the authority of such counsel,
have been reviewed by such counsel and, as to matters of law and legal
conclusions, are correct.

    (M)  The execution, delivery and performance by the Company of this
Agreement, the General Mortgage, the Supplemental Indenture and the First
Mortgage Supplemental Indenture, and the incurrence by the Company of the
obligations and the consummation of the transactions contemplated by this
Agreement and the foregoing Supplemental Indenture and First Mortgage
Supplemental Indenture, will not conflict with or constitute a breach of, or
default under, the Restated Articles of Incorporation or By-Laws of the Company
or, to such counsel's knowledge, any mortgage, contract, lease,

                                       9
<PAGE>   10
          note or other instrument to which the Company or any significant
          subsidiary of the Company is a party or by which the Company or any
          significant subsidiary of the Company may be bound, or any law,
          administrative regulation or any administrative, arbitration or court
          order.

          (iii) An opinion from __________________, counsel for the
     Underwriters, as to those matters as the Underwriters may reasonably
     require.

          (iv) A certificate of the Chairman, President, an Executive Vice
     President, a Senior Vice President, a Vice President or General Counsel and
     the Treasurer or the principal financial or accounting officer of the
     Company, dated the Closing Date, in which such officers, to the best of
     their knowledge after reasonable investigation, shall state that the
     representations and warranties of the Company in this Agreement are true
     and correct, that the Company has complied with all agreements and
     satisfied all conditions on its part to be performed or satisfied at or
     prior to the Closing Date, that no stop order suspending the effectiveness
     of the Registration Statement has been issued and no proceedings for that
     purpose have been instituted or are contemplated by the Commission, and
     that, subsequent to the date of the most recent financial statements in the
     Prospectus, there has been no material adverse change in the financial
     position or results of operations of the Company except as set forth or
     contemplated in the Prospectus or as described in such certificate.

          (v) An order or orders of the Illinois Commerce Commission authorizing
     the issuance and sale of the Purchased Bonds in accordance with the terms
     and conditions hereof shall be in full force and effect and shall contain
     no condition or provision unacceptable to the Underwriters, it being
     understood that no order in effect as of the date hereof contains any such
     unacceptable condition or provision.

          (vi) A copy of the Company's audited financial statements at December
     31, 199_, manually signed by Price Waterhouse.

The Company will furnish the Underwriters with such conformed copies of such
opinions, certificates, letters and documents as the Underwriters reasonably
request.

     5.  Conditions to the Obligation of the Company. The obligation of the
Company to sell and deliver the Purchased Bonds on the Closing Date is subject
to the following conditions precedent:

          (a)  Prior to the Closing Date, no stop order suspending the
     effectiveness of the Registration Statement shall have been issued and no
     proceedings for that purpose shall have been instituted, or, to the
     knowledge of the Company or the Underwriters, shall be contemplated by the
     Commission.


                                       10
<PAGE>   11
          (b)  There shall be in effect on the Closing Date an order of the
     Illinois Commerce Commission authorizing the issuance and sale of the
     Purchased Bonds in accordance with the terms and conditions thereof, and no
     order of the Illinois Commerce Commission shall be in effect at the Closing
     Date, which would prevent the sale and delivery of the Purchased Bonds or
     which contains any condition or provision with respect to such sale which
     is not acceptable to the Company, it being understood that no order in
     effect at the date of this Agreement contains any such unacceptable
     condition or provision.

If any such condition shall not have been satisfied, then the Company shall be
entitled, by notice in writing to the Underwriters, to terminate this Agreement
without liability on the part of the Company or any Underwriter, except as
provided herein.

     6.  Indemnification.

          (a) The Company will indemnify and hold harmless each Underwriter and
     each person, if any, who controls any Underwriter within the meaning of the
     Act against any losses, claims, damages or liabilities, joint or several,
     to which such Underwriter or such controlling person may become subject,
     under the Act or otherwise, insofar as such losses, claims, damages or
     liabilities (or actions in respect thereof) arise out of or are based upon
     any untrue statement or alleged untrue statement of any material fact
     contained in the Registration Statement, the Prospectus, or any amendment
     or supplement thereto, or arise out of or are based upon the omission or
     alleged omission to state therein a material fact required to be stated
     therein or necessary to make the statements therein not misleading; and
     will reimburse each Underwriter and each such controlling person for any
     legal or other expenses reasonably incurred by such Underwriter or such
     controlling person in connection with investigating or defending any such
     loss, claim, damage, liability or action; provided, however, that the
     Company will not be liable in any such case to the extent that any such
     loss, claim, damage or liability arises out of or is based upon an untrue
     statement or alleged untrue statement or omission or alleged omission made
     in any of such documents in reliance upon and in conformity with written
     information furnished to the Company by any Underwriter specifically for
     use therein or in reliance upon and in conformity with the Form T-1 of the
     New Mortgage Trustee. This indemnity agreement will be in addition to any
     liability which the Company may otherwise have.

          (b) Each Underwriter will indemnify and hold harmless the Company,
     each of its directors and officers and each person, if any, who controls
     the Company within the meaning of the Act, against any losses, claims,
     damages or liabilities to which the Company or any such director, officer
     or controlling person may become subject, under the Act or otherwise,
     insofar as such losses, claims, damages or liabilities (or actions in
     respect thereof) arise out of or are based upon any untrue statement or
     alleged untrue statement of any material fact contained in the Registration
     Statement, the Prospectus or any amendment or supplement thereto, or arise
     out of or are based upon the omission or the alleged omission to state
     therein a material fact required to be stated therein or necessary to make
     the

                                       11
<PAGE>   12
statements therein not misleading, in each case to the extent, but only to the
extent, that such untrue statement or alleged untrue statement or omission was
made in reliance upon and in conformity with written information furnished to
the Company by such Underwriters specifically for use therein; and will
reimburse any legal or other expenses reasonably incurred by the Company or
any such director, officer or controlling person in connection with
investigating or defending any such loss, claim, damage, liability or action.
This indemnity agreement will be in addition to any liability which such
Underwriters may otherwise have.

     (c)  Promptly after receipt by an indemnified party under this Section of
notice of the commencement of any action, such indemnified party will, if a
claim in respect thereof is to be made against the indemnifying party under this
Section, notify the indemnifying party of the commencement thereof; but the
omission so to notify the indemnifying party will not relieve it from any
liability which it may have to any indemnified party otherwise than under this
Section. In case any such action is brought against any indemnified party, and
it notifies the indemnifying party of the commencement thereof, the indemnifying
party will be entitled to participate therein and, to the extent that it may
wish, jointly with any other indemnifying party similarly notified, to assume
the defense thereof, with counsel satisfactory to such indemnified party (who
shall not, except with the consent of the indemnified party, be counsel to the
indemnifying party), and after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof, the
indemnifying party will not be liable to such indemnified party under this
Section for any legal or other expenses subsequently incurred by such
indemnified party in connection with the defense thereof other than reasonable
costs of investigation, except as otherwise provided in the succeeding sentence.
If the indemnifying party shall not have employed counsel to have charge of
the defense of any such action, or if any such indemnified party or parties
shall have reasonably concluded that there is a conflict of interest which may
give rise to defenses available to them which are different from or additional
to those available to the indemnifying party (in which case the indemnifying
party shall not have the right to direct the defense of such action on behalf of
the indemnified party or parties), legal and other expenses thereafter
reasonably incurred by the indemnified party shall be borne by the indemnifying
party. Neither the indemnifying party nor indemnified party shall be liable for
any settlement of any such action effected without its written consent.

     (d)  If recovery is not available under the foregoing indemnification
provisions of this Section, for any reason other than as specified therein, the
parties entitled to indemnification by the terms thereof shall be entitled to
contribution to liabilities and expenses, except to the extent that contribution
is not permitted under Section 11(f) of the Act. In determining the amount of
contribution to which the respective parties are entitled, there shall be
considered the relative benefits received by each party from the offering of the
Purchased Bonds (taking into account the portion of the proceeds of the offering
realized by each), the parties' relative knowledge and access to information
concerning the matter with respect to which the claim was asserted, the
opportunity to correct and prevent any statement

                                       12
<PAGE>   13
        or omission, and any other equitable considerations appropriate under
        the circumstances. The Company and the Underwriters agree that it would
        not be equitable if the amount of such contribution were determined by
        pro rata or per capita allocation. The Underwriters or person 
        controlling such Underwriters shall not be obligated to make 
        contribution hereunder which in the aggregate exceeds the total public
        offering price of the Purchased Bonds less the aggregate amount of any
        damages which the Underwriters and their controlling persons have 
        otherwise been required to pay in respect of the same claim or any 
        substantially similar claim.

        7.  Default of Underwriters. If any Underwriter or Underwriters default
in their obligations to purchase the Purchased Bonds hereunder on the Closing
Date and the aggregate principal amount of Purchased Bonds which such
defaulting Underwriter or Underwriters agreed but failed to purchase does not
exceed 10% of the aggregate principal amount of the Purchased Bonds which the
Underwriters are obligated to purchase on the Closing Date, you may make
arrangements satisfactory to the Company for the purchase of such Purchased
Bonds by other persons, including any of the Underwriters, but if no such
arrangements are made by the Closing Date the non-defaulting Underwriters shall
be obligated severally, in proportion to their respective commitments
hereunder, to purchase the Purchased Bonds which such defaulting Underwriters
agreed but failed to purchase on the Closing Date. If any Underwriter or
Underwriters so default and the aggregate principal amount of the Purchased
Bonds with respect to which such default or defaults occur is more than the
above percentage and arrangements satisfactory to you and the Company for the
purchase of such bonds by other persons are not made within thirty-six hours
after such default, this Agreement will terminate without liability on the part
of any non-defaulting Underwriter or the Company, except as provided in 
Section 8 hereof. In the event that any Underwriter or Underwriters default in
their obligations to purchase the Purchased Bonds hereunder, the Company may by
prompt written notice to you postpone the Closing Date for a period of not more
than seven full business days in order to effect whatever changes may thereby be
made necessary in the Registration Statement or the Prospectus or in any other
documents, and the Company will promptly file any amendments to the Registration
Statement or supplements to the Prospectus which may thereby be made necessary.
As used in this Agreement, the term "Underwriter" includes any person
substituted for an Underwriter under this Section 7. Nothing herein will relieve
a defaulting Underwriter, from liability for its default.

        8.  Survival of Representations, Warranties, etc. The respective
representations, warranties, agreements and indemnities of the Company and the
Underwriters set forth in or made pursuant to this Agreement will remain in
full force and effect, regardless of any investigation, or statement as to the
results thereof, made by or on behalf of the Underwriters or the Company or any
of their officers or directors or any controlling person, and will survive
delivery of any payment for the Purchased Bonds.

        9.  Termination of Agreement. The Representatives may terminate this
Agreement, by notice to the Company, at any time at or prior to the Closing
Date (i) if there has been, since the date of this Agreement or since the
respective dates as of which information is given in the Registration

                                       13
<PAGE>   14
Statement, any material adverse change in the condition, financial or
otherwise, or in the earnings, or business affairs or business prospects of the
Company and its subsidiaries considered as one enterprise, whether or not
arising in the ordinary course of business, or (ii) if there has occurred any
national or international calamity or crisis, the effect of which is such as to
make it, in the judgment of the Representatives, impracticable to market the
Purchased Bonds or to enforce contracts for the sale of the Purchased Bonds, or
(iii) if trading on the New York Stock Exchange has been suspended, or if a
banking moratorium has been declared by either Federal or New York authorities.
If this Agreement is terminated pursuant to this Section 9, such termination
shall be without liability of any party to any other party except as provided
in Section 8 hereof.

        10.  Notice. All communications hereunder shall be in writing and if
sent to the Company will be mailed, delivered or transmitted via facsimile and
confirmed to it at 500 South 27th Street, Decatur, Illinois 62525 and if sent
to any of the Underwriters will be mailed, delivered or transmitted via
facsimile and confirmed to such addresses as the Representatives of the
Underwriters shall advise the Company in writing.

        11. Successors. This Agreement will inure to the benefit of and be
binding upon the parties hereto and their respective successors and the
officers and directors and controlling persons referred to in Section 6 hereof,
and no other person will have any right or obligation hereunder.

        12.  Counterparts. This Agreement may be executed in counterparts all
of which, taken together, shall constitute a single agreement among the parties
to such counterparts.

        13.  Representation of the Underwriters. The Representatives represent
and warrant to the Company that they are authorized to act as the
representatives of the Underwriters in connection with this financing, and the
Representatives' execution and delivery of this Agreement and any action under
this Agreement taken by such Representatives will be binding upon all 
Underwriters.

        14.  Interpretation When No Representatives. In the event no
Underwriters are named in Schedule II hereto, the term "Underwriters" shall be
deemed for all purposes of this Agreement to be the Underwriter or Underwriters
named as such in Schedule I hereto, the principal amount of the Purchased Bonds
to be purchased by any such Underwriter shall be that set forth opposite its
name in Schedule I hereto and all reference to the "Representatives" shall be
deemed to be the Underwriter or Underwriters named in such Schedule I.

                            [Signature Page Follows]


                                       14
<PAGE>   15
     If the foregoing is in accordance with your understanding of our
agreement, kindly sign and return to us the enclosed duplicate hereof,
whereupon it will become a binding agreement between the Company and the
Underwriters in accordance with its terms.


                                             Very truly yours,

                                             ILLINOIS POWER COMPANY


                                             By: ____________________________
                                             Its:____________________________


Accepted as of the date of this Underwriting
Agreement set forth in Schedule I hereto.

____________________________________________ ,
as Representatives


By: ____________________________
Its:____________________________


                                       15




<PAGE>   16
                                   SCHEDULE I

                   NEW MORTGAGE BONDS, ____% SERIES DUE _____

Name and address of Representatives:


     ______________________________________

     ______________________________________

     ______________________________________

Purchase Price and Description of Purchased Bonds:

     Principal Amount:  $ _________________

     Purchase Price:  ____% of the Principal Amount

     Interest Rate:  ____%

     Initial Public Offering Price:  ____%

     Selling Concession:  ____%

     Reallowance to Dealers:  ____%

     Maturity:  ______

     Sinking Fund Provisions:  ______

     Redemption Provisions:  ___________________________________________________

Other Provisions:  _____________________________________________________________

     Time and Date of Delivery and Payment (the "Closing Date")

          Date:  _______________

          Time:  _______________

          Place of Delivery of Purchased Bonds:  ______________________

          Type of Funds:  _________________________


                                      I-1
<PAGE>   17
          Method of Payment:  _________________

          Underwriting Agreement Dated:  ___________, ____________



                                      I-2
<PAGE>   18
                                  SCHEDULE II

<TABLE>
<CAPTION>
                                                       PRINCIPAL AMOUNT OF
NAME OF UNDERWRITER                                      PURCHASED BONDS
- -------------------                                    -------------------
<S>                                                    <C>





                                              TOTAL:    $
                                                          ===============
</TABLE>



                                      II-1

<PAGE>   1
                                                                     EXHIBIT 1.2

                             ILLINOIS POWER COMPANY

                            UNSECURED DEBT SECURITIES

                             UNDERWRITING AGREEMENT

                                                         --------------, -------
                                                               Chicago, Illinois

To the Representative(s) named in Schedule I hereto of the Underwriters named in
Schedule II hereto.

Dear Sirs:

         Illinois Power Company, an Illinois corporation (the "Company"),
proposes to issue and sell from time to time, in one or more series, its
Unsecured Debt Securities which are registered under the registration statement
referred to in Section 1(a) (the "Securities"). The Securities will be issued
under an Indenture, dated as of July 15, 1986, between the Company and The Chase
Manhattan Bank, as Trustee, which provides for the issuance of an unlimited
principal amount of Debt Securities of the Company in one or more series. The
Company proposes to sell to the underwriters named in Schedule II hereto (the
"Underwriters") for whom you are acting as Representative or Representatives
(the "Representatives"), Securities in the aggregate principal amount and of the
series identified in Schedule I hereto ("Purchased Securities").

         1.       REPRESENTATIONS AND WARRANTIES OF THE COMPANY. The Company
represents and warrants to, and agrees with the Underwriters that:

                  (a)      A Registration statement (No. 333-     ), including a
         prospectus, relating to the Securities has been filed with the
         Securities and Exchange Commission (the "Commission") and has become
         effective. Such registration statement, including the prospectus
         therein, as amended and supplemented to the date of this Agreement
         (exclusive of the supplements to the prospectus relating solely to
         Securities that are not the Purchased Securities) and as supplemented
         by the Prospectus Supplement to be included as part of the prospectus
         to be filed with the Commission pursuant to Rule 424 (c) under the
         Securities Act of 1933 ("Act") as provided in Section 3(a) hereof, are
         hereinafter referred to as the "Registration Statement" and such
         prospectus is hereinafter referred to as the "Prospectus." Any
         reference herein to the Registration Statement or the Prospectus shall
         be deemed to include the document incorporated by reference therein
         pursuant to Item 12 of Form S-3 which were filed under the Securities
         Exchange Act of 1934 ("Exchange Act") on or before the date of this
         Agreement; and any reference herein to the terms "amend," "amendment"
         or "supplement" with respect to the Registration Statement or the
         Prospectus shall be deemed to refer to and include the filing of any
         document under the Exchange Act deemed to be incorporated therein by
         reference after the date of this Agreement.

                  (b)      The Registration Statement and the Prospectus, both
         at the time the Prospectus is filed with the Commission pursuant to
         Rule 424(c) under the Act as provided in Section 3(a) hereof, and any
         further amendments and supplements to the Prospectus when they become
         effective or are filed with the Commission, as the case may be, prior
         to the Closing Date, will conform in all respects to the requirements
         of the Act, the Trust Indenture Act of 1939 ("Trust Indenture Act") and
         the rules
<PAGE>   2
         and regulations of the Commission ("Rules and Regulations"), and none
         of such documents will include any untrue statement of a material fact
         or omit to state any material fact required to be stated therein or
         necessary to make the statements therein not misleading, except that
         the foregoing does not apply to statements or omissions in such
         documents based upon written information furnished to the Company by
         any Underwriter specifically for use therein or in reliance upon and in
         conformity with the Form T-l of the Trustee.

         2.       PURCHASE, OFFERING AND DELIVERY. Subject to the terms and
conditions herein set forth, the Company agrees to sell to each Underwriter, and
each Underwriter agrees, severally and not jointly, to purchase from the
Company, at the purchase price set forth in Schedule I hereto, the principal
amount of the Purchased Securities set forth opposite such Underwriter's name in
Schedule II hereto. It is understood that the Underwriters propose to offer the
Purchased Securities for sale to the public as set forth in the Prospectus
Supplement relating to the Purchased Securities.

         The Purchased Securities to be purchased by each Underwriter shall be
delivered by the Company for the account of such Underwriter to the place
specified in Schedule I hereto against payment of the purchase price therefor by
such Underwriter or on its behalf by certified or official check or checks in
immediately available funds drawn to the order of the Company, at the location
and at the time and date specified in Schedule I hereto or at such other time
and date as the Representatives and the Company may agree, such time and date
being herein referred to as the "Closing Date." The Purchased Securities so to
be delivered will be in fully registered form in such authorized denominations
and registered in such names as the Representatives request at least four full
business days before the Closing Date and will be made available for checking
and packaging in the city designated in Schedule I as the place of delivery at
least 24 hours prior to the Closing Date.

         3.       COVENANTS OF THE COMPANY. The Company covenants and agrees
with the Underwriters that:

                  (a)      Promptly following execution of this Agreement, the
         Company will cause the Prospectus (including as part thereof a
         prospectus supplement relating to the Purchased Securities ("Prospectus
         Supplement")) to be filed with the Commission pursuant to Rule 424(c)
         under the Act the Company will promptly advise the Representatives when
         such filing has been made. Prior to such filing the Company will work
         with the Representatives in the preparation of the Prospectus
         Supplement to assure that the Representatives have no reasonable
         objection to the form or content thereof when filed.

                  (b)      If at any time when a prospectus relating to the
         Purchased Securities is required to be delivered under the Act any
         event occurs as a result of which the Prospectus as then amended or
         supplemented would include an untrue statement of a material fact, or
         omit to state any material fact necessary to make the statements
         therein, in the light of the circumstances under which they were made,
         not misleading, or if it is necessary at any time to amend or
         supplement the Registration Statement or Prospectus to comply with the
         Act or the Rules and Regulations, the Company promptly will prepare and
         file with the Commission an amendment or supplement which will correct
         such statement or omission, or an amendment which will effect such
         compliance.


                                        2
<PAGE>   3
                  (c)      The Company will furnish to each Underwriter such
         number of copies of the Prospectus as may be reasonably requested in
         connection with the offering of the Purchased Securities.

                  (d)      The Company will pay all expenses incident to the
         performance of its obligations under this Agreement, and will reimburse
         the Underwriters for any expenses up to $___________ in the aggregate
         (including fees and disbursements of counsel) incurred in connection
         with qualification of the Purchased Securities for sale and
         determination of their eligibility for investment under the laws of
         such jurisdictions as the Representatives designate and the printing of
         memoranda relating thereto.

         4. CONDITIONS TO THE OBLIGATIONS OF THE UNDERWRITERS. The obligation of
the several Underwriters to purchase and pay for the Purchased Securities
hereunder will be subject to the accuracy of the representations and warranties
on the part of the Company herein, to the performance by the Company of its
obligations hereunder and to the following additional conditions precedent:

                  (a)      Subsequent to the execution and delivery of this
         Agreement there shall not have occurred any change, or any development
         involving a prospective change, in or affecting particularly the
         business or properties of the Company or its subsidiaries which, in the
         judgment of a majority in interest of the Underwriters, including you,
         materially impairs the investment quality of the Purchased Securities.

                  (b)      No stop order suspending the effectiveness of the
         Registration Statement shall have been issued and no proceedings for
         that purpose shall have been instituted or, to the knowledge of the
         Company, or the Underwriters, shall be contemplated by the Commission.

                  (c)      The Underwriters shall have received the following:

                           (i)      A letter of Price Waterhouse, dated the
         Closing Date, confirming that they are independent accountants within
         the meaning of the Act and the Rules and Regulations, and stating in
         effect that (i) in their opinion, the financial statements examined by
         them and incorporated by reference in the Prospectus comply as to form
         in all material respects with the accounting requirements of the Act
         and the Rules and Regulations applicable to annual reports on Form 10-K
         (ii) on the basis of a reading of the interim financial statements
         referred to in clause (A) below, a reading of the latest available
         interim financial statements of the Company, a reading of the minutes
         of the Board of Directors and stockholders of the Company as set forth
         in the minute books of the Company and inquiries of officials of the
         Company responsible for financial and accounting matters, nothing came
         to their attention that caused them to believe that (A) the unaudited
         financial statements included in the most recent Quarterly Report on
         Form 10-Q incorporated by reference in the Prospectus were not prepared
         on a basis substantially consistent with that of the audited financial
         statements as of and for the fiscal year ended December 31, 199__
         incorporated by reference in the Prospectus, or (B) at the date of the
         latest available balance sheet read by such accountants or at a
         subsequent specified date not more than five days prior to the Closing
         Date, there was any change in the capital stock or long term debt of
         the Company or, at the date of the latest available balance sheet read
         by such accountants, there was any decrease in net assets, in each case
         as compared with the corresponding amounts shown in the December


                                        3
<PAGE>   4
         31, 199__ balance sheet incorporated by reference in the Prospectus, or
         (C) for the period of twelve months ended with the closing date of the
         latest available income statement read by such accountants there were
         any decreases, as compared with the twelve months ended December 31,
         199__ in operating revenues, operating income, net income, earnings per
         share of common stock or the ratio of earnings to fixed charges, except
         in all cases set forth in clauses (B) and (C) above for changes or
         decreases which the Prospectus discloses have occurred or may occur, or
         which are described in such letter, and (iii) they have compared the
         dollar amounts (or percentages derived from such dollar amounts) and
         other financial information contained in the Prospectus under the
         captions "Summary Information," "Ratio of Earnings to Fixed Charges"
         and "Description of Unsecured Debt Securities" and contained in the
         Company's Annual Report on Form 10-K for the year ended December 31,
         199__ (which is incorporated by reference in the Prospectus) (in each
         case to the extent that such dollar amounts, percentages and other
         financial information are derived from the general accounting records
         of the Company subject to the internal controls of the Company's
         accounting system or are derived directly from such records by analysis
         or computation) with the results obtained from inquiries, a reading of
         such general accounting records and other procedures specified in such
         letter, and have found such dollar amounts, percentages and other
         financial information to be in agreement with such results, except as
         otherwise specified in such letter. All financial statements included
         in material incorporated by reference in the Prospectus shall be deemed
         included in the Prospectus for purposes of this subsection.

                           (ii)     An opinion of Schiff Hardin & Waite, counsel
         for the Company, dated the Closing Date, to the effect that:

                                    (A)      The Company has been duly
                  incorporated and is validly existing as a corporation in good
                  standing under the laws of the State of Illinois, with
                  corporate power and authority to own its properties and
                  conduct its business as described in the Prospectus; and the
                  Company is not required to be qualified as a foreign
                  corporation in any jurisdiction.

                                    (B)      The Purchased Securities have been
                  duly authorized, executed, authenticated, issued and delivered
                  and constitute the valid and binding obligations of the
                  Company enforceable in accordance with their terms, and
                  (subject to the qualifications mentioned in subparagraph (C)
                  below with respect to the enforceability of the Indenture and
                  to any variations established for any particular series of
                  Securities) are entitled to the benefit of the Indenture in
                  accordance with the terms thereof equally and ratably with all
                  other securities issued under the Indenture.

                                    (C)      The Indenture has been duly
                  authorized, executed and delivered and is a valid and binding
                  instrument enforceable in accordance with its terms, except as
                  the same may be limited by bankruptcy, insolvency,
                  reorganization or other laws relating to or affecting the
                  enforcement of creditors' rights generally.

                                    (D)      The Registration Statement has
                  become effective under the Act; the Indenture has been duly
                  qualified under the Trust Indenture Act; to the best of the


                                        4
<PAGE>   5
                  knowledge of such counsel, no stop order suspending the
                  effectiveness of the Registration Statement has been issued
                  and no proceedings for that purpose have been instituted or
                  are pending or contemplated under the Act, and the
                  Registration Statement and the Prospectus, and each amendment
                  or supplement thereto, as of their respective effective or
                  issue dates, complied as to form in all material respects with
                  the requirements of the Act, the Trust Indenture Act and the
                  Rules and Regulations; such counsel have no reason to believe
                  that either the Registration Statement or the Prospectus, or
                  any such amendment or supplement, as of such respective dates,
                  contained any untrue statement of a material fact or omitted
                  to state any material fact required to be stated therein or
                  necessary to make the statements therein not misleading; the
                  descriptions in the Registration Statement and Prospectus of
                  statutes, legal and governmental proceedings and contracts and
                  other documents are accurate and fairly present the
                  information required to be shown; and such counsel do not know
                  of any legal or governmental proceedings required to be
                  described in the Prospectus which are not described as
                  required, nor of any contracts or documents of a character
                  required to be described in the Registration Statement or
                  Prospectus or to be filed as Exhibits to the Registration
                  Statement which are not described and filed as required; it
                  being understood that such counsel need express no opinion as
                  to the financial statements or other financial data contained
                  in Registration Statement or the Prospectus.

                                    (E)      This Agreement has been duly
                  authorized, executed and delivered by the Company.

                                    (F)      The Illinois Commerce Commission
                  has entered an order permitting the issue and sale of the
                  Purchased Securities; and said order is valid and in effect
                  and no further approval, authorization, consent or order of,
                  or action by, any other regulatory authority is necessary with
                  respect to the execution and delivery of the Indenture or the
                  issue and sale of the Purchased Securities, as contemplated by
                  this Agreement, it being understood that in giving such
                  opinion such counsel are not passing upon the authorizations
                  or approvals which may be necessary under the securities or
                  blue sky laws of any jurisdiction. The issue and sale of the
                  Purchased Securities, as contemplated by this Agreement, is in
                  conformity with the terms of said order of the Illinois
                  Commerce Commission.

                                    (G)      The statements made in the
                  Prospectus under the caption "Description of the Unsecured
                  Debt Securities" insofar as they purport to summarize
                  provisions of the documents specifically referred to under
                  said caption, fairly present the information called for with
                  respect thereto by Form S-3.

                                    (H)      The statements in the Prospectus
                  and in the Company's most recent Annual Report on Form 10- K
                  (which is incorporated by reference in the Prospectus) as to
                  matters of law and legal conclusions which are stated n the
                  Prospectus to have been made on the authority of such counsel
                  have been reviewed by them and, as to matters of law and legal
                  conclusions, are correct.


                                        5
<PAGE>   6
                           (iii)    An opinion from ___________, counsel for the
         Underwriters, as to those matters as the Underwriters may reasonably
         require.

                           (iv)     A certificate of the Chairman, President, an
         Executive Vice President, a Senior Vice President or a Vice President
         and the Treasurer or the principal financial or accounting officer of
         the Company, dated the Closing Date, in which such officers, to the
         best of their knowledge after reasonable investigation, shall state
         that the representations and warranties of the Company in this
         Agreement are true and correct, that the Company has complied with all
         agreements and satisfied all conditions on its part to be performed or
         satisfied at or prior to the Closing Date that no stop order suspending
         the effectiveness of the Registration Statement has been issued and no
         proceedings for that purpose have been instituted or are contemplated
         by the Commission, and that, subsequent to the date of the most recent
         financial statements in the Prospectus, there has been no material
         adverse change in the financial position or results of operations of
         the Company except as set forth or contemplated in the Prospectus or as
         described in such certificate.

                           (v)      An order of the Illinois Commerce Commission
         authorizing the issuance and sale of the Purchased Securities in
         accordance with the terms and conditions hereof shall be in full force
         and effect and shall contain no conditions or provision unacceptable to
         Underwriters, it being understood that no order in effect as of the
         date hereof contains any such unacceptable condition or provision.

The Company will furnish the Underwriters with such conformed copies of such
opinions, certificates, letters and documents as the Underwriters reasonably
request.

         5.       CONDITIONS OF THE OBLIGATION OF THE COMPANY. The obligation of
the Company to sell and deliver the Purchased Securities on the Closing Date is
subject to the following conditions precedent:

                  (a)      Prior to the Closing Date, no stop order suspending
         the effectiveness of the Registration Statement shall have been issued
         and no proceedings for that purpose shall have instituted, or, to the
         knowledge of the Company or the Underwriters, shall be contemplated by
         the Commission.

                  (b)      There shall be in effect on the Closing Date an order
         of the Illinois Commerce Commission authorizing the issuance and sale
         of the Purchased Securities in accordance with the terms and conditions
         thereof, and no order of the Illinois Commerce Commission shall be in
         effect at the Closing Date, which would prevent the sale and delivery
         of the Purchased Securities or which contains any condition or
         provision with respect to such sale which is not acceptable to the
         Company, it being understood that no order in effect at the date of
         this Agreement contains any such unacceptable condition or provision.

         If any such condition shall not have been satisfied, then the Company
shall be entitled, by notice in writing to the Underwriters, to terminate this
Agreement without liability on the part of the Company or any Underwriter,
except as provided herein.


                                        6
<PAGE>   7
         6.       INDEMNIFICATION.

                  (a)      The Company will indemnify and hold harmless each
         Underwriter and each person, if any, who controls any Underwriter
         within the meaning of the Act against any losses, claims, damages or
         liabilities, joint or several, to which such Underwriter or such
         controlling person may become subject, under the Act or otherwise,
         insofar as such losses, claims, damages or liabilities (or actions in
         respect thereof) arise out of or are based upon any untrue statement or
         alleged untrue statement of any material fact contained in the
         Registration Statement, the Prospectus, or any amendment or supplement
         thereto, or arise out of or are based upon the omission or alleged
         omission to state therein a material fact required to be stated therein
         or necessary to make the statements therein not misleading; and will
         reimburse each Underwriter and each such controlling person for any
         legal or other expenses reasonably incurred by such Underwriter or such
         controlling person in connection with investigating or defending any
         such loss, claim, damage, liability or action; provided, however, that
         the Company will not be liable in any such case to the extent that any
         such loss, claim, damage or liability arises out of or is based upon an
         untrue statement or alleged untrue statement or omission or alleged
         omission made in any of such documents in reliance upon and in
         conformity with written information furnished to the Company by any
         Underwriter specifically for use therein or in reliance upon and in
         conformity with the Form T-1 of the Trustee. This indemnity agreement
         will be in addition to any liability which the Company may otherwise
         have.

                  (b)      Each Underwriter will indemnify and hold harmless the
         Company, each of its directors and officers and each person, if any,
         who controls the Company within the meaning of the Act, against any
         losses, claims, damages or liabilities to which the Company or any such
         director, officer or controlling person may become subject, under the
         Act or otherwise, insofar as such losses, claims, damages or
         liabilities (or actions in respect thereof) arise out of or are based
         upon any untrue statement or alleged untrue statement of any material
         fact contained in the Registration Statement, the Prospectus or any
         amendment or supplement thereto, or arise out of or are based upon the
         omission or the alleged omission to state therein a material fact
         required to be stated therein or necessary to make the statements
         therein not misleading, in each case to the extent, but only to the
         extent, that such untrue statement or alleged untrue statement or
         omission or alleged omission was made in reliance upon and in
         conformity with written information furnished to the Company by such
         Underwriters specifically for use therein; and will reimburse any legal
         or other expenses reasonably incurred by the Company or any such
         director, officer or controlling person in connection with
         investigating or defending any such loss, claim, damage, liability or
         action. This indemnity agreement will be in addition to any liability
         which such Underwriters may otherwise have.

                  (c)      Promptly after receipt by an indemnified party under
         this Section of notice of the commencement of any action, such
         indemnified party will, if a claim in respect thereof is to be made
         against the indemnifying party under this Section, notify the
         indemnifying party of the commencement thereof; but the omission so to
         notify the indemnifying party will not relieve it from any liability
         which it may have to any indemnified party otherwise than under this
         Section. In case any such action is brought against any indemnified
         party, and it notifies the indemnifying party of the commencement


                                        7
<PAGE>   8
         thereof the indemnifying party will be entitled to participate therein
         and, to the extent that it may wish, jointly with any other
         indemnifying party similarly notified, to assume the defense thereof,
         with counsel satisfactory to such indemnified party (who shall not,
         except with the consent of the indemnified party, be counsel to the
         indemnifying party) , and after notice from the indemnifying party to
         such indemnified party of its election so to assume the defense
         thereof, the indemnifying party will not be liable to such indemnified
         party under this Section for any legal or other expenses subsequently
         incurred by such indemnified party in connection with the defense
         thereof other than reasonable costs of investigation.

                  (d)      If recovery is not available under the foregoing
         indemnification provisions of this Section, for any reason other than
         as specified therein, the parties entitled to indemnification by the
         terms thereof shall be entitled to contribution for liabilities and
         expenses, except to the extent that contribution is not permitted under
         Section 11(f) of the Act. In determining the amount of contribution to
         which the respective parties are entitled, there shall be considered
         the relative benefits received by each party from the offering of the
         Purchased Securities (taking into account the portion of the proceeds
         of the offering realized by each) , the parties' relative knowledge and
         access to information concerning the matter with respect to which the
         claim was asserted, the opportunity to correct and prevent any
         statement or omission, and any other equitable considerations
         appropriate under the circumstances. The Company and the Underwriters
         agree that it would not be equitable if the amount of such contribution
         were determined by pro rata or per capita allocation. The Underwriters
         or person controlling such Underwriters shall not be obligated to make
         contribution hereunder which in the aggregate exceeds the total public
         offering price of the Purchased Securities less the aggregate amount of
         any damages which the Underwriters and their controlling persons have
         otherwise been required to pay in respect of the same claim or any
         substantially similar claim.

         7.       DEFAULT OF UNDERWRITERS. If any Underwriter or Underwriters
default in their obligations to purchase the Purchased Securities hereunder on
the Closing Date and the aggregate principal amount of Purchased Securities
which such defaulting Underwriter or Underwriters agreed but failed to purchase
does not exceed 10% of the aggregate principal amount of the Purchased
Securities which the Underwriters are obligated to purchase on the Closing Date,
you may make arrangements satisfactory to the Company for the purchase of such
Purchased Securities by other persons, including any of the Underwriters, but if
no such arrangements are made by the Closing Date the non-defaulting
Underwriters shall be obligated severally, in proportion to their respective
commitments hereunder, to purchase the Purchased Securities which such
defaulting Underwriters agreed but failed to purchase on the Closing Date. If
any Underwriter or Underwriters so default and the aggregate principal amount of
the Purchased Securities with respect to which such default or defaults occur is
more than the above percentage and arrangements satisfactory to you and the
Company for the purchase of such Purchased Securities by other persons are not
made within thirty-six hours after such default, this Agreement will terminate
without liability on the part of any non-defaulting Underwriter or the Company,
except as provided in Section 8. In the event that any Underwriter or
Underwriters default in their obligations to purchase the Purchased Securities
hereunder, the Company may, by prompt written notice to you, postpone the
Closing Date for a period of not more than seven full business days in order to
effect whatever changes may thereby be made necessary in the Registration
Statement or the Prospectus or the Registration Statement or


                                        8
<PAGE>   9
supplements to the Prospectus which may thereby be made necessary. As used in
this Agreement, the term "Underwriter" includes any person substituted for an
Underwriter under this Section. Nothing herein will relieve a defaulting
Underwriter from liability for its default.

         8.       SURVIVAL OF REPRESENTATIONS, WARRANTIES, ETC. The respective
representations, warranties, agreements and indemnities of the Company and the
Underwriters set forth in or made pursuant to this Agreement will remain in full
force and effect, regardless of any investigation, or statement as to the
results thereof, made by or on behalf of the Underwriters or the Company or any
of their officers or directors or any controlling person, and will survive
delivery of any payment for the Purchased Securities.

         9.       NOTICE. All communications hereunder shall be in writing and
if sent to the Company will be mailed, delivered or transmitted via facsimile
and confirmed to it at 500 South 27th Street, Decatur, Illinois 62525 and if
sent to any of the Underwriters will be mailed, delivered or transmitted via
facsimile and confirmed to such addresses as the Representatives of the
Underwriters shall advise the Company in writing.

         10.      SUCCESSORS. This Underwriting Agreement will inure to the
benefit of and be binding upon the parties hereto and their respective
successors and the officers and directors and controlling persons referred to in
Section 6, and no other person will have any right or obligation hereunder.

         11.      COUNTERPARTS. This Agreement may be executed in counterparts
all of which, taken together, shall constitute a single agreement among the
parties to such counterparts.

         12.      REPRESENTATION OF THE UNDERWRITERS. The Representatives
represent and warrant to the Company that they are authorized to act as the
representatives of the Underwriters in connection with this financing, and the
Representatives' execution and delivery of this Agreement and any action under
this Agreement taken by such Representatives will be binding upon all
Underwriters.

         13.      INTERPRETATION WHEN NO REPRESENTATIVES. In the event no
Underwriters are named in Schedule II hereto, the term "Underwriters" shall be
deemed for all purposes of this Agreement to be the Underwriter or Underwriters
named as such in Schedule I hereto, the principal amount of the Purchased
Securities to be purchased by any such Underwriter shall be that set forth
opposite its name in Schedule I hereto and all reference to the
"Representatives" shall be deemed to be the Underwriter or Underwriters named in
Schedule I.


                                        9
<PAGE>   10
         If the foregoing is in accordance with your understanding of our
agreement, kindly sign and return to us the enclosed duplicate hereof, whereupon
it will become a binding agreement between the Company and the Underwriters in
accordance with its terms.


                                                   Very truly yours,

                                                   Illinois Power Company



                                                   By___________________________
                                                     Its________________________


Accepted as of the date of this
Underwriting Agreement set forth
in Schedule I hereto.

__________________________________,
   as Representatives


By________________________________
  Its_____________________________


                                       10
<PAGE>   11
                                   SCHEDULE I

[Representatives of the] Underwriters and addresses [and any Principal Amount of
Purchased Securities if no Underwriters named in Schedule II].

Purchase Price and Description of Purchased Securities:

         Aggregate Principal Amount: $_______

         Purchase price:_______% of the Principal Amount

         Interest Rate:_______%

         Initial Public Offering Price:_______%

         Dealer Discount:_______%

         Reallowance to Dealers:_______%

         Maturity:_______

         Sinking Fund Provisions:_______

         Redemption Provisions:_______

         Other Provisions:_______

Time and Date of Delivery and Payment ("Closing Date"):

         Date:_______

         Time:_______

         Place of delivery of payment:_______

         Type of Funds:_______

         Method of payment:_______

         Place of delivery of Purchased Securities:_______

         Underwriting Agreement Dated:_______



                                       11
<PAGE>   12
                                   SCHEDULE II

                                           Principal
                                           Amount of
                                           Purchased
Underwriter                                Securities
- -----------                                ----------






                                       12

<PAGE>   1
                                                                    EXHIBIT 4.39



================================================================================




                             ILLINOIS POWER COMPANY


                                       TO


                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE


                                  -------------




                          SUPPLEMENTAL INDENTURE NO. 1

                            DATED AS OF MARCH 1, 1998


                                       TO


                           MORTGAGE AND DEED OF TRUST

                             DATED NOVEMBER 1, 1943



================================================================================
- -


<PAGE>   2




SUPPLEMENTAL INDENTURE No. 1 dated as of March 1, 1998 ("Supplemental Indenture
No. 1"), made by and between ILLINOIS POWER COMPANY, a corporation organized and
existing under the laws of the State of Illinois (the "Company"), party of the
first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the Mortgage and Deed of Trust dated November 1, 1943, hereinafter
mentioned, party of the second part;

         WHEREAS, the Company has heretofore executed and delivered its Mortgage
and Deed of Trust dated November 1, 1943 ("Original Indenture"), to the Trustee,
for the security of the First Mortgage Bonds of the Company issued and to be
issued thereunder (the "Bonds"); and

         WHEREAS, pursuant to the terms and provisions of the Original Indenture
there were created and authorized by Supplemental Indentures thereto bearing the
following dates, respectively, the First Mortgage Bonds of the series issued
thereunder and respectively identified opposite such dates:


<TABLE>
<CAPTION>
          DATE OF
        SUPPLEMENTAL              IDENTIFICATION
          INDENTURE                  OF SERIES                              CALLED
        ------------             ----------------                  ---------------------
<S>                            <C>                                 <C>        
November 1, 1943               4% Series due 1973                  Bonds of the 1973 Series
                                   (redeemed)
March 1, 1946                  2 7/8% Series due 1976              Bonds of the 1976 Series
                                        (paid at
                                        maturity)
February 1, 1948               3 1/2% Series due 1978              Bonds of the 1978 Series
                                        (paid at
                                        maturity)
July 1, 1949                   2 7/8 % Series due 1979             Bonds of the 1979 Series
                                        (paid at                    
                                        maturity)
April 1, 1950                  2 3/4% Series due 1980              Bonds of the 1980 Series
                                        (paid at
                                        maturity)
March 1, 1952                  3 1/2% Series due 1982              Bonds of the 1982 Series
                                        (paid at
                                        maturity)
November 1, 1953               3 1/2% Series due 1983              Bonds of the 1983 Series
                                         (paid at
                                    maturity)
July 1, 1956                   3 3/4% Series due 1986              Bonds of the 1986 Series
                                        (paid at
                                        maturity)

</TABLE>


<PAGE>   3
<TABLE>
<CAPTION>
          DATE OF
        SUPPLEMENTAL              IDENTIFICATION
          INDENTURE                  OF SERIES                              CALLED
        ------------             ----------------                  ---------------------
<S>                            <C>                                 <C>        
May 1, 1958                    4% Series due 1988                  Bonds of the 1988 Series
                                   (redeemed)
January 1, 1963                4 1/4% Series due 1993              Bonds of the 1993 Series
                                    (paid at
                                     maturity)
October 1, 1966                5.85% Series due 1996               Bonds of the 1996 Series
                                    (paid at
                                     maturity)
January 1, 1968                6 3/8% Series due 1998              Bonds of the First 1998
                                   (redeemed)                      Series
October 1, 1968                6 3/4% Series due October           Bonds of the Second 1998
                               1, 1998 (redeemed)                  Series
October 1, 1969                8.35% Series due 1999               Bonds of the First 1999
                                   (redeemed)                      Series
November 1, 1970               9% Series due 2000                  Bonds of the 2000 Series
                                   (redeemed)
October 1, 1971                7.60% Series due 2001               Bonds of the 2001 Series
                                   (redeemed)
June 1, 1973                   7 5/8% Series due 2003              Bonds of the First 2003
                                   (redeemed)                      Series
May 1, 1974                    Pollution Control                   Bonds of the Pollution
                               Series A                            Control Series A
September 1, 1974              10 1/2% Series due 2004             Bonds of the First 2004
                                   (redeemed)                      Series
July 1, 1976                   8 3/4% Series due 2006              Bonds of the 2006 Series
                                   (redeemed)
May 1, 1977                    Pollution Control                   Bonds of Pollution Control
                               Series B                            Series B
November 1, 1977               8 1/4% Series due 2007              Bonds of the 2007 Series
                                   (redeemed)
August 1, 1978                 8 7/8% Series due 2008              Bonds of the 2008 Series
                                   (redeemed)
July 1, 1979                   9 7/8% Series due July 1,           Bonds of the Second 2004
                               2004                                Series
                                   (redeemed)

</TABLE>

                                       -2-

<PAGE>   4
<TABLE>
<CAPTION>
    DATE OF
        SUPPLEMENTAL              IDENTIFICATION
          INDENTURE                  OF SERIES                              CALLED
        ------------             ----------------                  ---------------------
<S>                            <C>                                 <C>        
July 31, 1980                  11 3/8% Series due 1987             Bonds of the 1987 Series
                                   (redeemed)
August 1, 1980                 12 5/8% Series due 2010             Bonds of the 2010 Series
                                   (redeemed)
July 1, 1982                   14 1/2% Series due 1990             Bonds of the 1990 Series
                                   (redeemed)
November 1, 1982               12% Series due 2012                 Bonds of the 2012 Series
                                   (redeemed)
December 15, 1983              Pollution Control                   Bonds of the Pollution
                               Series C                            Control Series C
                                   (redeemed)
May 15, 1984                   Pollution Control                   Bonds of the Pollution
                               Series D                            Control Series D
                                   (redeemed)
March 1, 1985                  Pollution Control                   Bonds of the Pollution
                               Series E                            Control  Series E
                                   (redeemed)
February 1, 1986               10 1/2% Series due 2016             Bonds of the First 2016
                                   (redeemed)                      Series
July 1, 1986                   9 7/8% Series due 2016              Bonds of the Second 2016
                                   (redeemed)                      Series
September 1, 1986              9 3/8% Series due 2016              Bonds of the Third 2016
                                   (redeemed)                      Series
February 1, 1987               Pollution Control                   Bonds of the Pollution
                               Series F                            Control  Series F
                                   (redeemed)
February 1, 1987               Pollution Control                   Bonds of the Pollution
                               Series G                            Control  Series G
                                   (redeemed)
February 1, 1987               Pollution Control                   Bonds of the Pollution
                               Series H                            Control Series H
                                   (redeemed)
July 1, 1987                   Pollution Control                   Bonds of the Pollution
                               Series I                            Control Series I
July 1, 1988                   10% Series due 1998                 Bonds of the Third 1998
                                   (redeemed)                      Series
</TABLE>


                                       -3-

<PAGE>   5

<TABLE>
<CAPTION>
          DATE OF
        SUPPLEMENTAL              IDENTIFICATION
          INDENTURE                  OF SERIES                              CALLED
        ------------             ----------------                  ---------------------
<S>                            <C>                                 <C>        
July 1, 1991                   Pollution Control                   Bonds of the Pollution
                               Series J                            Control  Series J
June 1, 1992                   Pollution Control                   Bonds of the Pollution
                               Series K                            Control  Series K
June 1, 1992                   Pollution Control                   Bonds of the Pollution
                               Series L                            Control  Series L
July 1, 1992                   7.95% Series due 2004               Bonds of the Third 2004
                                                                   Series
July 1, 1992                   8 3/4% Series due 2021              Bonds of the 2021 Series
September 1, 1992              6 1/2% Series due 1999              Bonds of the 1999 Series
February 15, 1993              8% Series due 2023                  Bonds of the 2023 Series
March 15, 1993                 6 1/8% Series due 2000              Bonds of the 2000 Series
March 15, 1993                 6 3/4% Series due 2005              Bonds of the 2005 Series
July 15, 1993                  7 1/2% Series due 2025              Bonds of the 2025 Series

August 1, 1993                 6 1/2% Series due 2003              Bonds of the Second 2003
                                                                   Series
October 15, 1993               5 5/8% Series due 2000              Bonds of the Second 2000
                                                                   Series
November 1, 1993               Pollution Control                   Bonds of the Pollution
                               Series M                            Control Series M
November 1, 1993               Pollution Control                   Bonds of the Pollution
                               Series N                            Control Series N
November 1, 1993               Pollution Control                   Bonds of the Pollution
                               Series O                            Control Series O

April 1, 1997                  Pollution Control                   Bonds of the Pollution
                               Series P                            Control Series P
April 1, 1997                  Pollution Control                   Bonds of the Pollution
                               Series Q                            Control Series Q
April 1, 1997                  Pollution Control                   Bonds of the Pollution
                               Series R                            Control Series R
</TABLE>


                                       -4-

<PAGE>   6




and

         WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Original Indenture, to be known as Pollution Control Series S
Bonds (the "Pollution Control Series S Bonds") and to issue additional Bonds
under the Original Indenture; and

         WHEREAS, the Pollution Control Series S Bonds, are to be issued to
Harris Trust and Savings Bank, as trustee (the "New Mortgage Trustee") under the
Company's General Mortgage Indenture and Deed of Trust dated as of November 1,
1992 (the "New Mortgage") and are to be owned and held by the New Mortgage
Trustee as "Pledged Bonds" (as defined in the New Mortgage) in accordance with
the terms of the New Mortgage; and

         WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Original
Indenture, and pursuant to appropriate resolutions of the Board of Directors,
has duly resolved and determined to make, execute and deliver to the Trustee a
Supplemental Indenture No. 1 in the form hereof for the purposes herein
provided; and

         WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture No. 1 a valid, binding and legal instrument have been
done, performed and fulfilled and the execution and delivery hereof have been in
all respects duly authorized;

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE No. 1 WITNESSETH:

         THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Original Indenture and of One Dollar to it duly paid by
the Trustee at or before the ensealing and delivery of these presents, the
receipt whereof is hereby acknowledged, hereby covenants and agrees to and with
the Trustee and its successors in the trust under the Original Indenture, for
the benefit of the New Trustee and any successor holder of the Bonds as follows:

                                   ARTICLE I.

                DESCRIPTION OF POLLUTION CONTROL SERIES S BONDS.

         SECTION 1. The Company hereby creates a new series of Bonds to be known
as "Pollution Control Series S Bonds." The Pollution Control Series S Bonds
shall be executed, authenticated and delivered in accordance with the provisions
of, and shall in all respects be subject to, all of the terms, conditions and
covenants of the Original Indenture, as supplemented and modified. The Pollution
Control Series S Bonds will be issued only to the New Mortgage Trustee as
security for a series of bonds being issued under the Company's New Mortgage and
the supplemental indenture no. 1 to the New Mortgage dated as of March 1, 1998
("New Mortgage Pollution Control Series S Bonds") and in the same principal
amount as the New Mortgage Pollution Control Series S Bonds.


                                       -5-

<PAGE>   7




         Pollution Control Series S Bonds shall be dated as provided in Section
6 of Article II of the Original Indenture. All Pollution Control Series S Bonds
shall mature on March 1, 2028 and shall bear interest at the rate of five and
four-tenths per cent (5.40%) per annum, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, until the principal sum
is paid in full. Any payment by the Company of principal of , or premium or
interest on, any Pollution Control Series S Bonds shall be applied by the New
Mortgage Trustee to the payment of any principal, premium or interest, as the
case may be, in respect of the New Mortgage Pollution Control Series S Bonds due
in accordance with the terms of the New Mortgage.

         SECTION 2. The Pollution Control Series S Bonds and the Trustee's
Certificate shall be substantially in the following forms respectively:



                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                         POLLUTION CONTROL SERIES S BOND

No. __________                                                       $18,700,000

         ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to Harris Trust and Savings Bank as
trustee (the "New Mortgage Trustee") under the Company's General Mortgage
Indenture and Deed of Trust dated as of November 1, 1992 (the "New Mortgage") or
its respective registered assigns, the principal sum of $18,700,000 on March 1,
2028, in any coin or currency of the United States of America which at the time
of payment is legal tender for public and private debts, and to pay interest in
like coin or currency from March 1, 1998, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, at the rate of five and
four-tenths percent (5.40%) per annum, until said principal sum is paid in full.
Both the principal of, and the interest on, this Bond are payable at the agency
of the Company in the City of Chicago, Illinois.

         This Bond shall not be entitled to any benefit under the Indenture or
any indenture supplemental thereto, or become valid or obligatory for any
purpose, until the form of certificate endorsed hereon shall have been signed by
or on behalf of Harris Trust and Savings Bank, the Trustee under the Indenture,
or a successor trustee thereto under the Indenture (the "Trustee").

         The provisions of this Bond are continued on the reverse hereof and
such continued provisions shall for all purposes have the same effect as though
fully set forth at this place.


                                       -6-

<PAGE>   8




         IN WITNESS WHEREOF, Illinois Power Company has caused this Bond to be
signed (manually or by facsimile signature) in its name by its President or a
Vice President, and its corporate seal (or a facsimile thereof) to be hereto
affixed and attested (manually or by facsimile signature) by its Secretary or an
Assistant Secretary.

Dated ______________, 1998                               ILLINOIS POWER COMPANY,


                                                  By  . . . . . . . . . . . . .
                                                         Vice President

ATTEST:


 . . . . . . . . . . . . . .
    Assistant Secretary



                         [FORM OF TRUSTEE'S CERTIFICATE]

         This Bond is one of the Bonds of the series designated therein,
described in the within-mentioned Indenture and the Supplemental Indenture No. 1
dated as of March 1, 1998.

                                         HARRIS TRUST AND SAVINGS BANK,
                                                                        Trustee,

                                         By . . . . . . . . . . . . . . . . . . 
                                                Authorized Officer

                            [FORM OF REVERSE OF BOND)

         This Bond is one of a duly authorized issue of Bonds of the Company
(the "Bonds") in unlimited aggregate principal amount, of the series hereinafter
specified, all issued and to be issued under and equally secured by the Mortgage
and Deed of Trust (the "Indenture"), dated November 1, 1943, executed by the
Company to Harris Trust and Savings Bank (the "Trustee"), as Trustee, to which
Indenture and all indentures supplemental thereto, including the Supplemental
Indenture dated February 15, 1993, which amended Section 1 of Article IX of the
Indenture, reference is hereby made for a description of the properties
mortgaged and pledged, the nature and extent of the security, the rights of the
registered owners of the Bonds and of the Trustee in respect thereof, and the
terms and conditions upon which the Bonds are, and are to be, secured. The Bonds
may be issued in series, for various principal sums, may mature at different
times, may bear interest at different rates and may otherwise vary as in the
Indenture provided. This Bond is one of a series designated as the "Pollution
Control Series S Bonds" (the "Pollution Control Series S Bonds") of the Company,
unlimited in aggregate principal amount, issued under and secured by the
Indenture and described in the supplemental indenture no. 1 dated as of March 1,


                                       -7-

<PAGE>   9




1998 ("Supplemental Indenture No. 1 of March 1, 1998"), between the Company and
the Trustee, supplemental to the Indenture.

         To the extent permitted by, and as provided in, the Indenture,
modifications or alterations of the Indenture, or of any indenture supplemental
thereto, and of the rights and obligations of the Company and of the holders of
the Bonds and coupons may be made with the consent of the Company by an
affirmative vote of the holders of not less than 662/3% in amount of the Bonds
entitled to vote then outstanding, at a meeting of Bondholders called and held
as provided in the Indenture, and by an affirmative vote of the holders of not
less than 662/3% in amount of the Bonds of any series entitled to vote then
outstanding and affected by such modification or alteration, in case one or more
but less than all of the series of Bonds then outstanding under the Indenture
are so affected; provided however, that no such modification or alteration shall
be made which will affect the terms of payment of the principal of, or interest
or premium, if any, on this Bond.

         This Pollution Control Series S Bond is subject to redemption in
accordance with the terms of Article II of the Supplemental Indenture No. 1 of
March 1, 1998.

         In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the Bonds at any such time outstanding under the Indenture
may be declared or may become due and payable, upon the conditions and in the
manner and with the effect provided in the Indenture. The Indenture provides
that such declaration may in certain events be rescinded by the holders of a
majority in principal amount of the Bonds outstanding.

         No recourse shall be had for the payment of the principal of, or
premium or interest on this Bond, or for any claim based hereon or on the
Indenture or any indenture supplemental thereto, against any incorporator, or
against any stockholder, director or officer, as such, past, present or future,
of the Company, or of any predecessor or successor corporation, either directly
or through the Company or any such predecessor or successor corporation, whether
by virtue of any constitution, statute or rule of law, or by the enforcement of
any assessment or penalty or otherwise, all such liability, whether at common
law, in equity, by any constitution, statute, rule of law, or otherwise, of
incorporators, stockholders, directors or officers being released by every owner
hereof by the acceptance of this Bond and as part of the consideration for the
issue hereof, and being likewise released by the terms of the Indenture;
provided, however, that nothing herein or in the Indenture or any indenture
supplemental thereto contained shall prevent the enforcement of the liability,
if any, of any stockholder or subscriber to capital stock upon or in respect of
shares of capital stock not fully paid up.

         Notwithstanding any provision in the Indenture, the Supplemental
Indenture No. 1 of March 1, 1998 or this Pollution Control Series S Bond to the
contrary, any payment by the Company under the New Mortgage of principal of, or
premium or interest on, bonds which shall have been authenticated and delivered
under the New Mortgage (the "New Mortgage Pollution Control Series S Bonds")
upon the basis of the issuance and delivery to the New Mortgage Trustee of the
Pollution Control

                                       -8-

<PAGE>   10




Series S Bonds shall, to the extent thereof, be deemed to satisfy and discharge
the obligation of the Company to make a payment of principal, premium or
interest, as the case may be, in respect of this Pollution Control Series S Bond
which is then due.

         This Pollution Control Series S Bond constitutes a "Pledged Bond" (as
defined in the New Mortgage) and is subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, this Pollution Control Series
S Bond shall be subject to surrender by the New Mortgage Trustee in accordance
with the provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Indenture, the Supplemental Indenture No. 1 of March 1, 1998
or this Pollution Control Series S Bond are inconsistent with the provisions
relating to Pledged Bonds that are set forth in the New Mortgage, the provisions
of the New Mortgage shall apply.

         SECTION 3. Notwithstanding any provision in the Original Indenture,
this Supplemental Indenture No. 1, or the Pollution Control Series S Bonds to
the contrary, any payment by the Company under the New Mortgage of principal of,
or premium or interest on, the New Mortgage Pollution Control Series S Bonds
shall, to the extent thereof, be deemed to satisfy and discharge the obligation
of the Company to make any payment of principal, premium or interest, as the
case may be, in respect of the Pollution Control Series S Bonds which is then
due.

         SECTION 4. The Pollution Control Series S Bonds constitute "Pledged
Bonds" (as defined in the New Mortgage) and are subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, the Pollution Control Series S
Bonds shall be subject to surrender by the New Mortgage Trustee in accordance
with the provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Original Indenture, this Supplemental Indenture No. 1 or the
Pollution Control Series S Bonds are inconsistent with the provisions relating
to Pledged Bonds that are set forth in the New Mortgage, the provisions of the
New Mortgage shall apply.

                                   ARTICLE II.

                                   REDEMPTION.

         The Pollution Control Series S Bonds shall, subject to the provisions
of the Original Indentures, be redeemable on the same terms, on the same dates
and in the same manner as the New Mortgage Pollution Control Series S Bonds
shall be redeemed under the terms of the supplemental indenture no. 1 to the New
Mortgage dated as of March 1, 1998.

                                       -9-

<PAGE>   11




                                  ARTICLE III.

                           ISSUE OF POLLUTION CONTROL
                                 SERIES S BONDS.


         SECTION 1. The Company hereby exercises the right to obtain the
authentication of $18,700,000 principal amount of additional Bonds pursuant to
the terms of Section 6 of Article III of the Original Indenture in substitution
for refundable Bonds, all of which shall be Pollution Control Series S Bonds.

         SECTION 2. Such Pollution Control Series S Bonds may be authenticated
and delivered prior to the filing for recordation of this Supplemental Indenture
No. 1.

         SECTION 3. Notwithstanding any provision in the Original Indenture to
the contrary, execution of the Pollution Control Series S Bonds on behalf of the
Company, and the attesting of the corporate seal of the Company affixed to the
Pollution Control Series S Bonds by the officers of the Company authorized to do
such acts by Section 12 of Article II of the Original Indenture may be validly
done either by the manual or the facsimile signatures of such authorized
officers of the Company.


                                   ARTICLE IV.

                                  THE TRUSTEE.

         The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Original
Indenture set forth and upon the following terms and conditions:

         The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Supplemental Indenture No. 1 or
the due execution hereof by the Company or for or in respect of the recitals
contained herein, all of which recitals are made by the Company solely. In
general, each and every term and condition contained in Article XIII of the
Original Indenture shall apply to this Supplemental Indenture No. 1 with the
same force and effect as if the same were herein set forth in full, with such
omissions, variations and modifications thereof as may be appropriate to make
the same conform to this Supplemental Indenture No. 1.


                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

         This Supplemental Indenture No. 1 may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.


                                      -10-

<PAGE>   12




         IN WITNESS WHEREOF, Illinois Power Company has caused this Supplemental
Indenture No. 1 to be executed on its behalf by its Chairman and President, one
of its Executive Vice Presidents, one of its Senior Vice Presidents or one of
its Vice Presidents and its corporate seal to be hereto affixed and said seal
and this Supplemental Indenture No. 1 to be attested by its Secretary or one of
its Assistant Secretaries; and said Harris Trust and Savings Bank, in evidence
of its acceptance of the trust hereby created, has caused this Supplemental
Indenture No. 1 to be executed on its behalf by its President or one of its Vice
Presidents and its corporate seal to be hereto affixed and said seal and this
Supplemental Indenture No. 1 to be attested by its Secretary or one of its
Assistant Secretaries; all as of the first day of March, 1998.

                                                 ILLINOIS POWER COMPANY


                                                 By  /s/ Robert A. Schultz
                                                   -----------------------------
                                                     Robert A. Schultz
                                                     Vice President -- Finance


(CORPORATE SEAL)


ATTEST:

  /s/ Leah Manning Stetzner
- ---------------------------------------
Leah Manning Stetzner
Vice President, General Counsel
and Corporate Secretary

                                                 HARRIS TRUST AND SAVINGS BANK, 
                                                 Trustee


                                                 By /s/ J. Bartolini
                                                   -----------------------------
                                                       J. Bartolini
                                                       Vice President

(CORPORATE SEAL)

ATTEST:

  /s/ C. Potter
- ---------------------------------
C. Potter
Assistant Secretary

                                      -11-

<PAGE>   13




STATE OF ILLINOIS  )
COUNTY OF MACON    )  SS.



         BE IT REMEMBERED, that on this 2nd day of March, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President -- Finance and Leah Manning
Stetzner, Vice President, General Counsel and Corporate Secretary, of Illinois
Power Company, a corporation duly organized, incorporated and existing under the
laws of the State of Illinois, who are personally known to me to be such
officers, and who are personally known to me to be the same persons who executed
as such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such officers and as the free and voluntary act of
said Illinois Power Company for the uses and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                           -------------------------------------
                                           Notary Public, Macon County, Illinois


My Commission Expires on _________________.

(NOTARIAL SEAL)


STATE OF ILLINOIS )
                     SS.
COUNTY OF COOK    )  



         BE IT REMEMBERED, that on this 27th day of February, 1998, before me,
the undersigned Marianne Tinerella, a Notary Public within and for the County
and State aforesaid, personally came J. Bartolini, Vice President, and C.
Potter, Assistant Secretary, of Harris Trust and Savings Bank, a corporation
duly organized, incorporated and existing under the laws of the State of
Illinois, who are personally known to me to be the same persons who executed as
such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such Vice President and Secretary, respectively, and
as the free and voluntary act of said Harris Trust and Savings Bank for the uses
and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                            ------------------------------------
                                            Notary Public, Cook County, Illinois


My Commission Expires on May 21, 2001.
(NOTARIAL SEAL)


                                      -12-

<PAGE>   14




         Return To:                             This Instrument Was Prepared By:

         ILLINOIS POWER COMPANY                 Schiff Hardin & Waite
         Real Estate Dept. F-14                 7200 Sears Tower
         500 S. 27th Street                     Chicago, IL 60606
         Decatur, IL 62525





                                      -13-

<PAGE>   1
                                                                    EXHIBIT 4.40


================================================================================



                             ILLINOIS POWER COMPANY


                                       TO


                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE


                                  -------------



                          SUPPLEMENTAL INDENTURE NO. 2

                            DATED AS OF MARCH 1, 1998


                                       TO


                           MORTGAGE AND DEED OF TRUST

                             DATED NOVEMBER 1, 1943



================================================================================



<PAGE>   2
SUPPLEMENTAL INDENTURE No. 2 dated as of March 1, 1998 ("Supplemental Indenture
No. 2"), made by and between ILLINOIS POWER COMPANY, a corporation organized and
existing under the laws of the State of Illinois (the "Company"), party of the
first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the Mortgage and Deed of Trust dated November 1, 1943, hereinafter
mentioned, party of the second part;

      WHEREAS, the Company has heretofore executed and delivered its Mortgage
and Deed of Trust dated November 1, 1943 ("Original Indenture"), to the Trustee,
for the security of the First Mortgage Bonds of the Company issued and to be
issued thereunder (the "Bonds"); and

      WHEREAS, pursuant to the terms and provisions of the Original Indenture
there were created and authorized by Supplemental Indentures thereto bearing the
following dates, respectively, the First Mortgage Bonds of the series issued
thereunder and respectively identified opposite such dates:



<TABLE>
<CAPTION>
       DATE OF
     SUPPLEMENTAL            IDENTIFICATION
      INDENTURE                OF SERIES                      CALLED
     ------------            --------------                   ------
<S>                    <C>                        <C>                     
November 1, 1943       4% Series due 1973         Bonds of the 1973 Series
                             (redeemed)

March 1, 1946          2 7/8% Series due 1976     Bonds of the 1976 Series
                             (paid at
                             maturity)

February 1, 1948       3 1/2% Series due 1978     Bonds of the 1978 Series
                             (paid at
                             maturity)

July 1, 1949           2 7/8 % Series due 1979    Bonds of the 1979 Series
                             (paid at              
                             maturity)

April 1, 1950          2 3/4% Series due 1980     Bonds of the 1980 Series
                             (paid at
                             maturity)

March 1, 1952          3 1/2% Series due 1982     Bonds of the 1982 Series
                             (paid at
                             maturity)

November 1, 1953       3 1/2% Series due 1983     Bonds of the 1983 Series
                              (paid at
                             maturity)

July 1, 1956           3 3/4% Series due 1986     Bonds of the 1986 Series
                             (paid at
                             maturity)

</TABLE>

                                       -1-

<PAGE>   3
<TABLE>
<CAPTION>
       DATE OF
     SUPPLEMENTAL            IDENTIFICATION
      INDENTURE                OF SERIES                      CALLED
     ------------            --------------                   ------
<S>                    <C>                        <C>                     
May 1, 1958            4% Series due 1988         Bonds of the 1988 Series
                             (redeemed)

January 1, 1963        4 1/4% Series due 1993     Bonds of the 1993 Series
                             (paid at
                             maturity)

October 1, 1966        5.85% Series due 1996      Bonds of the 1996 Series
                             (paid at
                             maturity)

January 1, 1968        6 3/8% Series due 1998     Bonds of the First 1998
                             (redeemed)           Series

October 1, 1968        6 3/4% Series due October  Bonds of the Second 1998
                       1, 1998 (redeemed)         Series

October 1, 1969        8.35% Series due 1999      Bonds of the First 1999
                             (redeemed)           Series

November 1, 1970       9% Series due 2000         Bonds of the 2000 Series
                             (redeemed)

October 1, 1971        7.60% Series due 2001      Bonds of the 2001 Series
                             (redeemed)

June 1, 1973           7 5/8% Series due 2003     Bonds of the First 2003
                             (redeemed)           Series

May 1, 1974            Pollution Control          Bonds of the Pollution
                       Series A                   Control Series A

September 1, 1974      10 1/2% Series due 2004    Bonds of the First 2004
                             (redeemed)           Series

July 1, 1976           8 3/4% Series due 2006     Bonds of the 2006 Series
                             (redeemed)

May 1, 1977            Pollution Control          Bonds of Pollution Control
                       Series B                   Series B

November 1, 1977       8 1/4% Series due 2007     Bonds of the 2007 Series
                              (redeemed)

August 1, 1978         8 7/8% Series due 2008     Bonds of the 2008 Series
                             (redeemed)

July 1, 1979           9 7/8% Series due July 1,  Bonds of the Second 2004
                       2004                       Series
                             (redeemed)

</TABLE>

                                       -2-

<PAGE>   4

<TABLE>
<CAPTION>
       DATE OF
     SUPPLEMENTAL            IDENTIFICATION
      INDENTURE                OF SERIES                      CALLED
     ------------            --------------                   ------
<S>                    <C>                        <C>                     
July 31, 1980          11 3/8% Series due 1987    Bonds of the 1987 Series
                             (redeemed)

August 1, 1980         12 5/8% Series due 2010    Bonds of the 2010 Series
                             (redeemed)

July 1, 1982           14 1/2% Series due 1990    Bonds of the 1990 Series
                             (redeemed)

November 1, 1982       12% Series due 2012        Bonds of the 2012 Series
                             (redeemed)

December 15, 1983      Pollution Control          Bonds of the Pollution
                       Series C                   Control Series C
                             (redeemed)

May 15, 1984           Pollution Control          Bonds of the Pollution
                       Series D                   Control Series D
                             (redeemed)

March 1, 1985          Pollution Control          Bonds of the Pollution
                       Series E                   Control Series E
                             (redeemed)

February 1, 1986       10 1/2% Series due 2016    Bonds of the First 2016
                             (redeemed)           Series

July 1, 1986           9 7/8% Series due 2016     Bonds of the Second 2016
                             (redeemed)           Series

September 1, 1986      9 3/8% Series due 2016     Bonds of the Third 2016
                             (redeemed)           Series

February 1, 1987       Pollution Control          Bonds of the Pollution
                       Series F                   Control Series F
                             (redeemed)

February 1, 1987       Pollution Control          Bonds of the Pollution
                       Series G                   Control Series G
                             (redeemed)

February 1, 1987       Pollution Control          Bonds of the Pollution
                       Series H                   Control Series H
                             (redeemed)

July 1, 1987           Pollution Control          Bonds of the Pollution
                       Series I                   Control Series I

July 1, 1988           10% Series due 1998        Bonds of the Third 1998
                             (redeemed)           Series

</TABLE>

                                       -3-

<PAGE>   5

<TABLE>
<CAPTION>
       DATE OF
     SUPPLEMENTAL            IDENTIFICATION
      INDENTURE                OF SERIES                      CALLED
     ------------            --------------                   ------
<S>                    <C>                        <C>                     
July 1, 1991           Pollution Control          Bonds of the Pollution
                       Series J                   Control Series J

June 1, 1992           Pollution Control          Bonds of the Pollution
                       Series K                   Control Series K

June 1, 1992           Pollution Control          Bonds of the Pollution
                       Series L                   Control Series L

July 1, 1992           7.95% Series due 2004      Bonds of the Third 2004
                                                  Series

July 1, 1992           8 3/4% Series due 2021     Bonds of the 2021 Series

September 1, 1992      6 1/2% Series due 1999     Bonds of the 1999 Series

February 15, 1993      8% Series due 2023         Bonds of the 2023 Series

March 15, 1993         6 1/8% Series due 2000     Bonds of the 2000 Series

March 15, 1993         6 3/4% Series due 2005     Bonds of the 2005 Series

July 15, 1993          7 1/2% Series due 2025     Bonds of the 2025 Series

August 1, 1993         6 1/2% Series due 2003     Bonds of the Second 2003
                                                  Series

October 15, 1993       5 5/8% Series due 2000     Bonds of the Second 2000
                                                  Series

November 1, 1993       Pollution Control          Bonds of the Pollution
                       Series M                   Control Series M

November 1, 1993       Pollution Control          Bonds of the Pollution
                       Series N                   Control Series N

November 1, 1993       Pollution Control          Bonds of the Pollution
                       Series O                   Control Series O

April 1, 1997          Pollution Control          Bonds of the Pollution
                       Series P                   Control Series P

April 1, 1997          Pollution Control          Bonds of the Pollution
                       Series Q                   Control Series Q

April 1, 1997          Pollution Control          Bonds of the Pollution
                       Series R                   Control Series R

</TABLE>

                                       -4-

<PAGE>   6




and

      WHEREAS, the Company desires to create a new series of Bonds to be issued
under the Original Indenture, to be known as Pollution Control Series T Bonds
(the "Pollution Control Series T Bonds") and to issue additional Bonds under the
Original Indenture; and

      WHEREAS, the Pollution Control Series T Bonds, are to be issued to Harris
Trust and Savings Bank, as trustee (the "New Mortgage Trustee") under the
Company's General Mortgage Indenture and Deed of Trust dated as of November 1,
1992 (the "New Mortgage") and are to be owned and held by the New Mortgage
Trustee as "Pledged Bonds" (as defined in the New Mortgage) in accordance with
the terms of the New Mortgage; and

      WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Original
Indenture, and pursuant to appropriate resolutions of the Board of Directors,
has duly resolved and determined to make, execute and deliver to the Trustee a
Supplemental Indenture No. 2 in the form hereof for the purposes herein
provided; and

      WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture No. 2 a valid, binding and legal instrument have been
done, performed and fulfilled and the execution and delivery hereof have been in
all respects duly authorized;

      NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE No. 2 WITNESSETH:

      THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Original Indenture and of One Dollar to it duly paid by
the Trustee at or before the ensealing and delivery of these presents, the
receipt whereof is hereby acknowledged, hereby covenants and agrees to and with
the Trustee and its successors in the trust under the Original Indenture, for
the benefit of the New Trustee and any successor holder of the Bonds as follows:

                                   ARTICLE I.

               DESCRIPTION OF POLLUTION CONTROL SERIES T BONDS.

      SECTION 1. The Company hereby creates a new series of Bonds to be known as
"Pollution Control Series T Bonds." The Pollution Control Series T Bonds shall
be executed, authenticated and delivered in accordance with the provisions of,
and shall in all respects be subject to, all of the terms, conditions and
covenants of the Original Indenture, as supplemented and modified. The Pollution
Control Series T Bonds will be issued only to the New Mortgage Trustee as
security for a series of bonds being issued under the Company's New Mortgage and
the supplemental indenture No. 2 to the New Mortgage dated as of March 1, 1998
("New Mortgage Pollution Control Series T Bonds") and in the same principal
amount as the New Mortgage Pollution Control Series T Bonds.


                                       -5-

<PAGE>   7




      Pollution Control Series T Bonds shall be dated as provided in Section 6
of Article II of the Original Indenture. All Pollution Control Series T Bonds
shall mature on March 1, 2028 and shall bear interest at the rate of five and
four-tenths per cent (5.40%) per annum, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, until the principal sum
is paid in full. Any payment by the Company of principal of , or premium or
interest on, any Pollution Control Series T Bonds shall be applied by the New
Mortgage Trustee to the payment of any principal, premium or interest, as the
case may be, in respect of the New Mortgage Pollution Control Series T Bonds due
in accordance with the terms of the New Mortgage.

      SECTION 2. The Pollution Control Series T Bonds and the Trustee's
Certificate shall be substantially in the following forms respectively:



                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                         POLLUTION CONTROL SERIES T BOND

No. __________                                                     $33,755,000

      ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to Harris Trust and Savings Bank as
trustee (the "New Mortgage Trustee") under the Company's General Mortgage
Indenture and Deed of Trust dated as of November 1, 1992 (the "New Mortgage") or
its respective registered assigns, the principal sum of $33,755,000 on March 1,
2028, in any coin or currency of the United States of America which at the time
of payment is legal tender for public and private debts, and to pay interest in
like coin or currency from March 1, 1998, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, at the rate of five and
four-tenths percent (5.40%) per annum, until said principal sum is paid in full.
Both the principal of, and the interest on, this Bond are payable at the agency
of the Company in the City of Chicago, Illinois.

      This Bond shall not be entitled to any benefit under the Indenture or any
indenture supplemental thereto, or become valid or obligatory for any purpose,
until the form of certificate endorsed hereon shall have been signed by or on
behalf of Harris Trust and Savings Bank, the Trustee under the Indenture, or a
successor trustee thereto under the Indenture (the "Trustee").

      The provisions of this Bond are continued on the reverse hereof and such
continued provisions shall for all purposes have the same effect as though fully
set forth at this place.


                                       -6-

<PAGE>   8




      IN WITNESS WHEREOF, Illinois Power Company has caused this Bond to be
signed (manually or by facsimile signature) in its name by its President or a
Vice President, and its corporate seal (or a facsimile thereof) to be hereto
affixed and attested (manually or by facsimile signature) by its Secretary or an
Assistant Secretary.

Dated ______________, 1998                      ILLINOIS POWER COMPANY,


                                                By  . . . . . . . . . . . . .
                                                      Vice President

ATTEST:


 . . . . . . . . . . . . . .
      Assistant Secretary



                         [FORM OF TRUSTEE'S CERTIFICATE]

      This Bond is one of the Bonds of the series designated therein, described
in the within-mentioned Indenture and the Supplemental Indenture No. 2 dated as
of March 1, 1998.


                                          HARRIS TRUST AND SAVINGS BANK,
                                                                      Trustee,

                                          By . . . . . . . . . . . . . . . . .
                                                Authorized Officer

                            [FORM OF REVERSE OF BOND)

      This Bond is one of a duly authorized issue of Bonds of the Company (the
"Bonds") in unlimited aggregate principal amount, of the series hereinafter
specified, all issued and to be issued under and equally secured by the Mortgage
and Deed of Trust (the "Indenture"), dated November 1, 1943, executed by the
Company to Harris Trust and Savings Bank (the "Trustee"), as Trustee, to which
Indenture and all indentures supplemental thereto, including the Supplemental
Indenture dated February 15, 1993, which amended Section 1 of Article IX of the
Indenture, reference is hereby made for a description of the properties
mortgaged and pledged, the nature and extent of the security, the rights of the
registered owners of the Bonds and of the Trustee in respect thereof, and the
terms and conditions upon which the Bonds are, and are to be, secured. The Bonds
may be issued in series, for various principal sums, may mature at different
times, may bear interest at different rates and may otherwise vary as in the
Indenture provided. This Bond is one of a series designated as the "Pollution
Control Series T Bonds" (the "Pollution Control Series T Bonds") of the Company,
unlimited in aggregate principal amount, issued under and secured by the
Indenture and described in the supplemental indenture no. 2 dated as of March 1,



                                       -7-

<PAGE>   9




1998 ("Supplemental Indenture No. 2 of March 1, 1998"), between the Company and
the Trustee, supplemental to the Indenture.

      To the extent permitted by, and as provided in, the Indenture,
modifications or alterations of the Indenture, or of any indenture supplemental
thereto, and of the rights and obligations of the Company and of the holders of
the Bonds and coupons may be made with the consent of the Company by an
affirmative vote of the holders of not less than 662/3% in amount of the Bonds
entitled to vote then outstanding, at a meeting of Bondholders called and held
as provided in the Indenture, and by an affirmative vote of the holders of not
less than 662/3% in amount of the Bonds of any series entitled to vote then
outstanding and affected by such modification or alteration, in case one or more
but less than all of the series of Bonds then outstanding under the Indenture
are so affected; provided however, that no such modification or alteration shall
be made which will affect the terms of payment of the principal of, or interest
or premium, if any, on this Bond.

      This Pollution Control Series T Bond is subject to redemption in
accordance with the terms of Article II of the Supplemental Indenture No. 2 of
March 1, 1998.

      In case an Event of Default, as defined in the Indenture, shall occur, the
principal of all the Bonds at any such time outstanding under the Indenture may
be declared or may become due and payable, upon the conditions and in the manner
and with the effect provided in the Indenture. The Indenture provides that such
declaration may in certain events be rescinded by the holders of a majority in
principal amount of the Bonds outstanding.

      No recourse shall be had for the payment of the principal of, or premium
or interest on this Bond, or for any claim based hereon or on the Indenture or
any indenture supplemental thereto, against any incorporator, or against any
stockholder, director or officer, as such, past, present or future, of the
Company, or of any predecessor or successor corporation, either directly or
through the Company or any such predecessor or successor corporation, whether by
virtue of any constitution, statute or rule of law, or by the enforcement of any
assessment or penalty or otherwise, all such liability, whether at common law,
in equity, by any constitution, statute, rule of law, or otherwise, of
incorporators, stockholders, directors or officers being released by every owner
hereof by the acceptance of this Bond and as part of the consideration for the
issue hereof, and being likewise released by the terms of the Indenture;
provided, however, that nothing herein or in the Indenture or any indenture
supplemental thereto contained shall prevent the enforcement of the liability,
if any, of any stockholder or subscriber to capital stock upon or in respect of
shares of capital stock not fully paid up.

      Notwithstanding any provision in the Indenture, the Supplemental Indenture
No. 2 of March 1, 1998 or this Pollution Control Series T Bond to the contrary,
any payment by the Company under the New Mortgage of principal of, or premium or
interest on, bonds which shall have been authenticated and delivered under the
New Mortgage (the "New Mortgage Pollution Control Series T Bonds") upon the
basis of the issuance and delivery to the New Mortgage Trustee of the Pollution
Control



                                       -8-

<PAGE>   10




Series T Bonds shall, to the extent thereof, be deemed to satisfy and discharge
the obligation of the Company to make a payment of principal, premium or
interest, as the case may be, in respect of this Pollution Control Series T Bond
which is then due.

      This Pollution Control Series T Bond constitutes a "Pledged Bond" (as
defined in the New Mortgage) and is subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, this Pollution Control Series
T Bond shall be subject to surrender by the New Mortgage Trustee in accordance
with the provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Indenture, the Supplemental Indenture No. 2 of March 1, 1998
or this Pollution Control Series T Bond are inconsistent with the provisions
relating to Pledged Bonds that are set forth in the New Mortgage, the provisions
of the New Mortgage shall apply.

      SECTION 3. Notwithstanding any provision in the Original Indenture, this
Supplemental Indenture No. 2, or the Pollution Control Series T Bonds to the
contrary, any payment by the Company under the New Mortgage of principal of, or
premium or interest on, the New Mortgage Pollution Control Series T Bonds shall,
to the extent thereof, be deemed to satisfy and discharge the obligation of the
Company to make any payment of principal, premium or interest, as the case may
be, in respect of the Pollution Control Series T Bonds which is then due.

      SECTION 4. The Pollution Control Series T Bonds constitute "Pledged Bonds"
(as defined in the New Mortgage) and are subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, the Pollution Control Series T
Bonds shall be subject to surrender by the New Mortgage Trustee in accordance
with the provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Original Indenture, this Supplemental Indenture No. 2 or the
Pollution Control Series T Bonds are inconsistent with the provisions relating
to Pledged Bonds that are set forth in the New Mortgage, the provisions of the
New Mortgage shall apply.

                                   ARTICLE II.

                                   REDEMPTION.

      The Pollution Control Series T Bonds shall, subject to the provisions of
the Original Indentures, be redeemable on the same terms, on the same dates and
in the same manner as the New Mortgage Pollution Control Series T Bonds shall be
redeemed under the terms of the supplemental indenture No. 2 to the New Mortgage
dated as of March 1, 1998.

                                       -9-

<PAGE>   11




                                  ARTICLE III.

                           ISSUE OF POLLUTION CONTROL
                                 SERIES T BONDS.


      SECTION 1. The Company hereby exercises the right to obtain the
authentication of $33,755,000 principal amount of additional Bonds pursuant to
the terms of Section 6 of Article III of the Original Indenture in substitution
for refundable Bonds, all of which shall be Pollution Control Series T Bonds.

      SECTION 2. Such Pollution Control Series T Bonds may be authenticated and
delivered prior to the filing for recordation of this Supplemental Indenture No.
2.

      SECTION 3. Notwithstanding any provision in the Original Indenture to the
contrary, execution of the Pollution Control Series T Bonds on behalf of the
Company, and the attesting of the corporate seal of the Company affixed to the
Pollution Control Series T Bonds by the officers of the Company authorized to do
such acts by Section 12 of Article II of the Original Indenture may be validly
done either by the manual or the facsimile signatures of such authorized
officers of the Company.


                                   ARTICLE IV.

                                  THE TRUSTEE.

      The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Original
Indenture set forth and upon the following terms and conditions:

      The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Supplemental Indenture No. 2 or
the due execution hereof by the Company or for or in respect of the recitals
contained herein, all of which recitals are made by the Company solely. In
general, each and every term and condition contained in Article XIII of the
Original Indenture shall apply to this Supplemental Indenture No. 2 with the
same force and effect as if the same were herein set forth in full, with such
omissions, variations and modifications thereof as may be appropriate to make
the same conform to this Supplemental Indenture No. 2.


                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

      This Supplemental Indenture No. 2 may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.


                                      -10-

<PAGE>   12




      IN WITNESS WHEREOF, Illinois Power Company has caused this Supplemental
Indenture No. 2 to be executed on its behalf by its Chairman and President, one
of its Executive Vice Presidents, one of its Senior Vice Presidents or one of
its Vice Presidents and its corporate seal to be hereto affixed and said seal
and this Supplemental Indenture No. 2 to be attested by its Secretary or one of
its Assistant Secretaries; and said Harris Trust and Savings Bank, in evidence
of its acceptance of the trust hereby created, has caused this Supplemental
Indenture No. 2 to be executed on its behalf by its President or one of its Vice
Presidents and its corporate seal to be hereto affixed and said seal and this
Supplemental Indenture No. 2 to be attested by its Secretary or one of its
Assistant Secretaries; all as of the first day of March, 1998.

                                    ILLINOIS POWER COMPANY


                                    By  /s/ Robert A. Schultz
                                      ------------------------------------------
                                          Robert A. Schultz
                                          Vice President -- Finance


(CORPORATE SEAL)


ATTEST:

  /s/ Leah Manning Stetzner
- --------------------------------------
Leah Manning Stetzner
Vice President, General Counsel
and Corporate Secretary

                                    HARRIS TRUST AND SAVINGS BANK, Trustee


                                    By  /s/ J. Bartolini
                                      ------------------------------------------
                                          J. Bartolini
                                          Vice President

(CORPORATE SEAL)

ATTEST:

  /s/ C. Potter
- ---------------------------
C. Potter
Assistant Secretary

                                      -11-

<PAGE>   13




STATE OF ILLINOIS  )
                      SS.
COUNTY OF MACON    )

      BE IT REMEMBERED, that on this 2nd day of March, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President -- Finance and Leah Manning
Stetzner, Vice President, General Counsel and Corporate Secretary, of Illinois
Power Company, a corporation duly organized, incorporated and existing under the
laws of the State of Illinois, who are personally known to me to be such
officers, and who are personally known to me to be the same persons who executed
as such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such officers and as the free and voluntary act of
said Illinois Power Company for the uses and purposes therein set forth.

      IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                          --------------------------------------
                                          Notary Public, Macon County, Illinois
My Commission Expires on                  .
                         -----------------
(NOTARIAL SEAL)


STATE OF ILLINOIS )
                     SS.
COUNTY OF COOK    )

      BE IT REMEMBERED, that on this 27th day of February, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President, and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such Vice President and Secretary, respectively, and as the
free and voluntary act of said Harris Trust and Savings Bank for the uses and
purposes therein set forth.

      IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                         ---------------------------------------
                                          Notary Public, Cook County, Illinois



My Commission Expires on May 21, 2001.
(NOTARIAL SEAL)



                                      -12-


<PAGE>   14




      Return To:                          This Instrument Was Prepared By:

      ILLINOIS POWER COMPANY              Schiff Hardin & Waite
      Real Estate Dept. F-14              7200 Sears Tower
      500 S. 27th Street                  Chicago, IL 60606
      Decatur, IL 62525





                                      -13-

<PAGE>   1



                                                                   EXHIBIT 4.41




================================================================================



                             ILLINOIS POWER COMPANY
                                        
                                        
                                       TO
                                        
                                        
                         HARRIS TRUST AND SAVINGS BANK,
                                        
                                   AS TRUSTEE
                                        
                                        
                        ,____________________________
                                        
                                        
                                        
                          SUPPLEMENTAL INDENTURE NO. 1
                                        
                           DATED AS OF MARCH 1, 1998
                                        
                                        
                                       TO
                                        
                                        
                  GENERAL MORTGAGE INDENTURE AND DEED OF TRUST
                                        
                          DATED AS OF NOVEMBER 1, 1992
                                        
                                        
                                        
================================================================================
                                        
                                        
                                        
<PAGE>   2



SUPPLEMENTAL INDENTURE No. 1 dated as of March 1, 1998 ("Supplemental Indenture
No. 1"), made by and between ILLINOIS POWER COMPANY, a corporation organized and
existing under the laws of the State of Illinois (the "Company"), party of the
first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the General Mortgage Indenture and Deed of Trust dated as of November 1,
1992, hereinafter mentioned, party of the second part;

     WHEREAS, the Illinois Environmental Facilities Financing Act (20 ILCS
3515/1 et seq.), as amended and supplemented (the "Act"), authorizes and
empowers the Illinois Development Finance Authority, a political subdivision and
body politic and corporate, duly organized and validly existing under and by
virtue of the Constitution and laws of the State of Illinois ("IDFA") to issue
bonds for the refunding of any bonds deemed necessary in connection with any
purpose of IDFA; and

     WHEREAS, pursuant to and in accordance with the provisions of the Act, a
predecessor of IDFA has heretofore made a loan to the Company for the purpose of
financing certain pollution control facilities of the Company; and

     WHEREAS, such predecessor to IDFA has financed a portion of the costs of
such pollution control facilities as an authorized project under the Act by the
issuance of the Illinois Industrial Pollution Control Financing Authority
Pollution Control Revenue Bonds, 1977 Series A (Illinois Power Company Project)
in the aggregate principal amount of $18,700,000 (all of which are currently
outstanding) (the "Prior Bonds") and by loaning the proceeds therefrom to the
Company; and

     WHEREAS, IDFA now intends to issue its Pollution Control Revenue Refunding
Bonds, 1998 Series A (Illinois Power Company Project) in the aggregate principal
amount of $18,700,000 (the "Series A IDFA Bonds") and to loan the proceeds
therefrom to the Company pursuant to a Loan Agreement dated as of March 1, 1998
(the "Loan Agreement") to assist the Company in refunding on or about April 1,
1998 the Prior Bonds; and

     WHEREAS, the Series A IDFA Bonds will be issued by IDFA pursuant to an
Indenture of Trust (as from time to time amended or modified, the "IDFA Series A
Indenture") dated as of March 1, 1998 between IDFA and Harris Trust and Savings
Bank, as Trustee under such Indenture (together with any successor in such
capacity the "IDFA Indenture Trustee");

     WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 as from time
to time amended (the "Indenture"), to the Trustee, for the security of the Bonds
of the Company issued and to be issued thereunder (the "Bonds"); and

     WHEREAS, pursuant to the terms and provisions of the Indenture there were
created and authorized by supplemental indentures thereto bearing the following
dates, respectively, the New Mortgage Bonds of the series issued thereunder and
respectively identified opposite such dates:







<PAGE>   3



<TABLE>
<CAPTION>
       DATE OF
SUPPLEMENTAL INDENTURE       IDENTIFICATION OF SERIES                    CALLED
- ----------------------       ------------------------                    ------             
<S>                        <C>                             <C>
February 15, 1993            8% Series due 2023              Bonds of the 2023 Series

March 15, 1993               6 1/8% Series due 2000          Bonds of the 2000 Series

March 15, 1993               6 3/4% Series due 2005          Bonds of the 2005 Series

July 15, 1993                7 1/2% Series due 2025          Bonds of the 2025 Series

August 1, 1993               6 1/2% Series due 2003          Bonds of the 2003 Series

October 15, 1993             5 5/8% Series due 2000          Bonds of the Second 2000       
                                                             Series
                                                                                           
November 1, 1993             Pollution Control Series        Bonds of the Pollution Control
                             M                               Series M
                                                                                           
November 1, 1993             Pollution Control Series        Bonds of the Pollution Control
                             N                               Series N
                                                                                           
November 1, 1993             Pollution Control Series        Bonds of the Pollution Control
                             O                               Series O
                                                                                           
April 1, 1997                Pollution Control Series        Bonds of the Pollution Control
                             P                               Series P
                                                                                           
April 1, 1997                Pollution Control Series        Bonds of the Pollution Control
                             Q                               Series Q
                                                                                           
April 1, 1997                Pollution Control Series        Bonds of the Pollution Control
                             R                               Series R
</TABLE>

and

     WHEREAS, the Company desires to create a new series of Bonds to be issued
under the Indenture to be known as New Mortgage Bonds, Pollution Control Series
S (the "Pollution Control Series S Bonds"); and

     WHEREAS, the Company, in the exercise of the powers and authority conferred
upon and reserved to it under the provisions of the Indenture, and pursuant to
appropriate resolutions of the Board of Directors, has duly resolved and
determined to make, execute and deliver to the Trustee a Supplemental Indenture
No. 1 in the form hereof for the purposes herein provided; and

     WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture No. 1 a valid, binding and legal instrument have been
done, performed and fulfilled and the execution and delivery hereof have been in
all respects duly authorized;

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE No. 1 WITNESSETH:



                                      -2-



<PAGE>   4



     THAT Illinois Power Company, in consideration of the purchase and ownership
from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of One Dollar to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, hereby covenants and agrees to and with the Trustee and
its successors in the trust under the Indenture, for the benefit of those who
shall hold the Bonds as follows:

                                   ARTICLE I.

                DESCRIPTION OF POLLUTION CONTROL SERIES S BONDS.

     SECTION 1. The Company hereby creates a new series of Bonds to be known as
"Pollution Control Series S Bonds." The Pollution Control Series S Bonds shall
be executed, authenticated and delivered in accordance with the provisions of,
and shall in all respects be subject to, all of the terms, conditions and
covenants of the Indenture, as supplemented and modified.  The Pollution Control
Series S Bonds shall be issued only to the IDFA Indenture Trustee as security
for the Company's obligations under the Loan Agreement relating to the Series A
IDFA Bonds.  The Company shall not cause any Pollution Control Series S Bonds to
be paid or deemed to be paid prior to the payment of the Series A IDFA Bonds.

     The Pollution Control Series S Bonds shall be dated as provided in Section
3.03 of Article Three of the Indenture.  The Pollution Control Series S Bonds
shall mature on March 1, 2028, and shall bear interest at the rate of five and
four-tenths per cent (5.40%) per annum, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, until the principal sum
is paid in full.

     SECTION 2. The Pollution Control Series S Bonds and the Trustee's
Certificate of Authentication shall be substantially in the following forms
respectively:

                             [FORM OF FACE OF BOND)
                                        
                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)
                                        
                 NEW MORTGAGE BOND, POLLUTION CONTROL SERIES S

No. ________                                                         $18,700,000

     ILLINOIS POWER COMPANY, a corporation organized and existing under the laws
of the State of Illinois (the "Company"), which term shall include any successor
corporation as defined in the Indenture hereinafter referred to), for value
received, hereby promises to pay to Harris Trust and Savings Bank, as Trustee
(the "IDFA Indenture Trustee") under the Indenture of Trust dated as of March 1,
1998 (the "IDFA Series A Indenture"), relating to the Pollution Control Revenue
Refunding Bonds, 1998 Series A (the "Series A IDFA Bonds"), between the Illinois
Development Finance Authority ("IDFA") and the IDFA Indenture Trustee, or
registered assigns, the principal sum of $18,700,000 on March 1, 2028, in any 




                                      -3-



<PAGE>   5




coin or currency of the United States of America which at the time of payment is
legal tender for public and private debts, and to pay interest thereon in like
coin or currency from March 1, 1998, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, at the rate of five and
four-tenths per cent (5.40%) per annum, until said principal sum is paid in
full.  Both the principal of, and the interest on, this Bond are payable at the
agency of the Company in the City of Chicago, Illinois.

     This Bond shall not be entitled to any benefit under the Indenture or any
indenture supplemental thereto, or become valid or obligatory for any purpose,
until the form of certificate endorsed hereon shall have been signed by or on
behalf of Harris Trust and Savings Bank, the Trustee under the Indenture, or a
successor trustee thereto under the Indenture (the "Trustee").

     The provisions of this Bond are continued on the reverse hereof and such
continued provisions shall for all purposes have the same effect as though fully
set forth at this place.

     IN WITNESS WHEREOF, Illinois Power Company has caused this Bond to be
signed (manually or by facsimile signature) in its name by an Authorized
Executive Officer, as defined in the aforesaid Indenture, and its corporate seal
(or a facsimile thereof) to be hereto affixed and attested (manually or by
facsimile signature) by an Authorized Executive Officer, as defined in such
Indenture on the date hereof.

Dated __________, 1998               ILLINOIS POWER COMPANY,


                                     By . . . . . . . . . . . . . . . . .
                                           Authorized Executive Officer

ATTEST:


 . . . . . . . . . . . . . . . . . .
    Authorized Executive Officer


               [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

     This is one of the Bonds of the series designated therein referred to in
the within-mentioned Indenture and the Supplemental Indenture No. 1 dated as of
March 1, 1998.

                                     HARRIS TRUST AND SAVINGS BANK,
                                                             Trustee,

                                     By . . . . . . . . . . . . . . . . .
                                            Authorized Signatory




                                      -4-



<PAGE>   6




                           [FORM OF REVERSE OF BOND]

     This Bond is one of a duly authorized issue of Bonds of the Company (the
"Bonds") in unlimited aggregate principal amount, of the series hereinafter
specified, all issued and to be issued under and equally secured by the General
Mortgage Indenture and Deed of Trust (the "Indenture"), dated as of November 1,
1992, executed by the Company to Harris Trust and Savings Bank (the "Trustee"),
as Trustee, to which Indenture and all indentures supplemental thereto reference
is hereby made for a description of the properties mortgaged and pledged, the
nature and extent of the security, the rights of registered owners of the Bonds
and of the Trustee in respect thereof, and the terms and conditions upon which
the Bonds are, and are to be, secured. The Bonds may be issued in series, for
various principal sums, may mature at different times, may bear interest at
different rates and may otherwise vary as provided in the Indenture. This Bond
is one of a series designated as the "New Mortgage Bonds, Pollution Control
Series S" (the "Pollution Control Series S Bonds") of the Company, unlimited in
aggregate principal amount, issued under and secured by the Indenture and
described in the supplemental indenture no. 1 dated as of March 1, 1998 (the
"Supplemental Indenture No. 1 of March 1, 1998"), between the Company and the
Trustee, supplemental to the Indenture.

     This Pollution Control Series S Bond is subject to redemption in accordance
with the terms of Article II of the Supplemental Indenture No. 1 of March 1,
1998.

     In case an Event of Default, as defined in the Indenture, shall occur, the
principal of all Bonds at any such time outstanding under the Indenture may be
declared or may become due and payable, upon the conditions and in the manner
and with the effect provided in the Indenture. The Indenture provides that such
declaration may be rescinded under certain circumstances.

                                  ARTICLE II.

                                  REDEMPTION.

     SECTION 1.  The Pollution Control Series S Bonds shall, subject to the
provisions of the Indenture, be redeemable on the same terms, on the same dates
and in the same manner as the Series A IDFA Bonds shall be redeemed under the
terms of the IDFA Series A Indenture.

     SECTION 2.  The Pollution Control Series S Bonds shall be redeemed in whole
whenever the Trustee receives a written notice from the IDFA Indenture Trustee
stating that the principal of any bonds then outstanding under the IDFA Series A
Indenture has been declared to be immediately due and payable pursuant to the
provisions of Section 802 thereof.  Such redemption shall be on any date not
more than  one (1) business day after the receipt of such notice from the
trustee under the IDFA Series A Indenture.  Any such redemption shall be at the
redemption price of 100% of the principal amount of the Bonds to be redeemed,
together with accrued interest to the date selected for redemption.  A demand
from the IDFA Indenture Trustee shall be executed on behalf of such IDFA
Indenture Trustee by its President or a Vice President or a Trust Officer and



                                      -5-



<PAGE>   7



shall be deemed received by the Trustee when delivered at its corporate trust
office in Chicago, Illinois.  The Trustee may conclusively rely as to the truth
of the statements contained therein upon any such demand.

     SECTION 3.  Subject to the provisions of the Indenture, notice of
redemption of Pollution Control Series S Bonds shall be sent by the Company by
certified mail, postage prepaid, not later than the date fixed for redemption to
the registered owners of such Bonds at their addresses as the same shall appear,
if at all, on the transfer register of the Company.  Any notice which is mailed
in the manner herein provided shall be conclusively presumed to have been duly
given whether or not the holders receive such notice, but failure to give notice
by mail, or any defect in such notice, to the holder of any such Bonds
designated for redemption shall not affect the validity of the redemption of any
other such Bond.

                                  ARTICLE III.

                           ISSUE OF POLLUTION CONTROL
                                SERIES S BONDS.

     SECTION 1.  The Company hereby exercises the right to obtain the
authentication of $18,700,000 principal amount of additional Bonds pursuant to
the terms of Section 4.02 of the Indenture, all of which shall be Pollution
Control Series S Bonds.

     SECTION 2.  Such Pollution Control Series S Bonds may be authenticated and
delivered prior to the filing for recordation of this Supplemental Indenture No.
1.

                                  ARTICLE IV.

                                  THE TRUSTEE.

     The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:

     The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Supplemental Indenture No. 1 or
the due execution hereof by the Company or for or in respect of the recitals
contained herein, all of which recitals are made by the Company solely.  In
general, each and every term and condition contained in Article Eleven of the
Indenture shall apply to this Supplemental Indenture No. 1 with the same force
and effect as if the same were herein set forth in full, with such omissions,
variations and modifications thereof as may be appropriate to make the same
conform to this Supplemental Indenture No. 1.




                                      -6-



<PAGE>   8



                                   ARTICLE V.

                           MISCELLANEOUS PROVISIONS.

     This Supplemental Indenture No. 1 may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.




                                      -7-

<PAGE>   9



     IN WITNESS WHEREOF, said Illinois Power Company has caused this
Supplemental Indenture No. 1 to be executed on its behalf by an Authorized
Executive Officer as defined in the Indenture, and its corporate seal to be
hereto affixed and said seal and this Supplemental Indenture No. 1 to be
attested by an Authorized Executive Officer as defined in the Indenture; and
said Harris Trust and Savings Bank, in evidence of its acceptance of the trust
hereby created, has caused this Supplemental Indenture No. 1 to be executed on
its behalf by its President or one of its Vice Presidents and its corporate seal
to be hereto affixed and said seal and this Supplemental Indenture No. 1 to be
attested by its Secretary or one of its Assistant Secretaries; all as of the
first day of March, 1998.

                                      ILLINOIS POWER COMPANY


                                      By   /s/ Robert A. Schultz
                                         -------------------------------------  
                                             Robert A. Schultz
                                             Vice President -- Finance


(CORPORATE SEAL)

ATTEST:

  /s/ Leah Manning Stetzner
- -------------------------------
Leah Manning Stetzner
Vice President, General Counsel
and Corporate Secretary

                                      HARRIS TRUST AND SAVINGS BANK, Trustee


                                      By   /s/ J. Bartolini
                                         -------------------------------------  
                                             J. Bartolini
                                             Vice President
(CORPORATE SEAL)


ATTEST:

  /s/ C. Potter
- ----------------------------
C. Potter
Assistant Secretary



                                      -8-


<PAGE>   10



STATE OF ILLINOIS )  SS.
COUNTY OF MACON   )

     BE IT REMEMBERED, that on this 2nd day of March, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President -- Finance and Leah Manning
Stetzner, Vice President, General Counsel and Corporate Secretary, of Illinois
Power Company, a corporation duly organized, incorporated and existing under the
laws of the State of Illinois, who are personally known to me to be such
officers, and who are personally known to me to be the same persons who executed
as such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such officers and as the free and voluntary act of
said Illinois Power Company for the uses and purposes therein set forth.

     IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.

                                    ____________________________________________
                                           Notary Public, Macon County, Illinois

My Commission Expires on ___________________.

(NOTARIAL SEAL)


STATE OF ILLINOIS )  SS.
COUNTY OF COOK    )

     BE IT REMEMBERED, that on 27th day of February, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such Vice President and Assistant Secretary, and as the free
and voluntary act of said Harris Trust and Savings Bank for the uses and
purposes therein set forth.

     IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.


                                    ____________________________________________
                                            Notary Public, Cook County, Illinois

My Commission Expires on May 21, 2001.
(NOTARIAL SEAL)



                                      -9-


<PAGE>   11


Return To:                               This Instrument Was Prepared By:

      ILLINOIS POWER COMPANY             Schiff Hardin & Waite
      Real Estate Dept. F-14             7200 Sears Tower
      500 S. 27th Street                 Chicago, IL 60606
      Decatur, IL 62525





                                      -10-

<PAGE>   1
                                                                    EXHIBIT 4.42


================================================================================



                             ILLINOIS POWER COMPANY


                                       TO


                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE


                                  -------------



                          SUPPLEMENTAL INDENTURE NO. 2

                            DATED AS OF MARCH 1, 1998


                                       TO


                  GENERAL MORTGAGE INDENTURE AND DEED OF TRUST

                          DATED AS OF NOVEMBER 1, 1992



================================================================================



<PAGE>   2




SUPPLEMENTAL INDENTURE No. 2 dated as of March 1, 1998 ("Supplemental Indenture
No. 2"), made by and between ILLINOIS POWER COMPANY, a corporation organized and
existing under the laws of the State of Illinois (the "Company"), party of the
first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the General Mortgage Indenture and Deed of Trust dated as of November 1,
1992, hereinafter mentioned, party of the second part;

      WHEREAS, the Illinois Environmental Facilities Financing Act (20 ILCS
3515/1 et seq.), as amended and supplemented (the "Act"), authorizes and
empowers the Illinois Development Finance Authority, a political subdivision and
body politic and corporate, duly organized and validly existing under and by
virtue of the Constitution and laws of the State of Illinois ("IDFA") to issue
bonds for the refunding of any bonds deemed necessary in connection with any
purpose of IDFA; and

      WHEREAS, pursuant to and in accordance with the provisions of the Act,
IDFA has heretofore made a loan to the Company for the purpose of financing
certain pollution control facilities of the Company; and

      WHEREAS, IDFA has financed a portion of the costs of such pollution
control facilities as an authorized project under the Act by the issuance of the
Illinois Industrial Pollution Control Financing Authority Pollution Control
Revenue Bonds, 1987 Series A (Illinois Power Company Project) in the aggregate
principal amount of $33,755,000 (all of which are currently outstanding) (the
"Prior Bonds") and by loaning the proceeds therefrom to the Company; and

      WHEREAS, IDFA now intends to issue its Pollution Control Revenue Refunding
Bonds, 1998 Series B (Illinois Power Company Project) in the aggregate principal
amount of $33,755,000 (the "Series B IDFA Bonds") and to loan the proceeds
therefrom to the Company pursuant to a Loan Agreement dated as of March 1, 1998
(the "Loan Agreement") to assist the Company in refunding on or about April 1,
1998 the Prior Bonds; and

      WHEREAS, the Series B IDFA Bonds will be issued by IDFA pursuant to an
Indenture of Trust (as from time to time amended or modified, the "IDFA Series B
Indenture") dated as of March 1, 1998 between IDFA and Harris Trust and Savings
Bank, as Trustee under such Indenture (together with any successor in such
capacity the "IDFA Indenture Trustee");

      WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 as from time
to time amended (the "Indenture"), to the Trustee, for the security of the Bonds
of the Company issued and to be issued thereunder (the "Bonds"); and

      WHEREAS, pursuant to the terms and provisions of the Indenture there were
created and authorized by supplemental indentures thereto bearing the following
dates, respectively, the New Mortgage Bonds of the series issued thereunder and
respectively identified opposite such dates:


<PAGE>   3





<TABLE>
<CAPTION>
  SUPPLEMENTAL INDENTURE   IDENTIFICATION OF SERIES             CALLED
  ----------------------   ------------------------             ------
<S>                        <C>                        <C>        
February 15, 1993          8% Series due 2023         Bonds of the 2023 Series

March 15, 1993             6 1/8% Series due 2000     Bonds of the 2000 Series

March 15, 1993             6 3/4% Series due 2005     Bonds of the 2005 Series

July 15, 1993              7 1/2% Series due 2025     Bonds of the 2025 Series

August 1, 1993             6 1/2% Series due 2003     Bonds of the 2003 Series

October 15, 1993           5 5/8% Series due 2000     Bonds of the Second 2000
                                                      Series

November 1, 1993           Pollution Control Series   Bonds of the Pollution
                           M                          Control Series M

November 1, 1993           Pollution Control Series   Bonds of the Pollution
                           N                          Control Series N

November 1, 1993           Pollution Control Series   Bonds of the Pollution
                           O                          Control Series O

April 1, 1997              Pollution Control Series   Bonds of the Pollution
                           P                          Control Series P

April 1, 1997              Pollution Control Series   Bonds of the Pollution
                           Q                          Control Series Q

April 1, 1997              Pollution Control Series   Bonds of the Pollution
                           R                          Control Series R
</TABLE>

and

      WHEREAS, the Company desires to create a new series of Bonds to be issued
under the Indenture to be known as New Mortgage Bonds, Pollution Control Series
T (the "Pollution Control Series T Bonds"); and

      WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Indenture, and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and determined to make, execute and deliver to the Trustee a Supplemental
Indenture No. 2 in the form hereof for the purposes herein provided; and

      WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture No. 2 a valid, binding and legal instrument have been
done, performed and fulfilled and the execution and delivery hereof have been in
all respects duly authorized;

      NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE No. 2 WITNESSETH:


                                     -2-

<PAGE>   4




      THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of One Dollar to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, hereby covenants and agrees to and with the Trustee and
its successors in the trust under the Indenture, for the benefit of those who
shall hold the Bonds as follows:

                                   ARTICLE I.

               DESCRIPTION OF POLLUTION CONTROL SERIES T BONDS.

      SECTION 1. The Company hereby creates a new series of Bonds to be known as
"Pollution Control Series T Bonds." The Pollution Control Series T Bonds shall
be executed, authenticated and delivered in accordance with the provisions of,
and shall in all respects be subject to, all of the terms, conditions and
covenants of the Indenture, as supplemented and modified. The Pollution Control
Series T Bonds shall be issued only to the IDFA Indenture Trustee as security
for the Company's obligations under the Loan Agreement relating to the Series B
IDFA Bonds. The Company shall not cause any Pollution Control Series T Bonds to
be paid or deemed to be paid prior to the payment of the Series B IDFA Bonds.

      The Pollution Control Series T Bonds shall be dated as provided in Section
3.03 of Article Three of the Indenture. The Pollution Control Series T Bonds
shall mature on March 1, 2028, and shall bear interest at the rate of five and
four-tenths per cent (5.40%) per annum, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, until the principal sum
is paid in full.

      SECTION 2. The Pollution Control Series T Bonds and the Trustee's
Certificate of Authentication shall be substantially in the following forms
respectively:

                             [FORM OF FACE OF BOND)

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                NEW MORTGAGE BOND, POLLUTION CONTROL SERIES T

No. ________                                                       $33,755,000

      ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company"), which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to Harris Trust and Savings Bank, as
Trustee (the "IDFA Indenture Trustee") under the Indenture of Trust dated as of
March 1, 1998 (the "IDFA Series B Indenture"), relating to the Pollution Control
Revenue Refunding Bonds, 1998 Series B (the "Series B IDFA Bonds"), between the
Illinois Development Finance Authority ("IDFA") and the IDFA Indenture Trustee,
or registered assigns, the principal sum of $33,755,000 on March 1, 2028, in any



                                     -3-

<PAGE>   5




coin or currency of the United States of America which at the time of payment is
legal tender for public and private debts, and to pay interest thereon in like
coin or currency from March 1, 1998, payable semi-annually on March 1 and
September 1 of each year, commencing September 1, 1998, at the rate of five and
four-tenths per cent (5.40%) per annum, until said principal sum is paid in
full. Both the principal of, and the interest on, this Bond are payable at the
agency of the Company in the City of Chicago, Illinois.

      This Bond shall not be entitled to any benefit under the Indenture or any
indenture supplemental thereto, or become valid or obligatory for any purpose,
until the form of certificate endorsed hereon shall have been signed by or on
behalf of Harris Trust and Savings Bank, the Trustee under the Indenture, or a
successor trustee thereto under the Indenture (the "Trustee").

      The provisions of this Bond are continued on the reverse hereof and such
continued provisions shall for all purposes have the same effect as though fully
set forth at this place.

      IN WITNESS WHEREOF, Illinois Power Company has caused this Bond to be
signed (manually or by facsimile signature) in its name by an Authorized
Executive Officer, as defined in the aforesaid Indenture, and its corporate seal
(or a facsimile thereof) to be hereto affixed and attested (manually or by
facsimile signature) by an Authorized Executive Officer, as defined in such
Indenture on the date hereof.

Dated __________, 1998                    ILLINOIS POWER COMPANY,


                                          By . . . . . . . . . . . . . . . . .
                                                Authorized Executive Officer

ATTEST:


 . . . . . . . . . . . . . . . . . .
      Authorized Executive Officer

              [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

      This is one of the Bonds of the series designated therein referred to in
the within-mentioned Indenture and the Supplemental Indenture No. 2 dated as of
March 1, 1998.

                                          HARRIS TRUST AND SAVINGS BANK,
                                                                        Trustee,

                                          By . . . . . . . . . . . . . . . . .
                                                Authorized Signatory


                                     -4-

<PAGE>   6




                            [FORM OF REVERSE OF BOND]

      This Bond is one of a duly authorized issue of Bonds of the Company (the
"Bonds") in unlimited aggregate principal amount, of the series hereinafter
specified, all issued and to be issued under and equally secured by the General
Mortgage Indenture and Deed of Trust (the "Indenture"), dated as of November 1,
1992, executed by the Company to Harris Trust and Savings Bank (the "Trustee"),
as Trustee, to which Indenture and all indentures supplemental thereto reference
is hereby made for a description of the properties mortgaged and pledged, the
nature and extent of the security, the rights of registered owners of the Bonds
and of the Trustee in respect thereof, and the terms and conditions upon which
the Bonds are, and are to be, secured. The Bonds may be issued in series, for
various principal sums, may mature at different times, may bear interest at
different rates and may otherwise vary as provided in the Indenture. This Bond
is one of a series designated as the "New Mortgage Bonds, Pollution Control
Series T" (the "Pollution Control Series T Bonds") of the Company, unlimited in
aggregate principal amount, issued under and secured by the Indenture and
described in the supplemental indenture No. 2 dated as of March 1, 1998 (the
"Supplemental Indenture No. 2 of March 1, 1998"), between the Company and the
Trustee, supplemental to the Indenture.

      This Pollution Control Series T Bond is subject to redemption in
accordance with the terms of Article II of the Supplemental Indenture No. 2 of
March 1, 1998.

      In case an Event of Default, as defined in the Indenture, shall occur, the
principal of all Bonds at any such time outstanding under the Indenture may be
declared or may become due and payable, upon the conditions and in the manner
and with the effect provided in the Indenture. The Indenture provides that such
declaration may be rescinded under certain circumstances.

                                   ARTICLE II.

                                   REDEMPTION.

      SECTION 1. The Pollution Control Series T Bonds shall, subject to the
provisions of the Indenture, be redeemable on the same terms, on the same dates
and in the same manner as the Series B IDFA Bonds shall be redeemed under the
terms of the IDFA Series B Indenture.

      SECTION 2. The Pollution Control Series T Bonds shall be redeemed in whole
whenever the Trustee receives a written notice from the IDFA Indenture Trustee
stating that the principal of any bonds then outstanding under the IDFA Series B
Indenture has been declared to be immediately due and payable pursuant to the
provisions of Section 802 thereof. Such redemption shall be on any date not more
than one (1) business day after the receipt of such notice from the trustee
under the IDFA Series B Indenture. Any such redemption shall be at the
redemption price of 100% of the principal amount of the Bonds to be redeemed,
together with accrued interest to the date selected for redemption. A demand
from the IDFA Indenture Trustee shall be executed on behalf of such IDFA
Indenture Trustee by its President or a Vice President or a Trust Officer and
shall be deemed received

                                     -5-

<PAGE>   7




by the Trustee when delivered at its corporate trust office in Chicago,
Illinois. The Trustee may conclusively rely as to the truth of the statements
contained therein upon any such demand.

      SECTION 3. Subject to the provisions of the Indenture, notice of
redemption of Pollution Control Series T Bonds shall be sent by the Company by
certified mail, postage prepaid, not later than the date fixed for redemption to
the registered owners of such Bonds at their addresses as the same shall appear,
if at all, on the transfer register of the Company. Any notice which is mailed
in the manner herein provided shall be conclusively presumed to have been duly
given whether or not the holders receive such notice, but failure to give notice
by mail, or any defect in such notice, to the holder of any such Bonds
designated for redemption shall not affect the validity of the redemption of any
other such Bond.

                                  ARTICLE III.

                           ISSUE OF POLLUTION CONTROL
                                 SERIES T BONDS.

      SECTION 1. The Company hereby exercises the right to obtain the
authentication of $33,755,000 principal amount of additional Bonds pursuant to
the terms of Section 4.02 of the Indenture, all of which shall be Pollution
Control Series T Bonds.

      SECTION 2. Such Pollution Control Series T Bonds may be authenticated and
delivered prior to the filing for recordation of this Supplemental Indenture No.
2.

                                   ARTICLE IV.

                                  THE TRUSTEE.

      The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:

      The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Supplemental Indenture No. 2 or
the due execution hereof by the Company or for or in respect of the recitals
contained herein, all of which recitals are made by the Company solely. In
general, each and every term and condition contained in Article Eleven of the
Indenture shall apply to this Supplemental Indenture No. 2 with the same force
and effect as if the same were herein set forth in full, with such omissions,
variations and modifications thereof as may be appropriate to make the same
conform to this Supplemental Indenture No. 2.




                                     -6-

<PAGE>   8




                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

      This Supplemental Indenture No. 2 may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.


                                     -7-

<PAGE>   9




      IN WITNESS WHEREOF, said Illinois Power Company has caused this
Supplemental Indenture No. 2 to be executed on its behalf by an Authorized
Executive Officer as defined in the Indenture, and its corporate seal to be
hereto affixed and said seal and this Supplemental Indenture No. 2 to be
attested by an Authorized Executive Officer as defined in the Indenture; and
said Harris Trust and Savings Bank, in evidence of its acceptance of the trust
hereby created, has caused this Supplemental Indenture No. 2 to be executed on
its behalf by its President or one of its Vice Presidents and its corporate seal
to be hereto affixed and said seal and this Supplemental Indenture No. 2 to be
attested by its Secretary or one of its Assistant Secretaries; all as of the
first day of March, 1998.

                                    ILLINOIS POWER COMPANY


                                    By  /s/ Robert A. Schultz
                                      ------------------------------------------
                                          Robert A. Schultz
                                          Vice President -- Finance


(CORPORATE SEAL)

ATTEST:

  /s/ Leah Manning Stetzner
- -------------------------------
Leah Manning Stetzner
Vice President, General Counsel
and Corporate Secretary



                                          HARRIS TRUST AND SAVINGS BANK, Trustee



                                    By  /s/ J. Bartolini
                                      ------------------------------------------
                                          J. Bartolini
                                          Vice President
(CORPORATE SEAL)


ATTEST:


  /s/ C. Potter
- -------------------------------
C. Potter
Assistant Secretary


                                     -8-

<PAGE>   10




STATE OF ILLINOIS)
                       SS.

COUNTY OF MACON  )

      BE IT REMEMBERED, that on this 2nd day of March, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President -- Finance and Leah Manning
Stetzner, Vice President, General Counsel and Corporate Secretary, of Illinois
Power Company, a corporation duly organized, incorporated and existing under the
laws of the State of Illinois, who are personally known to me to be such
officers, and who are personally known to me to be the same persons who executed
as such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such officers and as the free and voluntary act of
said Illinois Power Company for the uses and purposes therein set forth.

      IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.


                                          --------------------------------------
                                          Notary Public, Macon County, Illinois



My Commission Expires on                  .
                         -----------------
(NOTARIAL SEAL)


STATE OF ILLINOIS  )
                      SS.
COUNTY OF COOK     )

      BE IT REMEMBERED, that on 27th day of February, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such Vice President and Assistant Secretary, and as the free
and voluntary act of said Harris Trust and Savings Bank for the uses and
purposes therein set forth.

      IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                        ----------------------------------------
                                          Notary Public, Cook County, Illinois

My Commission Expires on May 21, 2001.
(NOTARIAL SEAL)

                                     -9-

<PAGE>   11



Return To:                                This Instrument Was Prepared By:

      ILLINOIS POWER COMPANY              Schiff Hardin & Waite
      Real Estate Dept. F-14              7200 Sears Tower
      500 S. 27th Street                  Chicago, IL 60606
      Decatur, IL 62525






                                      -10-




<PAGE>   1
                                                                    EXHIBIT 4.43


================================================================================



                             ILLINOIS POWER COMPANY


                                       TO


                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE


                                  -------------




                             SUPPLEMENTAL INDENTURE

                            DATED AS OF JULY 15, 1998


                                       TO


                           MORTGAGE AND DEED OF TRUST

                             DATED NOVEMBER 1, 1943




================================================================================



<PAGE>   2
SUPPLEMENTAL INDENTURE dated as of July 15, 1998 (the "Supplemental Indenture"),
made by and between ILLINOIS POWER COMPANY, a corporation organized and existing
under the laws of the State of Illinois (the "Company"), party of the first
part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and existing
under the laws of the State of Illinois (the "Trustee"), as Trustee under the
Mortgage and Deed of Trust dated November 1, 1943, hereinafter mentioned, party
of the second part;

          WHEREAS, the Company has heretofore executed and delivered its
Mortgage and Deed of Trust dated November 1, 1943 ("Original Indenture"), to the
Trustee, for the security of the First Mortgage Bonds of the Company issued and
to be issued thereunder (the "Bonds"); and

          WHEREAS, pursuant to the terms and provisions of the Original
Indenture there were created and authorized by Supplemental Indentures thereto
bearing the following dates, respectively, the First Mortgage Bonds of the
series issued thereunder and respectively identified opposite such dates:



<TABLE>
<CAPTION>
      DATE OF SUPPLEMENTAL                IDENTIFICATION
            INDENTURE                       OF SERIES                             CALLED
      --------------------                --------------                          ------
<S>                                <C>                                     <C>        
November 1, 1943                   4% Series due 1973                      Bonds of the 1973 Series
                                             (redeemed)

March 1, 1946                      2 7/8% Series due 1976                  Bonds of the 1976 Series
                                             (paid at maturity)

February 1, 1948                   3 1/2% Series due 1978                  Bonds of the 1978 SeriEs
                                             (paid at maturity)

July 1, 1949                       2 7/8 % Series due 1979                 Bonds of the 1979 Series
                                             (paid at maturity)             

April 1, 1950                      2 3/4% Series due 1980                  Bonds of the 1980 SeriEs
                                             (paid at maturity)

March 1, 1952                      3 1/2% Series due 1982                  Bonds of the 1982 SeriEs
                                             (paid at maturity)

November 1, 1953                   3 1/2% Series due 1983                  Bonds of the 1983 SeriEs
                                             (paid at maturity)

July 1, 1956                       3 3/4% Series due 1986                  Bonds of the 1986 SeriEs
                                             (paid at maturity)

May 1, 1958                        4% Series due 1988                      Bonds of the 1988 Series
                                             (redeemed)

January 1, 1963                    4 1/4% Series due 1993                  Bonds of the 1993 SeriEs
                                             (paid at
                                             maturity)

October 1, 1966                    5.85% Series due 1996                   Bonds of the 1996 Series
                                             (paid at maturity)
</TABLE>



                                       -1-

<PAGE>   3


<TABLE>
<CAPTION>
      DATE OF SUPPLEMENTAL                IDENTIFICATION
            INDENTURE                       OF SERIES                             CALLED
      --------------------                --------------                          ------
<S>                                <C>                                     <C>        
January 1, 1968                    6 3/8% Series due 1998                  Bonds of the First 1998 Series
                                             (redeemed)

October 1, 1968                    6 3/4% Series due October 1,            Bonds of the Second 1998 Series
                                   1998 (redeemed)

October 1, 1969                    8.35% Series due 1999                   Bonds of the First 1999 Series
                                             (redeemed)

November 1, 1970                   9% Series due 2000                      Bonds of the 2000 Series
                                             (redeemed)

October 1, 1971                    7.60% Series due 2001                   Bonds of the 2001 Series
                                             (redeemed)

June 1, 1973                       7 5/8% Series due 2003                  Bonds of the First 2003 Series
                                             (redeemed)

May 1, 1974                        Pollution Control Series A              Bonds of the Pollution Control
                                                                           Series A

September 1, 1974                  10 1/2% Series due 2004                 Bonds of the First 2004 Series
                                             (redeemed)

July 1, 1976                       8 3/4% Series due 2006                  Bonds of the 2006 Series
                                             (redeemed)

May 1, 1977                        Pollution Control Series B              Bonds of Pollution Control
                                             (redeemed)                    Series B

November 1, 1977                   8 1/4% Series due 2007                  Bonds of the 2007 Series
                                              (redeemed)

August 1, 1978                     8 7/8% Series due 2008                  Bonds of the 2008 Series
                                             (redeemed)

July 1, 1979                       9 7/8% Series due July 1,               Bonds of the Second 2004 Series
                                   2004
                                             (redeemed)

July 31, 1980                      11 3/8% Series due 1987                 Bonds of the 1987 Series
                                             (redeemed)

August 1, 1980                     12 5/8% Series due 2010                 Bonds of the 2010 Series
                                             (redeemed)

July 1, 1982                       14 1/2% Series due 1990                 Bonds of the 1990 Series
                                             (redeemed)
</TABLE>



                                       -2-

<PAGE>   4

<TABLE>
<CAPTION>
 DATE OF SUPPLEMENTAL                     IDENTIFICATION
       INDENTURE                            OF SERIES                             CALLED
 --------------------                     --------------                          ------
<S>                                <C>                                     <C>        
November 1, 1982                   12% Series due 2012                     Bonds of the 2012 Series
                                             (redeemed)

December 15, 1983                  Pollution Control Series C              Bonds of the Pollution Control
                                             (redeemed)                    Series C

May 15, 1984                       Pollution Control Series D              Bonds of the Pollution Control
                                             (redeemed)                    Series D

March 1, 1985                      Pollution Control Series E              Bonds of the Pollution Control
                                             (redeemed)                    Series E

February 1, 1986                   10 1/2% Series due 2016                 Bonds of the First 2016 Series
                                             (redeemed)

July 1, 1986                       9 7/8% Series due 2016                  Bonds of the Second 2016 Series
                                             (redeemed)

September 1, 1986                  9 3/8% Series due 2016                  Bonds of the Third 2016 Series
                                             (redeemed)

February 1, 1987                   Pollution Control Series F              Bonds of the Pollution Control
                                             (redeemed)                    Series F

February 1, 1987                   Pollution Control Series G              Bonds of the Pollution Control
                                             (redeemed)                    Series G

February 1, 1987                   Pollution Control Series H              Bonds of the Pollution Control
                                             (redeemed)                    Series H

July 1, 1987                       Pollution Control Series I              Bonds of the Pollution Control
                                             (redeemed)                    Series I

July 1, 1988                       10% Series due 1998                     Bonds of the Third 1998 Series
                                             (redeemed)

July 1, 1991                       Pollution Control Series J              Bonds of the Pollution Control
                                                                           Series J

June 1, 1992                       Pollution Control Series K              Bonds of the Pollution Control
                                                                           Series K
June 1, 1992                       Pollution Control Series L              Bonds of the Pollution Control
                                                                           Series L
July 1, 1992                       7.95% Series due 2004                   Bonds of the Third 2004 Series

July 1, 1992                       8 3/4% Series due 2021                  Bonds of the 2021 Series

September 1, 1992                  6 1/2% Series due 1999                  Bonds of the 1999 Series

</TABLE>


                                     -3-

<PAGE>   5

<TABLE>
<CAPTION>
      DATE OF SUPPLEMENTAL                IDENTIFICATION
            INDENTURE                       OF SERIES                             CALLED
      --------------------                --------------                          ------
<S>                                <C>                                     <C>        
February 15, 1993                  8% Series due 2023                      Bonds of the 2023 Series

March 15, 1993                     6 1/8% Series due 2000                  Bonds of the 2000 Series
                                                         
March 15, 1993                     6 3/4% Series due 2005                  Bonds of the 2005 Series

July 15, 1993                      7 1/2% Series due 2025                  Bonds of the 2025 Series
                                                                           Series M

August 1, 1993                     6 1/2% Series due 2003                  Bonds of the Second 2003 Series
                                                          
October 15, 1993                   5 5/8% Series due 2000                  Bonds of the Second 2003 Series
                                                         
November 1, 1993                   Pollution Control Series M              Bonds of the Second 2003 Series
                                                             
November 1, 1993                   Pollution Control Series N              Bonds of the Pollution Control
                                                                           Series N

November 1, 1993                   Pollution Control Series O              Bonds of the Pollution Control
                                                                           Series O

April 1, 1997                      Pollution Control Series P              Bonds of the Pollution Control
                                                                           Series P

April 1, 1997                      Pollution Control Series Q              Bonds of the Pollution Control
                                                                           Series Q

April 1, 1997                      Pollution Control Series R              Bonds of the Pollution Control
                                                                           Series R

March 1, 1998                      Pollution Control Series S              Bonds of the Pollution Control
                                                                           Series S

March 1, 1998                      Pollution Control Series T              Bonds of the Pollution Control
                                                                           Series T
</TABLE>

and

          WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Original Indenture, to be known as First Mortgage Bonds, 6 1/4%
Series due 2002 (the "Bonds of the 2002 Series") and to issue additional Bonds
under the Original Indenture; and

          WHEREAS, the Bonds of the 2002 Series are to be issued to Harris Trust
and Savings Bank, as trustee (the "New Mortgage Trustee") under the Company's
General Mortgage Indenture and Deed of Trust dated as of November 1, 1992 (the
"New Mortgage") and are to be owned and held


                                       -4-

<PAGE>   6




by the New Mortgage Trustee as "Pledged Bonds" (as defined in the New Mortgage)
in accordance with the terms of the New Mortgage; and

          WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Original
Indenture, and pursuant to appropriate resolutions of the Board of Directors,
has duly resolved and determined to make, execute and deliver to the Trustee a
Supplemental Indenture in the form hereof for the purposes herein provided; and

          WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;

          NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

          THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Original Indenture and of One Dollar to it duly paid by
the Trustee at or before the ensealing and delivery of these presents, the
receipt whereof is hereby acknowledged, hereby covenants and agrees to and with
the Trustee and its successors in the trust under the Original Indenture, for
the benefit of the New Trustee and any successor holder of the Bonds as follows:

                                   ARTICLE I.

                    DESCRIPTION OF BONDS OF THE 2002 SERIES.

          SECTION 1. The Company hereby creates a new series of Bonds to be
known as "The First Mortgage Bonds, 6 1/4% Series due 2002" (the "Bonds of the
2002 Series"). The Bonds of the 2002 Series shall be executed, authenticated and
delivered in accordance with the provisions of, and shall in all respects be
subject to, all of the terms, conditions and covenants of the Original
Indenture, as supplemented and modified. The Bonds of the 2002 Series will be
issued only to the New Mortgage Trustee as security for a series of bonds being
issued under the Company's New Mortgage and the supplemental indenture to the
New Mortgage dated as of July 15, 1998 (the "New Mortgage Bonds of the 2002
Series").

          The Bonds of the 2002 Series shall be dated as provided in Section 6
of Article II of the Original Indenture and for the purposes of said Section 6
the commencement of the first interest period shall be July 21, 1998. All Bonds
of the 2002 Series shall mature on July 15, 2002, and shall bear interest at the
rate of SIX AND ONE-QUARTER per cent (6 1/4%) per annum, payable semi-annually
on July 15 and January 15 of each year, commencing January 15, 1999, until the
principal sum is paid in full. Any payment by the Company of principal of, or
interest on, any Bonds of the 2002 Series shall be applied by the New Mortgage
Trustee to the payment of any principal or interest, as the case may be, in
respect of the New Mortgage Bonds of the 2002 Series due in accordance with the
terms of the New Mortgage.

          SECTION 2. The Bonds of the 2002 Series and the Trustee's Certificate
shall be substantially in the following forms respectively:






                                       -5-

<PAGE>   7





                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                   FIRST MORTGAGE BOND, 6 1/4% SERIES DUE 2002

No. .............                                                   $100,000,000

          ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to Harris Trust and Savings Bank as
trustee (the "New Mortgage Trustee") under the Company's General Mortgage
Indenture and Deed of Trust dated as of November 1, 1992 (the "New Mortgage") or
its registered assigns, the principal sum of One Hundred Million Dollars
($100,000,000) on July 15, 2002, in any coin or currency of the United States of
America which at the time of payment is legal tender for public and private
debts, and to pay interest thereon in like coin or currency from July 21, 1998,
payable semi-annually on July 15 and January 15 in each year, commencing January
15, 1999, at the rate of SIX AND ONE-QUARTER percent (6 1/4%) per annum, until
the Company's obligation with respect to the payment of such principal shall be
discharged as provided in the Indenture. Both the principal of, and the interest
on, this Bond are payable at the agency of the Company in the City of Chicago,
Illinois.

          This First Mortgage Bond shall not be entitled to any benefit under
the Indenture or any indenture supplemental thereto, or become valid or
obligatory for any purpose, until the form of certificate endorsed hereon shall
have been signed by or on behalf of Harris Trust and Savings Bank, the Trustee
under the Indenture, or a successor trustee thereto under the Indenture (the
"Trustee").

          The provisions of this First Mortgage Bond are continued on the
reverse hereof and such continued provisions shall for all purposes have the
same effect as though fully set forth at this place.

          IN WITNESS WHEREOF, Illinois Power Company has caused this First
Mortgage Bond to be signed (manually or by facsimile signature) in its name by
its President or a Vice President, and its corporate seal (or a facsimile
thereof) to be hereto affixed and attested (manually or by facsimile signature)
by its Secretary or an Assistant Secretary.


Dated . . . . . . . . . . . . .                       ILLINOIS POWER COMPANY,


                                                      By  . . . . . . . . . . . 
                                                           Vice President

ATTEST:


 . . . . . . . . . .  . . . . . . . . . .
          Assistant Secretary


                                       -6-

<PAGE>   8





                         [FORM OF TRUSTEE'S CERTIFICATE]

          This First Mortgage Bond is one of the Bonds of the series designated
therein, described in the within-mentioned Indenture and the Supplemental
Indenture dated as of July 15, 1998.


                                                  HARRIS TRUST AND SAVINGS BANK,
                                                                        Trustee,

                                                  By . . . . . . . . . . . . . .
                                                           Authorized Officer

                            [FORM OF REVERSE OF BOND)

          This First Mortgage Bond is one of a duly authorized issue of Bonds of
the Company (the "Bonds") in unlimited aggregate principal amount, of the series
hereinafter specified, all issued and to be issued under and equally secured by
the Mortgage and Deed of Trust (the "Indenture"), dated November 1, 1943,
executed by the Company to Harris Trust and Savings Bank (the "Trustee"), as
Trustee, to which Indenture and all indentures supplemental thereto, including
the Supplemental Indenture dated February 15, 1993, which amended Section 1 of
Article IX of the Indenture, reference is hereby made for a description of the
properties mortgaged and pledged, the nature and extent of the security, the
rights of the registered owners of the Bonds and of the Trustee in respect
thereof, and the terms and conditions upon which the Bonds are, and are to be,
secured. The Bonds may be issued in series, for various principal sums, may
mature at different times, may bear interest at different rates and may
otherwise vary as in the Indenture provided. This First Mortgage Bond is one of
a series designated as the First Mortgage Bonds, 6 1/4% Series Due 2002 (the
"Bonds of the 2002 Series") of the Company, unlimited in aggregate principal
amount, issued under and secured by the Indenture and described in the
supplemental indenture dated as of July 15, 1998 (the "Supplemental Indenture of
July 15, 1998"), between the Company and the Trustee, supplemental to the
Indenture.

          To the extent permitted by, and as provided in, the Indenture,
modifications or alterations of the Indenture, or of any indenture supplemental
thereto, and of the rights and obligations of the Company and of the holders of
the Bonds and coupons may be made with the consent of the Company by an
affirmative vote of the holders of not less than 662/3% in amount of the Bonds
entitled to vote then outstanding, at a meeting of Bondholders called and held
as provided in the Indenture, and by an affirmative vote of the holders of not
less than 662/3% in amount of the Bonds of any series entitled to vote then
outstanding and affected by such modification or alteration, in case one or more
but less than all of the series of Bonds then outstanding under the Indenture
are so affected; provided however, that no such modification or alteration shall
be made which will affect the terms of payment of the principal of, or interest
or premium, if any, on this First Mortgage Bond.



                                       -7-

<PAGE>   9




          In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the Bonds at any such time outstanding under the Indenture
may be declared or may become due and payable, upon the conditions and in the
manner and with the effect provided in the Indenture. The Indenture provides
that such declaration may in certain events be rescinded by the holders of a
majority in principal amount of the Bonds outstanding.

          No recourse shall be had for the payment of the principal of, or
premium or interest on this First Mortgage Bond, or for any claim based hereon
or on the Indenture or any indenture supplemental thereto, against any
incorporator, or against any stockholder, director or officer, as such, past,
present or future, of the Company, or of any predecessor or successor
corporation, either directly or through the Company or any such predecessor or
successor corporation, whether by virtue of any constitution, statute or rule of
law, or by the enforcement of any assessment or penalty or otherwise, all such
liability, whether at common law, in equity, by any constitution, statute, rule
of law, or otherwise, of incorporators, stockholders, directors or officers
being released by every owner hereof by the acceptance of this First Mortgage
Bond and as part of the consideration for the issue hereof, and being likewise
released by the terms of the Indenture; provided, however, that nothing herein
or in the Indenture or any indenture supplemental thereto contained shall
prevent the enforcement of the liability, if any, of any stockholder or
subscriber to capital stock upon or in respect of shares of capital stock not
fully paid up.

          Notwithstanding any provision in the Indenture, the Supplemental
Indenture of July 15, 1998 or this First Mortgage Bond to the contrary, any
payment by the Company under the New Mortgage of principal of, or interest on,
bonds which shall have been authenticated and delivered under the New Mortgage
(the "New Mortgage Bonds of the 2002 Series") upon the basis of the issuance and
delivery to the New Mortgage Trustee of the Bonds of the 2002 Series shall, to
the extent thereof, be deemed to satisfy and discharge the obligation of the
Company to make a payment of principal or interest, as the case may be, in
respect of this First Mortgage Bond which is then due.

          This First Mortgage Bond constitutes a "Pledged Bond" (as defined in
the New Mortgage) and is subject to all of the rights and restrictions
applicable to Pledged Bonds as set forth in the New Mortgage. Without limiting
the generality of the foregoing, this First Mortgage Bond shall be subject to
surrender by the New Mortgage Trustee in accordance with the provisions of
Section 7.03 of the New Mortgage. To the extent that any provisions in the
Indenture, the Supplemental Indenture of July 15, 1998 or this First Mortgage
Bond are inconsistent with the provisions relating to Pledged Bonds that are set
forth in the New Mortgage, the provisions of the New Mortgage shall apply.

          SECTION 3. Notwithstanding any provision in the Original Indenture,
this Supplemental Indenture, or the Bonds of the 2002 Series to the contrary,
any payment by the Company under the New Mortgage of principal of, or interest
on, bonds which shall have been authenticated and delivered under the New
Mortgage (the "New Mortgage Bonds of the 2002 Series") upon the basis of the
issuance and delivery to the New Mortgage Trustee of the Bonds of the 2002
Series shall, to the extent thereof, be deemed to satisfy and discharge the
obligation of the Company to make any


                                       -8-

<PAGE>   10




payment of principal or interest, as the case may be, in respect of the Bonds of
the 2002 Series which is then due.

          SECTION 4. The Bonds of the 2002 Series constitute "Pledged Bonds" (as
defined in the New Mortgage) and are subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, the Bonds of the 2002 Series
shall be subject to surrender by the New Mortgage Trustee in accordance with the
provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Original Indenture, this Supplemental Indenture or the Bonds
of the 2002 Series are inconsistent with the provisions relating to Pledged
Bonds that are set forth in the New Mortgage, the provisions of the New Mortgage
shall apply.


                                   ARTICLE II.

                       ISSUE OF BONDS OF THE 2002 SERIES.

          SECTION 1. The Company hereby exercises the right to obtain the
authentication of $100,000,000 principal amount of additional Bonds pursuant to
the terms of Section 4 of Article III of the Original Indenture on the basis of
75% of the net bondable value of property additions not subject to an unfunded
prior lien. All such additional Bonds shall be Bonds of the 2002 Series.

          SECTION 2. Such Bonds of the 2002 Series may be authenticated and
delivered prior to the filing for recordation of this Supplemental Indenture.

          SECTION 3. Notwithstanding any provision in the Original Indenture to
the contrary, execution of the Bonds of the 2002 Series on behalf of the
Company, and the attesting of the corporate seal of the Company affixed to the
Bonds of the 2002 Series by the officers of the Company authorized to do such
acts by Section 12 of Article II of the Original Indenture may be validly done
either by the manual or the facsimile signatures of such authorized officers of
the Company.


                                  ARTICLE III.

                                   REDEMPTION.

        The Bonds of the 2002 Series shall not be redeemable prior to maturity.




                                       -9-

<PAGE>   11




                                   ARTICLE IV.

                                  THE TRUSTEE.

        The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Original
Indenture set forth and upon the following terms and conditions:

               The Trustee shall not be responsible in any manner whatsoever for
        or in respect of the validity or sufficiency of this Supplemental
        Indenture or the due execution hereof by the Company or for or in
        respect of the recitals contained herein, all of which recitals are made
        by the Company solely. In general, each and every term and condition
        contained in Article XIII of the Original Indenture shall apply to this
        Supplemental Indenture with the same force and effect as if the same
        were herein set forth in full, with such omissions, variations and
        modifications thereof as may be appropriate to make the same conform to
        this Supplemental Indenture.


                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

        This Supplemental Indenture may be simultaneously executed in any number
of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.




                                      -10-

<PAGE>   12




        IN WITNESS WHEREOF, Illinois Power Company has caused this Supplemental
Indenture to be executed on its behalf by its Chairman and President, one of its
Executive Vice Presidents, one of its Senior Vice Presidents or one of its Vice
Presidents and its corporate seal to be hereto affixed and said seal and this
Supplemental Indenture to be attested by its Secretary or one of its Assistant
Secretaries; and said Harris Trust and Savings Bank, in evidence of its
acceptance of the trust hereby created, has caused this Supplemental Indenture
to be executed on its behalf by its President or one of its Vice Presidents and
its corporate seal to be hereto affixed and said seal and this Supplemental
Indenture to be attested by its Secretary or one of its Assistant Secretaries;
all as of the fifteenth day of July, 1998.

                                             ILLINOIS POWER COMPANY


                                             By   /s/ ROBERT A. SCHULTZ
                                               ---------------------------------
                                                   Robert A. Schultz
                                                   Vice President - Finance


(CORPORATE SEAL)


ATTEST:


  /s/ ELIZABETH A. O'DONNELL          
- --------------------------------------
Elizabeth A. O'Donnell
Assistant Secretary


                                          HARRIS TRUST AND SAVINGS BANK, Trustee


                                          By  /s/ J. BARTOLINI                  
                                            ------------------------------------
                                                 J. Bartolini
                                                 Vice President

(CORPORATE SEAL)

ATTEST:


  /s/ C. POTTER        
- -------------------------------------
C. Potter
Assistant Secretary


                                      -11-

<PAGE>   13




STATE OF ILLINOIS             )
                              ) SS.:
COUNTY OF MACON               )

        BE IT REMEMBERED, that on this 11th day of June, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President - Finance and Elizabeth A.
O'Donnell, Assistant Secretary, of Illinois Power Company, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be such officers, and who are personally known
to me to be the same persons who executed as such officers the within instrument
of writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such officers
and as the free and voluntary act of said Illinois Power Company for the uses
and purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                           -------------------------------------
                                           Notary Public, Macon County, Illinois



My Commission Expires on _________________.

(NOTARIAL SEAL)


STATE OF ILLINOIS             )
                              ) SS.:
COUNTY OF COOK                )

        BE IT REMEMBERED, that on this 12th day of June, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President, and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such Vice President and Secretary, respectively, and as the
free and voluntary act of said Harris Trust and Savings Bank for the uses and
purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.


                                            ------------------------------------
                                            Notary Public, Cook County, Illinois




My Commission Expires on May 21, 2001.
(NOTARIAL SEAL)


                                      -12-

<PAGE>   14







        Return To:                             This Instrument Was Prepared By:

        ILLINOIS POWER COMPANY                 SCHIFF HARDIN & WAITE
        Real Estate Dept. F-14                 6600 Sears Tower
        500 S. 27th Street                     233 South Wacker Drive
        Decatur, IL 62525                      Chicago, IL  60606





                                      -13-

<PAGE>   1
                                                                    EXHIBIT 4.44


================================================================================





                             ILLINOIS POWER COMPANY

                                       TO

                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE

                               ------------------


                             SUPPLEMENTAL INDENTURE

                            DATED AS OF JULY 15, 1998

                                       TO

                  GENERAL MORTGAGE INDENTURE AND DEED OF TRUST

                          DATED AS OF NOVEMBER 1, 1992



================================================================================








<PAGE>   2




SUPPLEMENTAL INDENTURE dated as of July 15, 1998 (the "Supplemental Indenture"),
made by and between ILLINOIS POWER COMPANY, a corporation organized and existing
under the laws of the State of Illinois (the "Company"), party of the first
part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and existing
under the laws of the State of Illinois (the "Trustee"), as Trustee under the
General Mortgage indenture and Deed of Trust dated as of November 1, 1992,
hereinafter mentioned, party of the second part;

        WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 (the
"Indenture"), to the Trustee, for the security of the Bonds of the Company
issued and to be issued thereunder (the "Bonds"); and

        WHEREAS, pursuant to the terms and provisions of the Indenture there
were created and authorized by Supplemental Indentures thereto bearing the
following dates, respectively, the New Mortgage Bonds of the series issued
thereunder and respectively identified opposite such dates:


<TABLE>
<CAPTION>
    DATE OF SUPPLEMENTAL            Identification
          INDENTURE                    of Series                             Called
         -----------                  -----------                            ------
<S>                          <C>                              <C>        
February 15, 1993             8% Series due 2023              Bonds of the 2023 Series
March 15, 1993               6 1/2% Series due 2000           Bonds of the 2000 Series
March 15, 1993               6 3/4% Series due 2005           Bonds of the 2005 Series
July 15, 1993                7 1/2% Series due 2025           Bonds of the 2025 Series
August 1, 1993               6 1/2% Series due 2003           Bonds of the 2003 Series
October 15, 1993             5 5/8% Series due 2000        Bonds of the Second 2000 Series
November 1, 1993             Pollution Control Series M    Bonds of the Pollution Control Series M
November 1, 1993             Pollution Control Series N    Bonds of the Pollution Control Series N
November 1, 1993             Pollution Control Series O    Bonds of the Pollution Control Series O
April 1, 1997                Pollution Control Series P    Bonds of the Pollution Control Series P
April 1, 1997                Pollution Control Series Q    Bonds of the Pollution Control Series Q
April 1, 1997                Pollution Control Series R    Bonds of the Pollution Control Series R
March 1, 1998                Pollution Control Series S    Bonds of the Pollution Control Series S
March 1, 1998                Pollution Control Series T    Bonds of the Pollution Control Series T
</TABLE>


        WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Indenture, to be known as New Mortgage Bonds, 6 1/4% Series due
2002 (the "New Mortgage Bonds of the 2002 Series"); and

        WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the indenture, and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and determined to make, execute and deliver to the Trustee a Supplemental
Indenture in the form hereof for the purposes herein provided; and

        WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;

        NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

        THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of One Dollar to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, hereby covenants and agrees to and with the Trustee



                                      2

<PAGE>   3




and its successors in the trust under the Indenture, for the benefit of those
who shall hold the Bonds as follows:


                                   ARTICLE I.

              DESCRIPTION OF NEW MORTGAGE BONDS OF THE 2002 SERIES.

        SECTION 1. The Company hereby creates a new series of Bonds to be known
as the "New Mortgage Bonds of the 2002 Series." The New Mortgage Bonds of the
2002 Series shall be executed, authenticated and delivered in accordance with
the provisions of, and shall in all respects be subject to, all of the terms,
conditions and covenants of the Indenture, as supplemented and modified.

        The commencement of the first interest period shall be July 21, 1998.
All New Mortgage Bonds of the 2002 Series shall mature on July 15, 2002, and
shall bear interest at the rate of SIX AND ONE-QUARTER PER CENT (6 1/4%) per
annum, payable semi-annually on July 15 and January 15 in each year. The person
in whose name any of the New Mortgage Bonds of the 2002 Series are registered at
the close of business on any record date (as hereinafter defined) with respect
to any interest payment date shall be entitled to receive the interest payable
on such interest payment date notwithstanding the cancellation of such New
Mortgage Bonds of the 2002 Series upon any transfer or exchange subsequent to
the record date and prior to such interest payment date; provided, however, that
if and to the extent the Company shall default in the payment of the interest
due on such interest payment date, such defaulted interest shall be paid as
provided in Section 3.07 of the Indenture.

        The term "record date" as used in this Section with respect to any
interest payment date shall mean the July 1 or January 1, as the case may be,
next preceding the semi-annual interest payment date, or, if such July 1 or
January 1 shall be a legal holiday or a day on which banking institutions in the
City of Chicago, Illinois, are authorized by law to close, then the next
preceding day which shall not be a legal holiday or a day on which such
institutions are so authorized to close.

        SECTION 2. The New Mortgage Bonds of the 2002 Series shall be issued
only as registered Bonds without coupons of the denomination of $1,000, or any
integral multiple of $1,000, appropriately numbered. The New Mortgage Bonds of
the 2002 Series may be exchanged, upon surrender thereof, at the agency of the
Company in the City of Chicago, Illinois, for one or more New Mortgage Bonds of
the 2002 Series of other authorized denominations, for the same aggregate
principal amount, subject to the terms and conditions set forth in the
Indenture.

        New Mortgage Bonds of the 2002 Series may be exchanged or transferred
without expense to the registered owner thereof except that any taxes or other
governmental charges required to be paid with respect to such transfer or
exchange shall be paid by the registered owner requesting such transfer or
exchange as a condition precedent to the exercise of such privilege.

        SECTION 3. The New Mortgage Bonds of the 2002 Series and the Trustee's
Certificate of Authentication shall be substantially in the following forms
respectively:



                                        3

<PAGE>   4




                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                    NEW MORTGAGE BOND, 6 1/4% SERIES DUE 2002

No. . . . . . . . . . . . . .                                       $100,000,000

        ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to ........ or registered assigns, the
principal sum of One Hundred Million Dollars ($100,000,000) on July 15, 2002, in
any coin or currency of the United States of America which at the time of
payment is legal tender for public and private debts, and to pay interest
thereon in like coin or currency from July 21, 1998, payable semi-annually on1
July 15 and January 15 in each year, commencing January 15, 1999, at the rate of
SIX AND ONE-QUARTER per cent (6 1/4%) per annum, until the Company's obligation
with respect to the payment of such principal shall be discharged as provided in
the Indenture hereinafter mentioned. The interest so payable on any July 15 or
January 15 will, subject to certain exceptions provided in the Supplemental
Indenture dated as of July 15, 1998, be paid to the person in whose name this
New Mortgage Bond is registered at the close of business on the immediately
preceding July 1 or January 1, as the case may be. Both principal of, and
interest on, this New Mortgage Bond are payable at the agency of the Company in
the City of Chicago, Illinois.

        This New Mortgage Bond shall not be entitled to any benefit under the
Indenture or any indenture supplemental thereto, or become valid or obligatory
for any purpose, until the form of certificate endorsed hereon shall have been
signed by or on behalf of Harris Trust and Savings Bank, the Trustee under the
Indenture, or a successor trustee thereto under the Indenture (the "Trustee").

        The provisions of this New Mortgage Bond are continued on the reverse
hereof and such continued provisions shall for all purposes have the same effect
as though fully set forth at this place.

        IN WITNESS WHEREOF, Illinois Power Company has caused this New Mortgage
Bond to be signed (manually or by facsimile signature) in its name by an
Authorized Executive Officer, as defined in the Indenture, and its corporate
seal (or a facsimile thereof) to be hereto affixed and attested (manually or by
facsimile signature) by an Authorized Executive Officer, as defined in the
Indenture.

Dated  . . . . . . . . . . . .               ILLINOIS POWER COMPANY,


                                             By ................................
                                                 Authorized Executive Officer

ATTEST:

 ........................................
    Authorized Executive Officer



                                        4


<PAGE>   5




                        [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

        This New Mortgage Bond is one of the Bonds of the series designated
therein referred to in the within-mentioned Indenture dated as of November 1,
1992 and the Supplemental Indenture dated as of July 15, 1998.


                                             HARRIS TRUST AND SAVINGS BANK,
                                                                        Trustee,


                                             By ................................
                                                      Authorized Signatory


                            [FORM OF REVERSE OF BOND]

        This New Mortgage Bond is one of a duly authorized issue of Bonds of the
Company (the "Bonds") in unlimited aggregate principal amount, of the series
hereinafter specified, all issued and to be issued under and equally secured by
a General Mortgage Indenture and Deed of Trust (the "Indenture"), dated as of
November 1, 1992, executed by the Company to Harris Trust and Savings Bank (the
"Trustee"), as Trustee, to which Indenture and all indentures supplemental
thereto reference is hereby made for a description of the properties mortgaged
and pledged, the nature and extent of the security, the rights of registered
owners of the Bonds and of the Trustee in respect thereof, and the terms and
conditions upon which the Bonds are, and are to be, secured. The Bonds may be
issued in series, for various principal sums, may mature at different times, may
bear interest at different rates and may otherwise vary as provided in the
Indenture. This New Mortgage Bond of the 2002 Series is one of a series
designated as the "New Mortgage Bonds, 6 1/4% Series Due 2002" (the "New
Mortgage Bonds of the 2002 Series") of the Company, unlimited in aggregate
principal amount, issued under and secured by the Indenture and described in the
supplemental indenture dated as of July 15, 1998 (the "Supplemental Indenture
dated as of July 15, 1998"), between the Company and the Trustee, supplemental
to the Indenture.

        The New Mortgage Bonds of the 2002 Series are not subject to redemption
prior to maturity.

        In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the Bonds at any such time outstanding under the Indenture
may be declared or may become due and payable, upon the conditions and in the
manner and with the effect provided in the Indenture. The Indenture provides
that such declaration may be rescinded under certain circumstances.


                                   ARTICLE II.

                 ISSUE OF NEW MORTGAGE BONDS OF THE 2002 SERIES.

         SECTION 1. The Company hereby exercises the right to obtain the
authentication of $100,000,000 principal amount of Bonds pursuant to the terms
of Section 4.02 of the Indenture. All such Bonds shall be New Mortgage Bonds of
the 2002 Series.

        SECTION 2. Such New Mortgage Bonds of the 2002 Series may be
authenticated and delivered prior to the filing for recordation of this
Supplemental Indenture.



                                        5

<PAGE>   6




                                  ARTICLE III.

                                   REDEMPTION.

        The New Mortgage Bonds of the 2002 Series shall not be redeemable prior
to maturity.

                                   ARTICLE IV.

                                  THE TRUSTEE.

        The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:

               The Trustee shall not be responsible in any manner whatsoever for
        or in respect of the validity or sufficiency of this Supplemental
        Indenture or the due execution hereof by the Company or for or in
        respect of the recitals contained herein, all of which recitals are made
        by the Company solely. In general, each and every term and condition
        contained in Article Eleven of the Indenture shall apply to this
        Supplemental Indenture with the same force and effect as if the same
        were herein set forth in full, with such omissions, variations and
        modifications thereof as may be appropriate to make the same conform to
        this Supplemental Indenture.

                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

        This Supplemental Indenture may be simultaneously executed in any number
of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.



                                        6

<PAGE>   7




        IN WITNESS WHEREOF, Illinois Power Company has caused this Indenture to
be executed on its behalf by an Authorized Executive Officer as defined in the
Indenture, and its corporate seal to be hereto affixed and said seal and this
Indenture to be attested by an Authorized Executive Officer as defined in the
Indenture; and said Harris Trust and Savings Bank, in evidence of its acceptance
of the trust hereby created, has caused this Indenture to be executed on its
behalf by its President or one of its Vice Presidents and its corporate seal to
be hereto affixed and said seal and this Indenture to be attested by its
Secretary or one of its Assistant Secretaries; all as of the fifteenth day of
July, 1998.

                                             ILLINOIS POWER COMPANY


                                             By   /s/ ROBERT A. SCHULTZ         
                                                --------------------------------
(CORPORATE SEAL)                                      Robert A. Schultz
                                                      Vice President - Finance


ATTEST:

/s/ ELIZABETH A. O'DONNELL   
- -------------------------------
Elizabeth A. O'Donnell
Assistant Secretary



                                             HARRIS TRUST AND SAVINGS BANK,
                                                                         Trustee

                                             By   /s/ J. BARTOLINI 
                                                --------------------------------
(CORPORATE SEAL)                                      J. Bartolini
                                                      Vice President


ATTEST:

/s/ C. POTTER          
- ------------------------
C. Potter
Assistant Secretary



                                        7

<PAGE>   8




STATE OF ILLINOIS             )
                              )  SS.:
COUNTY OF MACON               )

        BE IT REMEMBERED, that on this 11th day of June, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President - Finance and Elizabeth A.
O'Donnell, Assistant Secretary, of Illinois Power Company, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be such officers, and who are personally known
to me to be the same persons who executed as such officers the within instrument
of writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such officers,
and as the free and voluntary act of said Illinois Power Company for the uses
and purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                           -------------------------------------
                                           Notary Public, Macon County, Illinois

My Commission Expires _______________.

(NOTARIAL SEAL)



STATE OF ILLINOIS             )
                              ) SS.:
COUNTY OF COOK                )

        BE IT REMEMBERED, that on this 12th day of June, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such officers, and as the free and voluntary act of said Harris
Trust and Savings Bank for the uses and purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.


                                            ------------------------------------
                                            Notary Public, Cook County, Illinois

My Commission Expires: May 21, 2001

(NOTARIAL SEAL)

                                      8

<PAGE>   9





Return To:                                    This Instrument Was Prepared By:

        ILLINOIS POWER COMPANY                       SCHIFF HARDIN & WAITE
        Real Estate Dept. F-14                       6600 Sears Tower
        500 S. 27th Street                           233 South Wacker Drive
        Decatur, IL 62525                            Chicago, IL 60606






                                       9

<PAGE>   1
                                                                    EXHIBIT 4.45


================================================================================




                             ILLINOIS POWER COMPANY


                                       TO


                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE


                                  -------------




                             SUPPLEMENTAL INDENTURE

                         DATED AS OF SEPTEMBER 15, 1998


                                       TO


                           MORTGAGE AND DEED OF TRUST

                             DATED NOVEMBER 1, 1943




================================================================================



<PAGE>   2




SUPPLEMENTAL INDENTURE dated as of September 15, 1998 (the "Supplemental
Indenture"), made by and between ILLINOIS POWER COMPANY, a corporation organized
and existing under the laws of the State of Illinois (the "Company"), party of
the first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the Mortgage and Deed of Trust dated November 1, 1943, hereinafter
mentioned, party of the second part;

          WHEREAS, the Company has heretofore executed and delivered its
Mortgage and Deed of Trust dated November 1, 1943 ("Original Indenture"), to the
Trustee, for the security of the First Mortgage Bonds of the Company issued and
to be issued thereunder (the "Bonds"); and

          WHEREAS, pursuant to the terms and provisions of the Original
Indenture there were created and authorized by Supplemental Indentures thereto
bearing the following dates, respectively, the First Mortgage Bonds of the
series issued thereunder and respectively identified opposite such dates:



<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL                     IDENTIFICATION
    INDENTURE                              OF SERIES                               CALLED
- --------------------                     --------------                            ------
<S>                                <C>                                     <C>        
November 1, 1943                   4% Series due 1973                      Bonds of the 1973 Series
                                             (redeemed)

March 1, 1946                      2 7/8% Series due 1976                  Bonds of the 1976 Series
                                             (paid at maturity)

February 1, 1948                   3 1/2% Series due 1978                  Bonds of the 1978 SeriEs
                                             (paid at maturity)

July 1, 1949                       2 7/8 % Series due 1979                 Bonds of the 1979 Series
                                             (paid at maturity)             
 
April 1, 1950                      2 3/4% Series due 1980                  Bonds of the 1980 SeriEs
                                             (paid at maturity)

March 1, 1952                      3 1/2% Series due 1982                  Bonds of the 1982 SeriEs
                                             (paid at maturity)

November 1, 1953                   3 1/2% Series due 1983                  Bonds of the 1983 SeriEs
                                              (paid at maturity)

July 1, 1956                       3 3/4% Series due 1986                  Bonds of the 1986 SeriEs
                                             (paid at maturity)

May 1, 1958                        4% Series due 1988                      Bonds of the 1988 Series
                                             (redeemed)

January 1, 1963                    4 1/4% Series due 1993                  Bonds of the 1993 SeriEs
                                             (paid at
                                             maturity)

October 1, 1966                    5.85% Series due 1996                   Bonds of the 1996 Series
                                             (paid at maturity)

</TABLE>


                                       -2-

<PAGE>   3

<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL                     IDENTIFICATION
    INDENTURE                              OF SERIES                               CALLED
- --------------------                     --------------                            ------
<S>                                <C>                                     <C>        
January 1, 1968                    6 3/8% Series due 1998                   Bonds of the First 1998 Series
                                             (redeemed)

October 1, 1968                    6 3/4% Series due October 1,             Bonds of the Second 1998 Series
                                   1998 (redeemed)

October 1, 1969                    8.35% Series due 1999                    Bonds of the First 1999 Series
                                             (redeemed)

November 1, 1970                   9% Series due 2000                       Bonds of the 2000 Series
                                             (redeemed)

October 1, 1971                    7.60% Series due 2001                    Bonds of the 2001 Series
                                             (redeemed)

June 1, 1973                       7 5/8% Series due 2003                   Bonds of the First 2003 Series
                                             (redeemed)

May 1, 1974                        Pollution Control Series A               Bonds of the Pollution Control
                                                                            Series A
September 1, 1974                  10 1/2% Series due 2004                  Bonds of the First 2004 Series
                                             (redeemed)

July 1, 1976                       8 3/4% Series due 2006                   Bonds of the 2006 Series
                                             (redeemed)

May 1, 1977                        Pollution Control Series B               Bonds of Pollution Control
                                             (redeemed)                     Series B

November 1, 1977                   8 1/4% Series due 2007                   Bonds of the 2007 Series
                                              (redeemed)

August 1, 1978                     8 7/8% Series due 2008                   Bonds of the 2008 Series
                                             (redeemed)

July 1, 1979                       9 7/8% Series due July 1,                Bonds of the Second 2004 Series
                                   2004
                                             (redeemed)

July 31, 1980                      11 3/8% Series due 1987                  Bonds of the 1987 Series
                                             (redeemed)

August 1, 1980                     12 5/8% Series due 2010                  Bonds of the 2010 Series
                                             (redeemed)

July 1, 1982                       14 1/2% Series due 1990                  Bonds of the 1990 Series
                                             (redeemed)

</TABLE>


                                       -3-

<PAGE>   4
<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL                     IDENTIFICATION
    INDENTURE                              OF SERIES                               CALLED
- --------------------                     --------------                            ------
<S>                                <C>                                     <C>        
November 1, 1982                   12% Series due 2012                     Bonds of the 2012 Series
                                             (redeemed)

December 15, 1983                  Pollution Control Series C              Bonds of the Pollution Control
                                             (redeemed)                    Series C

May 15, 1984                       Pollution Control Series D              Bonds of the Pollution Control
                                             (redeemed)                    Series D

March 1, 1985                      Pollution Control Series E              Bonds of the Pollution Control
                                             (redeemed)                    Series E

February 1, 1986                   10 1/2% Series due 2016                 Bonds of the First 2016 Series
                                             (redeemed)

July 1, 1986                       9 7/8% Series due 2016                  Bonds of the Second 2016 Series
                                             (redeemed)

September 1, 1986                  9 3/8% Series due 2016                  Bonds of the Third 2016 Series
                                             (redeemed)

February 1, 1987                   Pollution Control Series F              Bonds of the Pollution Control
                                             (redeemed)                    Series F

February 1, 1987                   Pollution Control Series G              Bonds of the Pollution Control
                                             (redeemed)                    Series G

February 1, 1987                   Pollution Control Series H              Bonds of the Pollution Control
                                             (redeemed)                    Series H

July 1, 1987                       Pollution Control Series I              Bonds of the Pollution Control
                                             (redeemed)                    Series I

July 1, 1988                       10% Series due 1998                     Bonds of the Third 1998 Series
                                             (redeemed)

July 1, 1991                       Pollution Control Series J              Bonds of the Pollution Control
                                                                           Series J

June 1, 1992                       Pollution Control Series K              Bonds of the Pollution Control
                                                                           Series K

June 1, 1992                       Pollution Control Series L              Bonds of the Pollution Control
                                                                           Series L

July 1, 1992                       7.95% Series due 2004                   Bonds of the Third 2004 Series

July 1, 1992                       8 3/4% Series due 2021                  Bonds of the 2021 Series

September 1, 1992                  6 1/2% Series due 1999                  Bonds of the 1999 Series

</TABLE>


                                       -4-

<PAGE>   5

<TABLE>
<CAPTION>
DATE OF SUPPLEMENTAL                     IDENTIFICATION
    INDENTURE                              OF SERIES                               CALLED
- --------------------                     --------------                            ------
<S>                                <C>                                     <C>        
February 15, 1993                  8% Series due 2023                      Bonds of the 2023 Series

March 15, 1993                     6 1/8% Series due 2000                  Bonds of the 2000 Series

March 15, 1993                     6 3/4% Series due 2005                  Bonds of the 2005 Series

July 15, 1993                      7 1/2% Series due 2025                  Bonds of the 2025 Series

August 1, 1993                     6 1/2% Series due 2003                  Bonds of the Second 2003 Series 

October 15, 1993                   5 5/8% Series due 2000                  Bonds of the Second 2000 Series 

November 1, 1993                   Pollution Control Series M              Bonds of the Pollution Control
                                                                           Series M

November 1, 1993                   Pollution Control Series N              Bonds of the Pollution Control
                                                                           Series N

November 1, 1993                   Pollution Control Series O              Bonds of the Pollution Control
                                                                           Series O

April 1, 1997                      Pollution Control Series P              Bonds of the Pollution Control
                                                                           Series P

April 1, 1997                      Pollution Control Series Q              Bonds of the Pollution Control
                                                                           Series Q

April 1, 1997                      Pollution Control Series R              Bonds of the Pollution Control
                                                                           Series R

March 1, 1998                      Pollution Control Series S              Bonds of the Pollution Control
                                                                           Series S

March 1, 1998                      Pollution Control Series T              Bonds of the Pollution Control
                                                                           Series T

July 15, 1998                      6 1/4% Series due 2002                  Bonds of the 2002 Series

</TABLE>


and

          WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Original Indenture, to be known as First Mortgage Bonds, 6%
Series due 2003 (the "Bonds of the Third 2003 Series") and to issue additional
Bonds under the Original Indenture; and



                                       -5-

<PAGE>   6




          WHEREAS, the Bonds of the Third 2003 Series are to be issued to Harris
Trust and Savings Bank, as trustee (the "New Mortgage Trustee") under the
Company's General Mortgage Indenture and Deed of Trust dated as of November 1,
1992 (the "New Mortgage") and are to be owned and held by the New Mortgage
Trustee as "Pledged Bonds" (as defined in the New Mortgage) in accordance with
the terms of the New Mortgage; and

          WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Original
Indenture, and pursuant to appropriate resolutions of the Board of Directors,
has duly resolved and determined to make, execute and deliver to the Trustee a
Supplemental Indenture in the form hereof for the purposes herein provided; and

          WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;

          NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

          THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Original Indenture and of One Dollar to it duly paid by
the Trustee at or before the ensealing and delivery of these presents, the
receipt whereof is hereby acknowledged, hereby covenants and agrees to and with
the Trustee and its successors in the trust under the Original Indenture, for
the benefit of the New Trustee and any successor holder of the Bonds as follows:

                                   ARTICLE I.

                 DESCRIPTION OF BONDS OF THE THIRD 2003 SERIES.

          SECTION 1. The Company hereby creates a new series of Bonds to be
known as "The First Mortgage Bonds, 6% Series due 2003" (the "Bonds of the Third
2003 Series"). The Bonds of the Third 2003 Series shall be executed,
authenticated and delivered in accordance with the provisions of, and shall in
all respects be subject to, all of the terms, conditions and covenants of the
Original Indenture, as supplemented and modified. The Bonds of the Third 2003
Series will be issued only to the New Mortgage Trustee as security for a series
of bonds being issued under the Company's New Mortgage and the supplemental
indenture to the New Mortgage dated as of September 15, 1998 (the "New Mortgage
Bonds of the Second 2003 Series").

          The Bonds of the Third 2003 Series shall be dated as provided in
Section 6 of Article II of the Original Indenture and for the purposes of said
Section 6 the commencement of the first interest period shall be September 16,
1998. All Bonds of the Third 2003 Series shall mature on September 15, 2003, and
shall bear interest at the rate of SIX PER CENT (6%) per annum, payable
semi-annually on March 15 and September 15 of each year, commencing March 15,
1999, until the principal sum is paid in full. Any payment by the Company of
principal of, or interest on, any Bonds of the Third 2003 Series shall be
applied by the New Mortgage Trustee to the payment of any principal or interest,
as the case may be, in respect of the New Mortgage Bonds of the Second 2003
Series due in accordance with the terms of the New Mortgage.

          SECTION 2. The Bonds of the Third 2003 Series and the Trustee's
Certificate shall be substantially in the following forms respectively:


                                       -6-

<PAGE>   7





                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                     FIRST MORTGAGE BOND, 6% SERIES DUE 2003

No. .............                                                   $100,000,000

          ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to Harris Trust and Savings Bank as
trustee (the "New Mortgage Trustee") under the Company's General Mortgage
Indenture and Deed of Trust dated as of November 1, 1992 (the "New Mortgage") or
its registered assigns, the principal sum of One Hundred Million Dollars
($100,000,000) on September 15, 2003, in any coin or currency of the United
States of America which at the time of payment is legal tender for public and
private debts, and to pay interest thereon in like coin or currency from
September 16, 1998, payable semi-annually on March 15 and September 15 in each
year, commencing March 15, 1999, at the rate of SIX PER CENT (6%) per annum,
until the Company's obligation with respect to the payment of such principal
shall be discharged as provided in the Indenture. Both the principal of, and the
interest on, this Bond are payable at the agency of the Company in the City of
Chicago, Illinois.

          This First Mortgage Bond shall not be entitled to any benefit under
the Indenture or any indenture supplemental thereto, or become valid or
obligatory for any purpose, until the form of certificate endorsed hereon shall
have been signed by or on behalf of Harris Trust and Savings Bank, the Trustee
under the Indenture, or a successor trustee thereto under the Indenture (the
"Trustee").

          The provisions of this First Mortgage Bond are continued on the
reverse hereof and such continued provisions shall for all purposes have the
same effect as though fully set forth at this place.

          IN WITNESS WHEREOF, Illinois Power Company has caused this First
Mortgage Bond to be signed (manually or by facsimile signature) in its name by
its President or a Vice President, and its corporate seal (or a facsimile
thereof) to be hereto affixed and attested (manually or by facsimile signature)
by its Secretary or an Assistant Secretary.


Dated . . . . . . . . . . . . .                        ILLINOIS POWER COMPANY,


                                                       By  . . . . . . . . . . .
                                                            Vice President

ATTEST:


 . . . . . . . . . . . . . . . .
       Assistant Secretary


                                       -7-

<PAGE>   8




                         [FORM OF TRUSTEE'S CERTIFICATE]

          This First Mortgage Bond is one of the Bonds of the series designated
therein, described in the within-mentioned Indenture and the Supplemental
Indenture dated as of September 15, 1998.


                                                  HARRIS TRUST AND SAVINGS BANK,
                                                                        Trustee,

                                                  By . . . . . . . . . . . . . .
                                                         Authorized Officer

                            [FORM OF REVERSE OF BOND)

          This First Mortgage Bond is one of a duly authorized issue of Bonds of
the Company (the "Bonds") in unlimited aggregate principal amount, of the series
hereinafter specified, all issued and to be issued under and equally secured by
the Mortgage and Deed of Trust (the "Indenture"), dated November 1, 1943,
executed by the Company to Harris Trust and Savings Bank (the "Trustee"), as
Trustee, to which Indenture and all indentures supplemental thereto, including
the Supplemental Indenture dated February 15, 1993, which amended Section 1 of
Article IX of the Indenture, reference is hereby made for a description of the
properties mortgaged and pledged, the nature and extent of the security, the
rights of the registered owners of the Bonds and of the Trustee in respect
thereof, and the terms and conditions upon which the Bonds are, and are to be,
secured. The Bonds may be issued in series, for various principal sums, may
mature at different times, may bear interest at different rates and may
otherwise vary as in the Indenture provided. This First Mortgage Bond is one of
a series designated as the First Mortgage Bonds, 6% Series Due 2003 (the "Bonds
of the Third 2003 Series") of the Company, unlimited in aggregate principal
amount, issued under and secured by the Indenture and described in the
supplemental indenture dated as of September 15, 1998 (the "Supplemental
Indenture of September 15, 1998"), between the Company and the Trustee,
supplemental to the Indenture.

          To the extent permitted by, and as provided in, the Indenture,
modifications or alterations of the Indenture, or of any indenture supplemental
thereto, and of the rights and obligations of the Company and of the holders of
the Bonds and coupons may be made with the consent of the Company by an
affirmative vote of the holders of not less than 662/3% in amount of the Bonds
entitled to vote then outstanding, at a meeting of Bondholders called and held
as provided in the Indenture, and by an affirmative vote of the holders of not
less than 662/3% in amount of the Bonds of any series entitled to vote then
outstanding and affected by such modification or alteration, in case one or more
but less than all of the series of Bonds then outstanding under the Indenture
are so affected; provided however, that no such modification or alteration shall
be made which will affect the terms of payment of the principal of, or interest
or premium, if any, on this First Mortgage Bond.




                                       -8-

<PAGE>   9







          In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the Bonds at any such time outstanding under the Indenture
may be declared or may become due and payable, upon the conditions and in the
manner and with the effect provided in the Indenture. The Indenture provides
that such declaration may in certain events be rescinded by the holders of a
majority in principal amount of the Bonds outstanding.

          No recourse shall be had for the payment of the principal of, or
premium or interest on this First Mortgage Bond, or for any claim based hereon
or on the Indenture or any indenture supplemental thereto, against any
incorporator, or against any stockholder, director or officer, as such, past,
present or future, of the Company, or of any predecessor or successor
corporation, either directly or through the Company or any such predecessor or
successor corporation, whether by virtue of any constitution, statute or rule of
law, or by the enforcement of any assessment or penalty or otherwise, all such
liability, whether at common law, in equity, by any constitution, statute, rule
of law, or otherwise, of incorporators, stockholders, directors or officers
being released by every owner hereof by the acceptance of this First Mortgage
Bond and as part of the consideration for the issue hereof, and being likewise
released by the terms of the Indenture; provided, however, that nothing herein
or in the Indenture or any indenture supplemental thereto contained shall
prevent the enforcement of the liability, if any, of any stockholder or
subscriber to capital stock upon or in respect of shares of capital stock not
fully paid up.

          Notwithstanding any provision in the Indenture, the Supplemental
Indenture of September 15, 1998 or this First Mortgage Bond to the contrary, any
payment by the Company under the New Mortgage of principal of, or interest on,
bonds which shall have been authenticated and delivered under the New Mortgage
(the "New Mortgage Bonds of the Second 2003 Series") upon the basis of the
issuance and delivery to the New Mortgage Trustee of the Bonds of the Third 2003
Series shall, to the extent thereof, be deemed to satisfy and discharge the
obligation of the Company to make a payment of principal or interest, as the
case may be, in respect of this First Mortgage Bond which is then due.

          This First Mortgage Bond constitutes a "Pledged Bond" (as defined in
the New Mortgage) and is subject to all of the rights and restrictions
applicable to Pledged Bonds as set forth in the New Mortgage. Without limiting
the generality of the foregoing, this First Mortgage Bond shall be subject to
surrender by the New Mortgage Trustee in accordance with the provisions of
Section 7.03 of the New Mortgage. To the extent that any provisions in the
Indenture, the Supplemental Indenture of September 15, 1998 or this First
Mortgage Bond are inconsistent with the provisions relating to Pledged Bonds
that are set forth in the New Mortgage, the provisions of the New Mortgage shall
apply.

          SECTION 3. Notwithstanding any provision in the Original Indenture,
this Supplemental Indenture, or the Bonds of the Third 2003 Series to the
contrary, any payment by the Company under


                                       -9-

<PAGE>   10




the New Mortgage of principal of, or interest on, New Mortgage Bonds of the
Second 2003 Series upon the basis of the issuance and delivery to the New
Mortgage Trustee of the Bonds of the Third 2003 Series shall, to the extent
thereof, be deemed to satisfy and discharge the obligation of the Company to
make any payment of principal or interest, as the case may be, in respect of the
Bonds of the Third 2003 Series which is then due.

          SECTION 4. The Bonds of the Third 2003 Series constitute "Pledged
Bonds" (as defined in the New Mortgage) and are subject to all of the rights and
restrictions applicable to Pledged Bonds as set forth in the New Mortgage.
Without limiting the generality of the foregoing, the Bonds of the Third 2003
Series shall be subject to surrender by the New Mortgage Trustee in accordance
with the provisions of Section 7.03 of the New Mortgage. To the extent that any
provisions in the Original Indenture, this Supplemental Indenture or the Bonds
of the Third 2003 Series are inconsistent with the provisions relating to
Pledged Bonds that are set forth in the New Mortgage, the provisions of the New
Mortgage shall apply.


                                   ARTICLE II.

                    ISSUE OF BONDS OF THE THIRD 2003 SERIES.

          SECTION 1. The Company hereby exercises the right to obtain the
authentication of $100,000,000 principal amount of additional Bonds pursuant to
the terms of Section 4 of Article III of the Original Indenture on the basis of
75% of the net bondable value of property additions not subject to an unfunded
prior lien. All such additional Bonds shall be Bonds of the Third 2003 Series.

          SECTION 2. Such Bonds of the Third 2003 Series may be authenticated
and delivered prior to the filing for recordation of this Supplemental
Indenture.

          SECTION 3. Notwithstanding any provision in the Original Indenture to
the contrary, execution of the Bonds of the Third 2003 Series on behalf of the
Company, and the attesting of the corporate seal of the Company affixed to the
Bonds of the Third 2003 Series by the officers of the Company authorized to do
such acts by Section 12 of Article II of the Original Indenture may be validly
done either by the manual or the facsimile signatures of such authorized
officers of the Company.


                                  ARTICLE III.

                                   REDEMPTION.

        The Bonds of the Third 2003 Series shall not be redeemable prior to
maturity.



                                      -10-

<PAGE>   11




                                   ARTICLE IV.

                                  THE TRUSTEE.

        The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Original
Indenture set forth and upon the following terms and conditions:

               The Trustee shall not be responsible in any manner whatsoever for
        or in respect of the validity or sufficiency of this Supplemental
        Indenture or the due execution hereof by the Company or for or in
        respect of the recitals contained herein, all of which recitals are made
        by the Company solely. In general, each and every term and condition
        contained in Article XIII of the Original Indenture shall apply to this
        Supplemental Indenture with the same force and effect as if the same
        were herein set forth in full, with such omissions, variations and
        modifications thereof as may be appropriate to make the same conform to
        this Supplemental Indenture.


                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

        This Supplemental Indenture may be simultaneously executed in any number
of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.




                                      -11-

<PAGE>   12




        IN WITNESS WHEREOF, Illinois Power Company has caused this Supplemental
Indenture to be executed on its behalf by its Chairman and President, one of its
Executive Vice Presidents, one of its Senior Vice Presidents or one of its Vice
Presidents and its corporate seal to be hereto affixed and said seal and this
Supplemental Indenture to be attested by its Secretary or one of its Assistant
Secretaries; and said Harris Trust and Savings Bank, in evidence of its
acceptance of the trust hereby created, has caused this Supplemental Indenture
to be executed on its behalf by its President or one of its Vice Presidents and
its corporate seal to be hereto affixed and said seal and this Supplemental
Indenture to be attested by its Secretary or one of its Assistant Secretaries;
all as of the fifteenth day of August, 1998.


                                             ILLINOIS POWER COMPANY



                                             By   /s/ ROBERT A. SCHULTZ 
                                               ---------------------------------
                                                      Robert A. Schultz
                                                      Vice President - Finance


(CORPORATE SEAL)


ATTEST:


/s/ SONDRA K. COOPRIDER        
- -------------------------------
Sondra K. Cooprider
Assistant Secretary

                                          HARRIS TRUST AND SAVINGS BANK, Trustee



                                             By    /s/ J. BARTOLINI             
                                                --------------------------------
                                                       J. Bartolini
                                                       Vice President

(CORPORATE SEAL)

ATTEST:



/s/ C. POTTER                                        
- -----------------------------
C. Potter
Assistant Secretary


                                      -12-

<PAGE>   13




STATE OF ILLINOIS             )
                              ) SS.:
COUNTY OF MACON               )

        BE IT REMEMBERED, that on this 12th day of August, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President - Finance and Sondra K.
Cooprider, Assistant Secretary, of Illinois Power Company, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be such officers, and who are personally known
to me to be the same persons who executed as such officers the within instrument
of writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such officers
and as the free and voluntary act of said Illinois Power Company for the uses
and purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                           -------------------------------------
                                           Notary Public, Macon County, Illinois


My Commission Expires on _________________.

(NOTARIAL SEAL)


STATE OF ILLINOIS             )
                              ) SS.:
COUNTY OF COOK                )

        BE IT REMEMBERED, that on this 17th day of August, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President, and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such Vice President and Secretary, respectively, and as the
free and voluntary act of said Harris Trust and Savings Bank for the uses and
purposes therein set forth.

        IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.




                                           -------------------------------------
                                           Notary Public, Macon County, Illinois


My Commission Expires on May 21, 2001.

(NOTARIAL SEAL)


                                      -13-

<PAGE>   14







        Return To:                              This Instrument Was Prepared By:

        ILLINOIS POWER COMPANY                  SCHIFF HARDIN & WAITE
        Real Estate Dept. F-14                  6600 Sears Tower
        500 S. 27th Street                      233 South Wacker Drive
        Decatur, IL 62525                       Chicago, IL  60606




                                      -14-

<PAGE>   1
                                                                    EXHIBIT 4.46

================================================================================

                             ILLINOIS POWER COMPANY

                                       TO

                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE

                               ------------------


                             SUPPLEMENTAL INDENTURE

                         DATED AS OF SEPTEMBER 15, 1998

                                       TO

                  GENERAL MORTGAGE INDENTURE AND DEED OF TRUST

                          DATED AS OF NOVEMBER 1, 1992

================================================================================
<PAGE>   2

SUPPLEMENTAL INDENTURE dated as of September 15, 1998 (the "Supplemental
Indenture"), made by and between ILLINOIS POWER COMPANY, a corporation organized
and existing under the laws of the State of Illinois (the "Company"), party of
the first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the General Mortgage indenture and Deed of Trust dated as of November 1,
1992, hereinafter mentioned, party of the second part;

         WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 (the
"Indenture"), to the Trustee, for the security of the Bonds of the Company
issued and to be issued thereunder (the "Bonds"); and

         WHEREAS, pursuant to the terms and provisions of the Indenture there
were created and authorized by Supplemental Indentures thereto bearing the
following dates, respectively, the New Mortgage Bonds of the series issued
thereunder and respectively identified opposite such dates:
<TABLE>
<CAPTION>

 DATE OF SUPPLEMENTAL              IDENTIFICATION
      INDENTURE                       OF SERIES                         CALLED
- --------------------              ------------------                    ------

<S>                             <C>                                   <C>        
February 15, 1993                 8% Series due 2023                  Bonds of the 2023 Series
March 15, 1993                   6 1/2% Series due 2000               Bonds of the 2000 SeriES
March 15, 1993                   6 3/4% Series due 2005               Bonds of the 2005 SeriES
July 15, 1993                    7 1/2% Series due 2025               Bonds of the 2025 SeriES
August 1, 1993                   6 1/2% Series due 2003               Bonds of the First 2003 Series
October 15, 1993                  5 % Series due 2000                 Bonds of the Second 2000 Series            
November 1, 1993                 Pollution Control Series M           Bonds of the Pollution Control Series M    
November 1, 1993                 Pollution Control Series N           Bonds of the Pollution Control Series N    
November 1, 1993                 Pollution Control Series O           Bonds of the Pollution Control Series O    
April 1, 1997                    Pollution Control Series P           Bonds of the Pollution Control Series P    
April 1, 1997                    Pollution Control Series Q           Bonds of the Pollution Control Series Q 
April 1, 1997                    Pollution Control Series R           Bonds of the Pollution Control Series R  
March 1, 1998                    Pollution Control Series S           Bonds of the Pollution Control Series S    
March 1, 1998                    Pollution Control Series T           Bonds of the Pollution Control Series T    
July 15, 1998                    6 1/4% Series due 2002               Bonds of the 2002 Series

</TABLE>

         WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Indenture, to be known as New Mortgage Bonds, 6% Series due
2003 (the "New Mortgage Bonds of the Second 2003 Series"); and

         WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the indenture, and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and determined to make, execute and deliver to the Trustee a Supplemental
Indenture in the form hereof for the purposes herein provided; and

         WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

         THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of 



                                       2
<PAGE>   3
One Dollar to it duly paid by the Trustee at or before the ensealing and
delivery of these presents, the receipt whereof is hereby acknowledged, hereby
covenants and agrees to and with the Trustee and its successors in the trust
under the Indenture, for the benefit of those who shall hold the Bonds as
follows:


                                   ARTICLE I.

          DESCRIPTION OF NEW MORTGAGE BONDS OF THE SECOND 2003 SERIES.

         SECTION 1. The Company hereby creates a new series of Bonds to be known
as the "New Mortgage Bonds of the Second 2003 Series." The New Mortgage Bonds of
the Second 2003 Series shall be executed, authenticated and delivered in
accordance with the provisions of, and shall in all respects be subject to, all
of the terms, conditions and covenants of the Indenture, as supplemented and
modified.

         The commencement of the first interest period shall be September 16,
1998. All New Mortgage Bonds of the Second 2003 Series shall mature on September
15, 2003, and shall bear interest at the rate of SIX PER CENT (6%) per annum,
payable semi-annually on March 15 and September 15 in each year. The person in
whose name any of the New Mortgage Bonds of the Second 2003 Series are
registered at the close of business on any record date (as hereinafter defined)
with respect to any interest payment date shall be entitled to receive the
interest payable on such interest payment date notwithstanding the cancellation
of such New Mortgage Bonds of the Second 2003 Series upon any transfer or
exchange subsequent to the record date and prior to such interest payment date;
provided, however, that if and to the extent the Company shall default in the
payment of the interest due on such interest payment date, such defaulted
interest shall be paid as provided in Section 3.07 of the Indenture.

         The term "record date" as used in this Section with respect to any
interest payment date shall mean the March 1 or September 1, as the case may be,
next preceding the semi-annual interest payment date, or, if such March 1 or
September 1 shall be a legal holiday or a day on which banking institutions in
the City of Chicago, Illinois, are authorized by law to close, then the next
preceding day which shall not be a legal holiday or a day on which such
institutions are so authorized to close.

         SECTION 2. The New Mortgage Bonds of the Second 2003 Series shall be
issued only as registered Bonds without coupons of the denomination of $1,000,
or any integral multiple of $1,000, appropriately numbered. The New Mortgage
Bonds of the Second 2003 Series may be exchanged, upon surrender thereof, at the
agency of the Company in the City of Chicago, Illinois, for one or more New
Mortgage Bonds of the Second 2003 Series of other authorized denominations, for
the same aggregate principal amount, subject to the terms and conditions set
forth in the Indenture.

         New Mortgage Bonds of the Second 2003 Series may be exchanged or
transferred without expense to the registered owner thereof except that any
taxes or other governmental charges required to be paid with respect to such
transfer or exchange shall be paid by the registered owner requesting such
transfer or exchange as a condition precedent to the exercise of such privilege.

         SECTION 3. The New Mortgage Bonds of the Second 2003 Series and the
Trustee's Certificate of Authentication shall be substantially in the following
forms respectively:


                                       3
<PAGE>   4
                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                      NEW MORTGAGE BOND, 6% SERIES DUE 2003

No. . . . . . . . . . . . . .                                      $100,000,000

         ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company," which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to ........ or registered assigns, the
principal sum of One Hundred Million Dollars ($100,000,000) on September 15,
2003, in any coin or currency of the United States of America which at the time
of payment is legal tender for public and private debts, and to pay interest
thereon in like coin or currency from September 16, 1998, payable semi-annually
on March 15 and September 15 in each year, commencing March 15, 1999, at the
rate of SIX PER CENT (6%) per annum, until the Company's obligation with respect
to the payment of such principal shall be discharged as provided in the
Indenture hereinafter mentioned. The interest so payable on any March 15 or
September 15 will, subject to certain exceptions provided in the Supplemental
Indenture dated as of September 15, 1998, be paid to the person in whose name
this New Mortgage Bond is registered at the close of business on the immediately
preceding March 1 or September 1, as the case may be. Both principal of, and
interest on, this New Mortgage Bond are payable at the agency of the Company in
the City of Chicago, Illinois.

         This New Mortgage Bond shall not be entitled to any benefit under the
Indenture or any indenture supplemental thereto, or become valid or obligatory
for any purpose, until the form of certificate endorsed hereon shall have been
signed by or on behalf of Harris Trust and Savings Bank, the Trustee under the
Indenture, or a successor trustee thereto under the Indenture (the "Trustee").

         The provisions of this New Mortgage Bond are continued on the reverse
hereof and such continued provisions shall for all purposes have the same effect
as though fully set forth at this place.

         IN WITNESS WHEREOF, Illinois Power Company has caused this New Mortgage
Bond to be signed (manually or by facsimile signature) in its name by an
Authorized Executive Officer, as defined in the Indenture, and its corporate
seal (or a facsimile thereof) to be hereto affixed and attested (manually or by
facsimile signature) by an Authorized Executive Officer, as defined in the
Indenture.

Dated  . . . . . . . . . . . .                ILLINOIS POWER COMPANY,


                                              By ...............................
                                                   Authorized Executive Officer

ATTEST:

 ......................................
    Authorized Executive Officer



                                       4
<PAGE>   5

                [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

         This New Mortgage Bond is one of the Bonds of the series designated
therein referred to in the within-mentioned Indenture dated as of November 1,
1992 and the Supplemental Indenture dated as of September 15, 1998.


                                               HARRIS TRUST AND SAVINGS BANK,
                                                                  Trustee,


                                               By...............................
                                                       Authorized Signatory


                            [FORM OF REVERSE OF BOND]

         This New Mortgage Bond is one of a duly authorized issue of Bonds of
the Company (the "Bonds") in unlimited aggregate principal amount, of the series
hereinafter specified, all issued and to be issued under and equally secured by
a General Mortgage Indenture and Deed of Trust (the "Indenture"), dated as of
November 1, 1992, executed by the Company to Harris Trust and Savings Bank (the
"Trustee"), as Trustee, to which Indenture and all indentures supplemental
thereto reference is hereby made for a description of the properties mortgaged
and pledged, the nature and extent of the security, the rights of registered
owners of the Bonds and of the Trustee in respect thereof, and the terms and
conditions upon which the Bonds are, and are to be, secured. The Bonds may be
issued in series, for various principal sums, may mature at different times, may
bear interest at different rates and may otherwise vary as provided in the
Indenture. This New Mortgage Bond of the Second 2003 Series is one of a series
designated as the "New Mortgage Bonds, 6% Series Due 2003" (the "New Mortgage
Bonds of the Second 2003 Series") of the Company, unlimited in aggregate
principal amount, issued under and secured by the Indenture and described in the
supplemental indenture dated as of September 15, 1998 (the "Supplemental
Indenture dated as of September 15, 1998"), between the Company and the Trustee,
supplemental to the Indenture.

         The New Mortgage Bonds of the Second 2003 Series are not subject to
redemption prior to maturity.

         In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the Bonds at any such time outstanding under the Indenture
may be declared or may become due and payable, upon the conditions and in the
manner and with the effect provided in the Indenture. The Indenture provides
that such declaration may be rescinded under certain circumstances.


                                  ARTICLE II.

             ISSUE OF NEW MORTGAGE BONDS OF THE SECOND 2003 SERIES.

         SECTION 1. The Company hereby exercises the right to obtain the
authentication of $100,000,000 principal amount of Bonds pursuant to the terms
of Section 4.02 of the Indenture. All such Bonds shall be New Mortgage Bonds of
the Second 2003 Series.



                                       5
<PAGE>   6

         SECTION 2. Such New Mortgage Bonds of the Second 2003 Series may be
authenticated and delivered prior to the filing for recordation of this
Supplemental Indenture.

                                  ARTICLE III.

                                   REDEMPTION.

         The New Mortgage Bonds of the Second 2003 Series shall not be
redeemable prior to maturity.

                                   ARTICLE IV.

                                  THE TRUSTEE.

         The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:

                  The Trustee shall not be responsible in any manner whatsoever
         for or in respect of the validity or sufficiency of this Supplemental
         Indenture or the due execution hereof by the Company or for or in
         respect of the recitals contained herein, all of which recitals are
         made by the Company solely. In general, each and every term and
         condition contained in Article Eleven of the Indenture shall apply to
         this Supplemental Indenture with the same force and effect as if the
         same were herein set forth in full, with such omissions, variations and
         modifications thereof as may be appropriate to make the same conform to
         this Supplemental Indenture.

                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

         This Supplemental Indenture may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.




                                       6
<PAGE>   7


         IN WITNESS WHEREOF, Illinois Power Company has caused this Indenture to
be executed on its behalf by an Authorized Executive Officer as defined in the
Indenture, and its corporate seal to be hereto affixed and said seal and this
Indenture to be attested by an Authorized Executive Officer as defined in the
Indenture; and said Harris Trust and Savings Bank, in evidence of its acceptance
of the trust hereby created, has caused this Indenture to be executed on its
behalf by its President or one of its Vice Presidents and its corporate seal to
be hereto affixed and said seal and this Indenture to be attested by its
Secretary or one of its Assistant Secretaries; all as of the fifteenth day of
September, 1998.

                                        ILLINOIS POWER COMPANY


                                        By /s/ ROBERT A. SCHULTZ      
                                           ----------------------------
(CORPORATE SEAL)                               Robert A. Schultz
                                               Vice President - Finance


ATTEST:


/s/ SONDRA K. COOPRIDER
- -----------------------
Sondra K. Cooprider
Assistant Secretary



                                        HARRIS TRUST AND SAVINGS BANK, TRUSTEE


                                        By /s/ J. BARTOLINI 
                                           -------------------------------
(CORPORATE SEAL)                               J. Bartolini
                                               Vice President


ATTEST:


/s/ C. POTTER
- -----------------------
C. Potter
Assistant Secretary






                                       7
<PAGE>   8



STATE OF ILLINOIS )
                  )  SS.:
COUNTY OF MACON   )

         BE IT REMEMBERED, that on this 12th day of August, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Robert A. Schultz, Vice President - Finance and Sondra K.
Cooprider, Assistant Secretary, of Illinois Power Company, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be such officers, and who are personally known
to me to be the same persons who executed as such officers the within instrument
of writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such officers,
and as the free and voluntary act of said Illinois Power Company for the uses
and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.



                                     __________________________________________
                                     Notary Public, Macon County, Illinois

My Commission Expires _______________.
(NOTARIAL SEAL)



STATE OF ILLINOIS )
                  ) SS.:
COUNTY OF COOK    )

         BE IT REMEMBERED, that on this 17th day of August, 1998, before me, the
undersigned Marianne Tinerella, a Notary Public within and for the County and
State aforesaid, personally came J. Bartolini, Vice President and C. Potter,
Assistant Secretary, of Harris Trust and Savings Bank, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be the same persons who executed as such
officers the within instrument of writing, and such persons duly acknowledged
that they signed, sealed and delivered the said instrument as their free and
voluntary act as such officers, and as the free and voluntary act of said Harris
Trust and Savings Bank for the uses and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.


                                     __________________________________________
                                      Notary Public, Cook County, Illinois

My Commission Expires: May 21, 2001

(NOTARIAL SEAL)



                                       8
<PAGE>   9
Return To:                                     This Instrument Was Prepared By:

         ILLINOIS POWER COMPANY                      SCHIFF HARDIN & WAITE
         Real Estate Dept. F-14                      6600 Sears Tower
         500 S. 27th Street                          233 South Wacker Drive
         Decatur, IL 62525                           Chicago, IL 60606




















                                       9

<PAGE>   1
                                                                    EXHIBIT 4.47
================================================================================
                             ILLINOIS POWER COMPANY

                                       TO

                         HARRIS TRUST AND SAVINGS BANK,

                                   AS TRUSTEE





                             SUPPLEMENTAL INDENTURE

                           DATED AS OF OCTOBER 1, 1998


                                       TO


                  GENERAL MORTGAGE INDENTURE AND DEED OF TRUST

                          DATED AS OF NOVEMBER 1, 1992

================================================================================
<PAGE>   2


SUPPLEMENTAL INDENTURE, dated as of October 1, 1998 (the "Supplemental
Indenture"), made by and between ILLINOIS POWER COMPANY, a corporation organized
and existing under the laws of the State of Illinois (the "Company"), party of
the first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the General Mortgage Indenture and Deed of Trust dated as of November 1,
1992, hereinafter mentioned, party of the second part;

         WHEREAS, Illinois Development Finance Authority, a political
subdivision and body politic and corporate, duly organized and validly existing
under and by virtue of the Constitution and laws of the State of Illinois
("IDFA") issued its Adjustable Rate Pollution Control Revenue Refunding Bonds in
the aggregate principal amount of $111,770,000 in three series consisting of (i)
$51,770,000 aggregate principal amount of Adjustable Rate Pollution Control
Revenue Refunding Bonds, 1993 Series A (Illinois Power Company Project) (the
"Series A IDFA Bonds"), (ii) $30,000,000 aggregate principal amount of
Adjustable Rate Pollution Control Revenue Refunding Bonds, 1993 Series B
(Illinois Power Company Project) (the "Series B IDFA Bonds"), and (iii)
$30,000,000 aggregate principal amount of Adjustable Rate Pollution Control
Revenue Refunding Bonds, 1993 Series C (Illinois Power Company Project) (the
"Series C IDFA Bonds") (the Series A IDFA Bonds, Series B IDFA Bonds and Series
C IDFA Bonds shall collectively be referred to as the "Related IDFA Bonds") and
lent the proceeds of the issuance of the Related IDFA Bonds to the Company
pursuant to three separate Loan Agreements each dated as of November 1, 1993
(individually as from time to time amended or modified, a "Loan Agreement" and
collectively, the "Loan Agreements"), to assist the Company in the refunding of
certain prior IDFA Pollution Control Revenue Bonds on or about December 15,
1993.

         WHEREAS, the Series A IDFA Bonds, Series B IDFA Bonds and Series C IDFA
Bonds were issued by IDFA pursuant to three separate Indentures of Trust (as
from time to time amended or modified, the "IDFA Series A Indenture," the "IDFA
Series B Indenture" and the "IDFA Series C Indenture," respectively), each dated
as of November 1, 1993 between IDFA and The Chase Manhattan Bank (formerly known
as Chemical Bank) as Trustee under each such Indenture (together with any
successor in such capacity, the "IDFA Indenture Trustee"), each of which was
initially secured by three separate letters of credit (as from time to time
amended, modified or replaced, the "Series A Letter of Credit," the "Series B
Letter of Credit" and the "Series C Letter of Credit," respectively, and
collectively, the "Letters of Credit") from Canadian Imperial Bank of Commerce,
acting by and through its New York Agency ("CIBC") issued pursuant to three
separate Reimbursement Agreements dated as of November 1, 1993 between the
Company and CIBC (as from time to time amended or modified, the "Series A
Reimbursement Agreement," the "Series B Reimbursement Agreement" and the "Series
C Reimbursement Agreement," respectively, and collectively, the "Reimbursement
Agreements"); and

         WHEREAS, the Series A Letter of Credit allows the IDFA Indenture
Trustee to draw up to $54,535,795 for payment of principal and interest on the
Series A IDFA Bonds (the "Series A Stated Amount"), the Series B Letter of
Credit allows the IDFA Indenture Trustee to draw up to 


                                      -2-
<PAGE>   3
$31,602,740 for payment of principal and interest on the Series B IDFA Bonds
(the "Series B Stated Amount"), and the Series C Letter of Credit allows the
IDFA Indenture Trustee to draw up to $31,602,740 for payment of principal and
interest on the Series C IDFA Bonds (the "Series C Stated Amount");

         WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 as from time
to time amended (the "Indenture"), to the Trustee, for the security of the Bonds
of the Company issued and to be issued thereunder (the "Bonds"); and

         WHEREAS, the Company created three new series of Bonds under the
Indenture and a Supplemental Indenture dated as of November 1, 1993 (the
"November 1, 1993 Supplemental Indenture") known as New Mortgage Bonds,
Pollution Control Series M (the "Pollution Control Series M Bonds"), New
Mortgage Bonds, Pollution Control Series N (the "Pollution Control Series N
Bonds") and the New Mortgage Bonds, Pollution Control Series O (the "Pollution
Control Series O Bonds") to secure its obligations under the Reimbursement
Agreements;

         WHEREAS, effective as of November 10, 1998, the Letters of Credit will
be replaced by three separate letters of credit (as from time to time amended,
modified or replaced, the "Series A ABN AMRO Letter of Credit," the "Series B
ABN AMRO Letter of Credit," and the "Series C ABN AMRO Letter of Credit,"
respectively, and collectively, the "ABN AMRO Letters of Credit") from ABN AMRO
Bank N.V. ("ABN AMRO") issued pursuant to three separate Reimbursement
Agreements dated as of October 1, 1998 between the Company and ABN AMRO (as from
time to time amended or modified, the "Series A ABN AMRO Reimbursement
Agreement," the "Series B ABN AMRO Reimbursement Agreement" and the "Series C
ABN AMRO Reimbursement Agreement," respectively, and collectively, the "ABN AMRO
Reimbursement Agreements");

         WHEREAS, the Company, with the consent of CIBC and the Trustee, desires
to amend the November 1, 1993 Supplemental Indenture to reflect that, effective
as of November 10, 1998, the Letters of Credit will be replaced by the ABN AMRO
Letters of Credit and that the Pollution Control Series M Bonds, the Pollution
Control Series N Bonds and Pollution Control Series O Bonds will hereafter
secure the Company's obligations under the Reimbursement Agreements and the ABN
AMRO Reimbursement Agreements;

         WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the Indenture, and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and determined to make, execute and deliver to the Trustee a Supplemental
Indenture in the form hereof for the purposes herein provided; and

         WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;



                                      -3-
<PAGE>   4

         NOW, THEREFORE, THIS SUPPLEMENTAL INDENTURE WITNESSETH:

         THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of One Dollar to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, hereby covenants and agrees to and with the Trustee and
its successors in the trust under the Indenture, for the benefit of those who
shall hold the Bonds as follows:

                                   ARTICLE I.

            AMENDMENT OF THE NOVEMBER 1, 1993 SUPPLEMENTAL INDENTURE.

         SECTION 1. The November 1, 1993 Supplemental Indenture is hereby
amended to provide that, effective as of November 10, 1998:

         (a) All references to the "Series A Letter of Credit" shall also be
deemed to be references to the "Series A ABN AMRO Letter of Credit (or any
successor letter of credit)";

         (b) All references to the "Series B Letter of Credit" shall also be
deemed to be references to the "Series B ABN AMRO Letter of Credit (or any
successor letter of credit)";

         (c) All references to the "Series C Letter of Credit" shall also be
deemed to be references to the "Series C ABN AMRO Letter of Credit (or any
successor letter of credit)";

         (d) All references to the "Series A Reimbursement Agreement" shall also
be deemed to be references to the "Series A ABN AMRO Reimbursement Agreement (or
any successor reimbursement agreement)";

         (e) All references to the "Series B Reimbursement Agreement" shall also
be deemed to be references to the "Series B ABN AMRO Reimbursement Agreement (or
any successor reimbursement agreement)";

         (f) All references to the "Series C Reimbursement Agreement" shall also
be deemed to be references to the "Series C ABN AMRO Reimbursement Agreement (or
any successor reimbursement agreement)"; and

         (g) All references to "CIBC" in Articles I, II and III of the November
1, 1993 Supplemental Indenture shall also be deemed to be references to "ABN
AMRO (or any successor letter of credit bank)".



                                      -4-
<PAGE>   5

                                  ARTICLE II.

                                  THE TRUSTEE.

         The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:

         The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Supplemental Indenture or the due
execution hereof by the Company or for or in respect of the recitals contained
herein, all of which recitals are made by the Company solely. In general, each
and every term and condition contained in Article Eleven of the Indenture shall
apply to this Supplemental Indenture with the same force and effect as if the
same were herein set forth in full, with such omissions, variations and
modifications thereof as may be appropriate to make the same conform to this
Supplemental Indenture.

                                  ARTICLE III.

                            MISCELLANEOUS PROVISIONS.

         This Supplemental Indenture may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.






                                      -5-
<PAGE>   6

         IN WITNESS WHEREOF, said Illinois Power Company has caused this
Supplemental Indenture to be executed on its behalf by an Authorized Executive
Officer as defined in the Indenture, and its corporate seal to be hereto affixed
and said seal and this Supplemental Indenture to be attested by an Authorized
Executive Officer as defined in the Indenture; and said Harris Trust and Savings
Bank, in evidence of its acceptance of the trust hereby created, has caused this
Supplemental Indenture to be executed on its behalf by its President or one of
its Vice Presidents and its corporate seal to be hereto affixed and said seal
and this Supplemental Indenture to be attested by its Secretary or one of its
Assistant Secretaries; all as of the first day of October, 1998.

                                       ILLINOIS POWER COMPANY

                                       By   /s/ Eric B. Weekes
                                          _____________________________
                                            Eric B. Weekes
                                            Treasurer



(CORPORATE SEAL)


ATTEST:

  /s/ Sondra Cooprider
______________________________________
   Sondra Cooprider
   Assistant Corporate Secretary


                                       HARRIS TRUST AND SAVINGS BANK, Trustee

                                       By    /s/ J. Bartolini
                                           _____________________________
                                            J. Bartolini
                                            Vice President


(CORPORATE SEAL)


ATTEST:

  /s/ D. Donovan
______________________________________
D. Donovan
Assistant Secretary




                                      -6-
<PAGE>   7
STATE OF ILLINOIS          )
COUNTY OF MACON            )ss.:

         BE IT REMEMBERED, that on this 1st day of October, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came Eric B. Weekes, Treasurer, and Sondra Cooprider, Assistant
Corporate Secretary, of Illinois Power Company, a corporation duly organized,
incorporated and existing under the laws of the State of Illinois, who are
personally known to me to be such officers, and who are personally known to me
to be the same persons who executed as such officers the within instrument of
writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such officers
and as the free and voluntary act of said Illinois Power Company for the uses
and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.

                                          ______________________________________
                                          Notary Public, Macon County, Illinois

My Commission Expires on ________________.

(NOTARIAL SEAL)



STATE OF ILLINOIS          )
COUNTY OF COOK             )ss.:

         BE IT REMEMBERED, that on this 2nd day of October, 1998, before me, the
undersigned, a Notary Public within and for the County and State aforesaid,
personally came J. Bartolini, Vice President, and D. Donovan, Assistant
Secretary, of Harris Trust and Savings Bank, a corporation duly organized,
incorporated and existing under the laws of the State of Illinois, who are
personally known to me to be the same persons who executed as such officers the
within instrument of writing, and such persons duly acknowledged that they
signed, sealed and delivered the said instrument as their free and voluntary act
as such officers, and as the free and voluntary act of said Harris Trust and
Savings Bank for the uses and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.:


                                          ______________________________________
                                           Notary Public, Cook County, Illinois
My Commission Expires on _______________.

(NOTARIAL SEAL)

                                      -7-
<PAGE>   8
Return To:                                     This Instrument Was Prepared By:
         ILLINOIS POWER COMPANY                     Schiff Hardin & Waite
         Real Estate Dept. F-14                     6600 Sears Tower
         500 S. 27th Street                         233 South Wacker Drive
         Decatur, IL 62525                          Chicago, IL 60606








                                      -8-

<PAGE>   1
                                                                    EXHIBIT 4.48
                                                (Form of Supplemental Indenture)

SUPPLEMENTAL INDENTURE, dated as of _____________, _______ (the "Supplemental
Indenture), made by and between ILLINOIS POWER COMPANY, a corporation organized
and existing under the laws of the State of Illinois (the "Company"), party of
the first part, and HARRIS TRUST AND SAVINGS BANK, a corporation organized and
existing under the laws of the State of Illinois (the "Trustee"), as Trustee
under the General Mortgage indenture and Deed of Trust dated as of November 1,
1992, hereinafter mentioned, party of the second part;

         WHEREAS, the Company has heretofore executed and delivered its General
Mortgage Indenture and Deed of Trust dated as of November 1, 1992 (the
"Indenture"), to the Trustee, for the security of the Bonds of the Company
issued and to be issued thereunder (the "Bonds"); and

         WHEREAS, pursuant to the terms and provisions of the Indenture there
were created and authorized by Supplemental Indentures thereto bearing the
following dates, respectively, the New Mortgage Bonds of the series issued
thereunder and respectively identified opposite such dates:

<TABLE>
<CAPTION>
  Date of Supplemental        Identification
       Indenture                 of Series                            Called
  --------------------        --------------                          ------
<S>                          <C>                          <C>        
    February 15, 1993                8% Series due 2023     Bonds of the 2023 Series
       March 15, 1993            6 1/2% Series due 2000     Bonds of the 2000 Series
       March 15, 1993            6 3/4% Series due 2005     Bonds of the 2005 Series
        July 15, 1993            7 1/2% Series due 2025     Bonds of the 2025 Series
       August 1, 1993            6 1/2% Series due 2003     Bonds of the 2003 Series
     October 15, 1993            5 5/8% Series due 2000     Bonds of the Second 2000 Series
     November 1, 1993        Pollution Control Series M     Bonds of the Pollution Control Series M
     November 1, 1993        Pollution Control Series N     Bonds of the Pollution Control Series N
     November 1, 1993        Pollution Control Series O     Bonds of the Pollution Control Series O
        April 1, 1997        Pollution Control Series P     Bonds of the Pollution Control Series P
        April 1, 1997        Pollution Control Series Q     Bonds of the Pollution Control Series Q
        April 1, 1997        Pollution Control Series R     Bonds of the Pollution Control Series R
        March 1, 1998        Pollution Control Series S     Bonds of the Pollution Control Series S
        March 1, 1998        Pollution Control Series T     Bonds of the Pollution Control Series T
        July 15, 1998            6 1/4% Series due 2002     Bonds of the 2002 Series
   September 15, 1998                6% Series due 2003     Bonds of the Second 2003 Series
</TABLE>

         WHEREAS, the Company desires to create a new series of Bonds to be
issued under the Indenture, to be known as New Mortgage Bonds, ____% Series due
____ (the "New Mortgage Bonds of the ____ Series"); and

         WHEREAS, the Company, in the exercise of the powers and authority
conferred upon and reserved to it under the provisions of the indenture, and
pursuant to appropriate resolutions of the Board of Directors, has duly resolved
and determined to make, execute and deliver to the Trustee a Supplemental
Indenture in the form hereof for the purposes herein provided; and
<PAGE>   2
         WHEREAS, all conditions and requirements necessary to make this
Supplemental Indenture a valid, binding and legal instrument have been done,
performed and fulfilled and the execution and delivery hereof have been in all
respects duly authorized;

         NOW, THEREFORE, THIS INDENTURE WITNESSETH:

         THAT Illinois Power Company, in consideration of the purchase and
ownership from time to time of the Bonds and the service by the Trustee, and its
successors, under the Indenture and of One Dollar to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, hereby covenants and agrees to and with the Trustee and
its successors in the trust under the Indenture, for the benefit of those who
shall hold the Bonds as follows:


                                   ARTICLE I.

              DESCRIPTION OF NEW MORTGAGE BONDS OF THE ____ SERIES.

         SECTION 1. The Company hereby creates a new series of Bonds to be known
as "New Mortgage Bonds of the ____ Series." The New Mortgage Bonds of the ____
Series shall be executed, authenticated and delivered in accordance with the
provisions of, and shall in all respects be subject to, all of the terms,
conditions and covenants of the Indenture, as supplemented and modified.

         The commencement of the first interest period shall be ___________,
______. All New Mortgage Bonds of the ____ Series shall mature _____________,
and shall bear interest at the rate of ______________ per cent (______%) per
annum, payable semi-annually on the first day of _________ and the first day of
___________ in each year. The person in whose name any of the New Mortgage Bonds
of the ____ Series are registered at the close of business on any record date
(as hereinafter defined) with respect to any interest payment date shall be
entitled to receive the interest payable on such interest payment date
notwithstanding the cancellation of such New Mortgage Bonds of the ____ Series
upon any transfer or exchange subsequent to the record date and prior to such
interest payment date; provided, however, that if and to the extent the Company
shall default in the payment of the interest due on such interest payment date,
such defaulted interest shall be paid as provided in Section 3.07 of the
Indenture.

         The term "record date" as used in this Section with respect to any
interest payment date shall mean the _________ or ___________, as the case may
be, next preceding the semi-annual interest payment date, or, if such _________
or _________ shall be a legal holiday or a day on which banking institutions in
the City of Chicago, Illinois, are authorized by law to close, then the next
preceding day which shall not be a legal holiday or a day on which such
institutions are so authorized to close.


                                        2
<PAGE>   3
         SECTION 2. The New Mortgage Bonds of the _____ Series shall be issued
only as registered Bonds without coupons of the denomination of $1,000, or any
integral multiple of $1,000, appropriately numbered. The New Mortgage Bonds of
the ______ Series may be exchanged, upon surrender thereof, at the agency of the
Company in the City of Chicago, Illinois, for one or more new New Mortgage Bonds
of the ____ Series of other authorized denominations, for the same aggregate
principal amount, subject to the terms and conditions set forth in the
Indenture.

         New Mortgage Bonds of the ____ Series may be exchanged or transferred
without expense to the registered owner thereof except that any taxes or other
governmental charges required to be paid with respect to such transfer or
exchange shall be paid by the registered owner requesting such transfer or
exchange as a condition precedent to the exercise of such privilege.

         SECTION 3. The New Mortgage Bonds of the ____ Series and the Trustee's
Certificate of Authentication shall be substantially in the following forms
respectively:


                                        3
<PAGE>   4
                             [FORM OF FACE OF BOND]

                             ILLINOIS POWER COMPANY
             (Incorporated under the laws of the State of Illinois)

                    NEW MORTGAGE BOND, ____% SERIES DUE ____

No.____________                                                 $_______________

         ILLINOIS POWER COMPANY, a corporation organized and existing under the
laws of the State of Illinois (the "Company", which term shall include any
successor corporation as defined in the Indenture hereinafter referred to), for
value received, hereby promises to pay to ________ or registered assigns, the
sum of __________ Dollars ($_________) on the _____ day of ___________, in any
coin or currency of the United States of America which at the time of payment is
legal tender for public and private debts, and to pay interest thereon in like
coin or currency from _____________, payable semi-annually, on the _______ days
of ___________ and _____________ in each year, at the rate of _____________ per
cent (_____%) per annum, until the Company's obligation with respect to the
payment of such principal shall be discharged as provided in the Indenture
hereinafter mentioned. The interest so payable on any ____________ or
___________ will, subject to certain exceptions provided in the Supplemental
Indenture dated as of ____________, _______, be paid to the person in whose name
this Bond is registered at the close of business on the immediately preceding
________ or __________, as the case may be. Both principal of, and interest on,
this Bond are payable at the agency of the Company in the City of Chicago,
Illinois.

         This Bond shall not be entitled to any benefit under the Indenture or
any indenture supplemental thereto, or become valid or obligatory for any
purpose, until the form of certificate endorsed hereon shall have been signed by
or on behalf of Harris Trust and Savings Bank, the Trustee under the Indenture,
or a successor trustee thereto under the Indenture.

         The provisions of this New Mortgage Bond are continued on the reverse
hereof and such continued provisions shall for all purposes have the same effect
as though fully set forth at this place.


                                        4
<PAGE>   5
         IN WITNESS WHEREOF, Illinois Power Company has caused this New Mortgage
Bond to be signed (manually or by facsimile signature) in its name by an
Authorized Executive Officer, as defined in the Indenture, and its corporate
seal (or a facsimile thereof) to be hereto affixed and attested (manually or by
facsimile signature) by an Authorized Executive Officer, as defined in this
Indenture.

Dated ________________, _______             ILLINOIS POWER COMPANY,


                                            By__________________________________
                                                 Authorized Executive Officer

ATTEST:

__________________________________
   Authorized Executive Officer

                [FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION]

         This is one of the Bonds of the series designated therein referred to
in the within-mentioned Indenture dated as of November 1, 1992 and Supplemental
Indenture dated as of ______________, _______.


                                            HARRIS TRUST AND SAVINGS BANK,
                                                                Trustee,


                                            By__________________________________
                                                    Authorized Signatory

                            [FORM OF REVERSE OF BOND]

         This New Mortgage Bond of the _______ Series is one of a duly
authorized issue of Bonds of the Company (the "Bonds") in unlimited aggregate
principal amount, of the series hereinafter specified, all issued and to be
issued under and equally secured by a General Mortgage Indenture and Deed of
Trust (the "Indenture"), dated as of November 1, 1992, executed by the Company
to Harris Trust and Savings Bank (the "Trustee"), as Trustee, to which Indenture
and all indentures supplemental thereto reference is hereby made for a
description of the properties mortgaged and pledged, the nature and extent of
the security, the rights of registered owners of the Bonds and of the Trustee in
respect thereof, and the terms and conditions upon which the Bonds are, and are
to be, secured. The Bonds may be issued in series, for various principal sums,
may mature at different


                                        5
<PAGE>   6
times, may bear interest at different rates and may otherwise vary as provided
in the Indenture. This New Mortgage Bond of the _______ Series is one of a
series designated as the "New Mortgage Bonds, ______% Series Due ________" (the
"New Mortgage Bonds of the ________ Series") of the Company, unlimited in
aggregate principal amount, issued under and secured by the Indenture and
described in the supplemental indenture dated as of ____________, _______ (the
"Supplemental Indenture dated as of __________, _______"), between the Company
and the Trustee, supplemental to the Indenture.

         The New Mortgage Bonds of the ________ Series are not subject to
redemption prior to maturity.

         In case an Event of Default, as defined in the Indenture, shall occur,
the principal of all the New Mortgage Bonds of the ________ Series at any such
time outstanding under the Indenture may be declared or may become due and
payable, upon the conditions and in the manner and with the effect provided in
the Indenture. The Indenture provides that such declaration may be rescinded
under certain circumstances.


                                   ARTICLE II.

                ISSUE OF NEW MORTGAGE BONDS OF THE _____ SERIES.

         SECTION 1. The Company hereby exercises the right to obtain the
authentication of $___________ principal amount of Bonds pursuant to the terms
of Section 4.02 of the Indenture.
All such Bonds shall be New Mortgage Bonds of the _____ Series.

         SECTION 2. Such New Mortgage Bonds of the _____ Series may be
authenticated and delivered prior to the filing for recordation of this
Supplemental Indenture.

                                  ARTICLE III.

                                   REDEMPTION.

         New Mortgage Bonds of the _____ Series [are] [are not] subject to
redemption prior to maturity [as follows].

                                   ARTICLE IV.

                                   THE TRUSTEE

         The Trustee hereby accepts the trusts hereby declared and provided, and
agrees to perform the same upon the terms and conditions in the Indenture set
forth and upon the following terms and conditions:


                                        6
<PAGE>   7
                  The Trustee shall not be responsible in any manner whatsoever
         for or in respect of the validity or sufficiency of this Supplemental
         Indenture or the due execution hereof by the Company or for or in
         respect of the recitals contained herein, all of which recitals are
         made by the Company solely. In general, each and every term and
         condition contained in Article Eleven of the Indenture shall apply to
         this Supplemental Indenture with the same force and effect as if the
         same were herein set forth in full, with such omissions, variations and
         modifications thereof as may be appropriate to make the same conform to
         this Supplemental Indenture.

                                   ARTICLE V.

                            MISCELLANEOUS PROVISIONS.

         This Supplemental Indenture may be simultaneously executed in any
number of counterparts, each of which when so executed shall be deemed to be an
original; but such counterparts shall together constitute but one and the same
instrument.

         IN WITNESS WHEREOF, Illinois Power Company has caused this Indenture to
be executed on its behalf by an Authorized Executive Officer as defined in the
Indenture, and its corporate seal to be hereto affixed and said seal and this
Indenture to be attested by an Authorized Executive Officer as defined in the
Indenture; and said Harris Trust and Savings Bank, in evidence of its acceptance
of the trust hereby created, has caused this Indenture to be executed on its
behalf by its President or one of its Vice Presidents and its corporate seal to
be hereto affixed and said seal and this Indenture to be attested by its
Secretary or one of its Assistant Secretaries; all as of the _____ day of
__________, _______.

                                          ILLINOIS POWER COMPANY


                                          By__________________________________
(CORPORATE SEAL)                                [President/Vice President]

ATTEST:

__________________________________
 [Secretary/Assistant Secretary]


                                          HARRIS TRUST AND SAVINGS BANK, Trustee

                                          By__________________________________
(CORPORATE SEAL)                                [President/Vice President]


                                        7
<PAGE>   8
ATTEST:


__________________________________
 [Secretary/Assistant Secretary]



                                        8
<PAGE>   9
STATE OF ILLINOIS                   )
                                    )  SS.:
COUNTY OF __________                )

         BE IT REMEMBERED, that on this _____ day of ____________, _______,
before me, the undersigned ____________, a Notary Public within and for the
County and State aforesaid, personally came _____________________________ and
_________________________ of Illinois Power Company, a corporation duly
organized, incorporated and existing under the laws of the State of Illinois,
who are personally known to me to be such officers, and who are personally known
to me to be the same persons who executed as such officers the within instrument
of writing, and such persons duly acknowledged that they signed, sealed and
delivered the said instrument as their free and voluntary act as such
_________________ and _____________, respectively, and as the free and voluntary
act of said Illinois Power Company for the uses and purposes therein set forth.

         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.

                              __________________________________________________
                                   Notary Public, ________ County, Illinois

My Commission Expires _______________.

(NOTARIAL SEAL)




STATE OF ILLINOIS                   )
                                    )
COUNTY OF ______                    ) SS.:

         BE IT REMEMBERED, that on this ____ day of _________, ______, before
me, the undersigned ________________, a Notary Public within and for the County
and State aforesaid, personally came _________________________ and
___________________________, of Harris Trust and Savings Bank, a corporation
duly organized, incorporated and existing under the laws of the State of
Illinois, who are personally known to me to be the same persons who executed as
such officers the within instrument of writing, and such persons duly
acknowledged that they signed, sealed and delivered the said instrument as their
free and voluntary act as such ______________ and ________________,
respectively, and as the free and voluntary act of said Harris Trust and Savings
Bank for the uses and purposes therein set forth.


                                        9
<PAGE>   10
         IN WITNESS WHEREOF, I have hereunto subscribed my name and affixed my
official seal on the day and year last above written.

                              __________________________________________________
                                   Notary Public, __________ County, Illinois

My Commission Expires ____________.

(NOTARIAL SEAL)



Return To:                                This Instrument Was Prepared By:
         ILLINOIS POWER COMPANY                   Schiff Hardin & Waite
         Attention: ________________              7200 Sears Tower
         500 S. 27th Street                       Chicago, IL 60606
         Decatur, IL 62525




                                       10

<PAGE>   1
                                                                    EXHIBIT 4.50

                                                                     (Note Form)

                           [Form of Face of Security]
No.___________                                                   $______________


                             ILLINOIS POWER COMPANY
             (Incorporated Under the Laws of the State of Illinois)

                                 _____% Note Due _____

         Illinois Power Company, a corporation organized and existing under the
laws of the State of Illinois (hereinafter called the "Company," which term
shall include any successor corporation as defined in the Indenture hereinafter
referred to) for value received hereby promises to pay to
_______________________ or registered assigns, the principal sum of
_______________________ Dollars ($___________) on __________________.


                  Interest Payment Dates:_____________________
                      Record Dates:_______________________

         See the reverse side hereof for additional provisions, including
certain definitions.

         In Witness Whereof, Illinois Power Company has caused this Note to be
signed (manually or by facsimile signature) in its name by its President or any
Vice President, and its corporate seal (or a facsimile thereof) to be hereto
affixed and attested (manually or by facsimile signature) by its Secretary or an
Assistant Secretary.

Dated: ______________, _____

Authenticated: ______________, _____


THE CHASE MANHATTAN BANK                                ILLINOIS POWER COMPANY
         as Trustee

By _______________________________                  By _________________________
         Authorized Officer                             Its ____________________

                  or                                             (SEAL)


___________________________________                 By _________________________
         as Authenticating Agent                        Its


By ________________________________
         Authorized Officer
<PAGE>   2
                          [Form of Reverse of Security]

                             ILLINOIS POWER COMPANY
                                ______% Note Due _____

         1. Interest. Illinois Power Company, an Illinois corporation (the
         "Company"), promises to pay interest on the principal amount of this
         Security at the rate per annum shown above. The Company will pay
         interest semiannually on _______________ and _______________ of each 
         year. Interest on the Securities (as hereinafter defined) will accrue
         from the most recent date to which interest has been paid or, if no
         interest has been paid or duly provided for, from ________________.

         2. Method of Payment. The Company will pay interest on the Securities
         (except defaulted interest) to the persons who are registered holders
         of Securities at the close of business on the ___________ or
         ____________ next preceding the interest payment date even though
         Securities are cancelled after the record date and on or before the
         interest payment date. Holders must surrender Securities to a Paying
         Agent at a Place of Payment to collect principal payments. The Company
         will pay principal (and premium, if any) and interest in money of the
         United States that at the time of payment is legal tender for payment
         of public and private debts. However, the Company may pay principal
         (and premium, if any) and interest by its check payable in such money.
         The Company may mail an interest check to a holder's registered
         address.

         3. Paying Agent, Registrar, Place of Payment. The Company maintains an
         office or agency in the Borough of Manhattan, in the City of New York,
         New York where the Securities may be presented or surrendered for
         payment, registration of transfer or exchange and where notices and
         demands with respect to the Securities may be made. Initially, The
         Chase Manhattan Bank (the "Trustee"), ______________________, New York,
         New York _______, will act as Paying Agent and Registrar and the Place
         of Payment is the office of the Trustee set forth above, Attention:
         __________________. The Company may appoint Co-Paying Agents or
         Co-Registrars and change any Paying Agent, Registrar, Place of Payment
         or Co-Paying Agent or Co-Registrar without notice. The Company may act
         as Paying Agent, Registrar or Co-Registrar.

         4. Indenture. This Security is one of a duly authorized issue of
         debentures, notes or other evidences of indebtedness of the Company
         (hereinafter called the "Debt Securities") of the series hereinafter
         specified, all issued or to be issued under and pursuant to an
         indenture dated as of July 15, 1986 (hereinafter called the
         "Indenture"), between the Company and the Trustee to which Indenture
         and all indentures supplemental thereto (including those provisions of
         the Trust Indenture Act of 1939 made a part thereof) reference is
         hereby made for a description of the rights, limitations of rights,
         obligations, duties and immunities thereunder of the Trustee, the
         Company and the holders of the Debt Securities. The Debt Securities may
         be issued in one or more series, which different series may be issued
         in various aggregate principal amounts, may mature at different times,
         may bear interest (if any) at different rates, may be subject to
         different redemption provisions (if any), may be subject to different
         sinking, purchase or analogous funds (if any), may be subject to
         different covenants and Events of Default and may otherwise vary as in
         the Indenture provided. This Security is one of a series designated as
         the ___________ Notes Due _________ of the Company (herein called the
         "Securities"), limited in aggregate principal amount to $__________
         (except for Securities issued in substitution for destroyed, lost or
         stolen Securities).

                                        2
<PAGE>   3
         The Securities are unsecured general obligations of the Company.

         5. Denominations, Transfer, Exchange. The Securities are in registered
         form without coupons in denominations of $__________ and whole
         multiples of $___________ . The transfer of Securities may be
         registered and Securities may be exchanged as provided in the
         Indenture. The Registrar may require a holder, among other things, to
         furnish appropriate endorsements and transfer documents and to pay any
         taxes and fees required by law or permitted by the Indenture. [The
         Registrar need not exchange or register the transfer of any Security or
         portion of a Security selected for redemption. Also, it need not
         exchange or register the transfer of any Securities for a period of 15
         days before a selection of Securities to be redeemed. ]

         6. Persons Deemed Owners. The registered holder of a Security may be
         treated as its owner for all purposes.

         7. Amendments and Waivers. Subject to certain exceptions, the Indenture
         may be amended with the consent of the holders of at least a majority
         in aggregate principal amount of the Securities together with the
         consent of the holders of at least a majority in aggregate principal
         amount of each other series of Debt Securities which are affected by
         the amendment. Subject to certain exceptions, the Securities may be
         amended with the consent of the holders of at least a majority in
         aggregate principal amount of the Securities and any existing default
         may be waived with the consent of the holders of a majority in
         aggregate principal amount of the Securities. Without the consent of
         any Securityholder, the Indenture or the Securities may be amended to
         cure any ambiguity, defect or inconsistency, to provide for assumption
         of Company obligations to Securityholders or to make any change that
         does not adversely affect the rights of any Securityholder.

         8. Defaults and Remedies. An Event of Default is: (a) default for 30
         days in payment of interest on the Securities; (b) default for 3
         Business Days in payment of principal (and premium, if any) on these
         Securities; (c) failure by the Company for 60 days after notice to it
         to comply with any of its other agreements in the Indenture or the
         Securities; and (d) certain events of bankruptcy or insolvency. If an
         Event of Default occurs and is continuing, the Trustee or the holders
         of at least 33% in aggregate principal amount of the Securities may
         declare all the Securities to be due and payable immediately.
         Securityholders may not enforce the Indenture or the Securities except
         as provided in the Indenture. The Trustee may require indemnity
         satisfactory to it before tit enforces the Indenture or the Securities.
         Subject to certain limitations, holders of a majority in aggregate
         principal amount of the Securities may direct the Trustee in its
         exercise of any trust or power. The Trustee may withhold from
         Securityholders notice of any continuing default (except a default in
         payment of principal (and premium, if any) or interest) if it
         determines that withholding notice is in their interests. The Company
         must furnish an annual compliance statement to the Trustee.

         9. Trustee Dealings with Company. The Chase Manhattan Bank, the Trustee
         under the Indenture, in its individual or any other capacity, may make
         loans to, accept deposits from, and perform services for the Company or
         its affiliates, and may otherwise deal with the Company or its
         affiliates, as if it were not Trustee.

         10. No Recourse Against Others. A director, officer, employee or
         stockholder, as such, of the Company shall not have any liability for
         any obligations of the Company under the Securities or

                                        3
<PAGE>   4
         the Indenture or for any claim based on, in respect of or by reason of
         such obligations or their creation. Each Securityholder by accepting a
         Security waives and releases all such liability. The waiver and release
         are part of the consideration for the issue of the Securities.

         11. Authentication. This Security shall not be valid or obligatory for
         any purpose or be entitled to any benefit under the Indenture unless
         the Certificate of Authorization hereon has been executed by the
         Trustee or an authenticating agent by the manual signature of the
         Trustee or an authenticating agent.

         12. Abbreviations. Customary abbreviations may be used in the name of a
         Securityholder or an assignee, such as: TEN COM (=tenants in common),
         TEN ENT (=tenants by the entireties), JT TEN (=joint tenants with right
         of survivorship and not as tenants in common), CUST (=Custodian), and
         U/G/M/A (=Uniform Gifts to Minors Act).

         The Company will furnish to any Securityholder upon written request and
without charge a copy of the Indenture. Requests may be made to: Illinois Power
Company, Attention: Secretary, 500 South 27th Street, Decatur, Illinois 62525.




                                        4

<PAGE>   1
                                                                    EXHIBIT 4.51

                                                                 (Debenture with
                                                              Sinking Fund Form)

                           [Form of Face of Security]

No._____________                                                   $____________


                             ILLINOIS POWER COMPANY
             (Incorporated Under the Laws of the State of Illinois)
                        _____% Debenture Due ___________

         Illinois Power Company, a corporation organized and existing under the
laws of the State of Illinois (hereinafter called the "Company", which term
shall include any successor corporation as defined in the Indenture hereinafter
referred to) for value received, hereby promises to pay to ________or registered
assigns, the principal sum of __________ Dollars ($___________) on ___________.

                 Interest Payment Dates: ______________________
                        Record Dates:___________________

         See the reverse side hereof for additional provisions, including
certain definitions.

         In Witness Whereof, Illinois Power Company has caused this Security to
be signed (manually or by facsimile signature) in its name by its President or
any Vice President, and corporate seal (or a facsimile thereof) to be hereto
affixed and attested (manually or by facsimile signature) by its Secretary or an
Assistant Secretary.

Dated: ______________, _____

Authenticated: ______________, _____


THE CHASE MANHATTAN BANK                                ILLINOIS POWER COMPANY
         as Trustee

By _______________________________                  By _________________________
         Authorized Officer                             Its ____________________

                  or                                             (SEAL)


___________________________________                 By _________________________
         as Authenticating Agent                        Its


By ________________________________
         Authorized Officer
<PAGE>   2
                         [Form of Reverse of Security]

                             ILLINOIS POWER COMPANY
                       ______% Debenture Due ____________

                  1. Interest. Illinois Power Company, an Illinois corporation
         (the "Company"), promises to pay interest on the principal amount of
         this Security at the rate per annum shown above. The Company will pay
         interest semiannually on ____________ and _________ of each year.
         Interest on the Securities (as hereinafter defined) will accrue from
         the most recent (date to which interest has been paid or, if no
         interest has been paid, from ________________.


                  2. Method of Payment. The Company will pay interest on the
         Securities (except defaulted interest) to the persons who are
         registered holders of Securities at the close of business on the
         _____________ or _______________ next preceding the interest payment
         date even though Securities are cancelled after the record date and on
         or before the interest payment date. Holders must surrender Securities
         to a Paying Agent at a Place of Payment to collect principal payments.
         The Company will pay principal (and premium, if any) and interest in
         money of the United States that at the time of payment is legal tender
         for payment of public and private debts. However, the Company may pay
         principal (and premium, if any) and interest by its check payable in
         such to collect principal payments. The Company will pay principal (and
         premium. if any) and interest in money of the United States that at the
         time of payment is legal tender for payment of public and private
         debts. However. the Company may pay principal (and premium; if any) and
         interest by its check payable in such money. The Company may mail an
         interest check to a holder's registered address.

                  3. Paying Agent, Registrar, Place of Payment. The Company
         maintains an office or agency in the Borough of Manhattan in the City
         of New York, New York where the Securities may be presented or
         surrendered for payment, registration of transfer or exchange and where
         notices and demands with respect to the Securities may be made.
         Initially, The Chase Manhattan Bank (the "Trustee"), _______________,
         New York, New York ______, will act as Paying Agent and Registrar and
         the Place of Payment is the office of the Trustee set forth above,
         Attention: ________________. The Company may appoint Co-Paying Agents
         or Co-Registrars and change any Paying Agent, Registrar, Place of
         Payment or Co-Paying Agent or Co-Registrar without notice. The Company
         may act as Paying Agent, Registrar or Co-Registrar.

                  4. Indenture. This Security is one of a duly authorized issue
         of debentures, notes or other evidences of indebtedness of the Company
         (hereinafter called the "Debt Securities") of the series hereinafter
         specified, all issued or to be issued under and pursuant to an
         indenture dated as of July 15, 1986 (herein called the "Indenture"),
         between the Company and the Trustee to which Indenture and all
         indentures supplemental thereto (including those provisions of the
         Trust Indenture Act of 1939 made a part thereof) reference is hereby
         made for a description of the rights, limitations of rights,
         obligations, duties and immunities thereunder of the Trustee, the
         Company and the holders of the Debt Securities. The Debt Securities may
         be issued in one or more series, which different series may be issued
         in various aggregate principal amounts, may mature at different times,
         may bear interest (if any) at different rates, may be subject to
         different redemption

                                        2
<PAGE>   3
         provisions (if any), may be subject to different sinking, purchase or
         analogous funds (if any), may be subject to different covenants and
         Events of Default and may otherwise vary as in the Indenture provided.
         This Security is one of a series designated as the _____% Debentures
         Due ______________ of the Company (herein called the "Securities"),
         limited in aggregate principal amount to $___________ (except for
         Securities issued in substitution for destroyed, lost or stolen
         Securities). The Securities are unsecured general obligations of the
         Company.

                  5. [Optional Redemption. The Company may redeem all the
         Securities at any time or some of them from time to time at the
         following redemption prices (expressed in percentages of principal
         amount), plus accrued interest to the redemption date:

                  YEAR           PERCENTAGE      YEAR        PERCENTAGE
                  _______        _________       _______     __________
                  _______        _________       _______     __________
                  _______        _________       _______     __________
                  _______        _________       _______     __________
                  _______        _________       _______     __________

         However, the Company may not so redeem Securities before ____________
         directly or indirectly from or in anticipation of money borrowed by or
         for the account of the Company or a subsidiary at an interest cost of
         less than ______% per annum.]

                  6. [Mandatory Redemption. (a) The Company will redeem $_______
         principal amount of Securities on ___________ and on each _______
         thereafter through _________ at a redemption price of 100% of principal
         amount, plus accrued interest to the redemption date. As and for a
         sinking fund for the retirement of such Securities, the Company will,
         until all the Securities are paid or payment thereof provided for,
         deposit with the Trustee, prior to _______ in each of the years _______
         to _________, inclusive an amount in cash sufficient to pay the
         redemption price of the Securities to be redeemed in such year as
         provided above in this subparagraph (a), less the amount of any credit
         against such payment received by the Company under the following
         subparagraph. Each such sinking fund payment shall be applied to the
         redemption of Securities on such __________ as herein provided.

                  (b) The Company may deliver Securities theretofore acquired by
         the Company or apply Securities previously redeemed (other than any
         Securities previously redeemed through the operation of the sinking
         fund) in satisfaction of all or any part of any sinking fund payment
         required to be made pursuant to the preceding subparagraph; provided
         that such Securities shall not have been theretofore used for the
         purpose of any such credit. Each such Security shall be credited for
         such purpose by the Trustee at the redemption price set forth in the
         preceding subparagraph for redemption through the operation of the
         sinking fund and the amount of such sinking fund payment shall be
         reduced accordingly.

                  (c) If in any year commencing with the year __________ to and
         including the year ____________ the Company shall elect to satisfy all
         or any part of the next ensuing sinking fund payment by crediting
         Securities pursuant to the preceding subparagraph, then on or before
         _______________ in such year the Company will deliver to the Trustee an
         Officers' Certificate specifying the portions of the next ensuing
         sinking fund payment which are to be satisfied,

                                        3
<PAGE>   4
         respectively, by payment of cash, by delivering Securities theretofore
         acquired and by application of previously redeemed Securities, and will
         deliver to the Trustee any Securities to be so delivered. In case of
         the failure, on or before __________ in any such year, of the Company
         to give such notice and to deliver any such Securities, the next
         ensuing sinking fund obligation shall be paid entirely in cash. On or
         before ______________ in each such year the Trustee shall select the
         Securities to be redeemed upon the next ensuing ________________ in the
         manner specified in the Indenture, and shall cause notice of the
         redemption thereof to be given in the name of and at the expense of the
         Company in the manner provided in the Indenture. Such notice having
         been duly given, the redemption of such Securities shall be made on
         such _____________ upon the terms and in the manner set forth herein. ]

                  7. [Additional Optional Redemption. In addition to redemptions
         pursuant to paragraph ________, the company may redeem not more than
         $__________ principal amount of Securities on _________ and on each
         __________ thereafter through _____________ at a redemption price of
         100% of aggregate principal amount, plus accrued interest to the
         redemption date.]

                  8. Notice of Redemption. Notice of redemption will be mailed
         at least 30 days but not more than 60 days before the redemption date
         to each holder of Securities to be redeemed at his registered address.
         Securities in denominations larger than $_____________ may be redeemed
         in part but only in whole multiples of $________________. On and after
         the redemption date interest ceases to accrue on Securities or portions
         of them called for redemption.

                  9. Denominations, Transfer, Exchange. The Securities are in
         registered form without coupons in denominations of $____________ and
         whole multiples of $____________. The transfer of Securities may be
         registered and Securities may be exchanged as provided in the
         Indenture. The Registrar may require a holder, among other things, to
         furnish appropriate endorsements and transfer documents and to pay any
         taxes and fees required by law or permitted by the Indenture. The
         Registrar need not exchange or register the transfer of any Security or
         portion of a Security selected for redemption. Also, it need not
         exchange or register the transfer of any Securities for a period of 15
         days before a selection of Securities to be redeemed.

                  10. Persons Deemed Owners. The registered holder of a Security
         may be treated as its owner for all purposes.

                  11. Amendments and Waivers. Subject to certain exceptions, the
         Indenture may be amended with the consent of the holders of at least a
         majority in aggregate principal amount of the Securities together with
         the consent of the holders of at least a majority in aggregate
         principal amount of each other series of Debt Securities which are
         affected by the amendment. Subject to certain exceptions, the
         Securities may be amended with the consent of the holders of at least a
         majority in aggregate principal amount of the Securities and any
         existing default may be waived with the consent of the holders of a
         majority in aggregate principal amount of the Securities. Without the
         consent of any Securityholder, the Indenture or the Securities may be
         amended to cure any ambiguity, defect or inconsistency, to provide for
         assumption of Company obligations to Securityholders or to make any
         change that does not adversely affect the rights of any Securityholder.


                                        4
<PAGE>   5
                  12. Defaults and Remedies. An Event of Default is: (a) default
         for 30 days in payment of interest on the Securities; (b) default for 3
         Business Days in payment of principal (and premium, if any) on them;
         (c) failure by the Company for 60 days alter notice to it to comply
         with any of its other agreements in the Indenture or the Securities;
         and (d) certain events of bankruptcy or insolvency. If an Event of
         Default occurs and is continuing, the Trustee or the holders of at
         least 33% in aggregate principal amount of Securities may declare all
         the Securities to be due and payable immediately. Securityholders may
         not enforce the Indenture or the Securities except as provided in the
         Indenture. The Trustee may require indemnity satisfactory to it before
         it enforces the Indenture or the Securities. Subject to certain
         limitations, holders of a majority in aggregate principal amount of the
         Securities may direct the Trustee in its exercise of any trust or
         power. The Trustee may withhold from Securityholders notice of any
         continuing default (except a default in payment of principal (and
         premium, if any) or interest) if it determines that withholding notice
         is in their interests. The Company must furnish an annual compliance
         statement to the Trustee.

                  13. Trustee Dealings with Company. The Chase Manhattan Bank,
         the Trustee under the Indenture, in its individual or any other
         capacity, may make loans to, accept deposits from, and perform services
         for the Company or its affiliates, and may otherwise deal with the
         Company or its affiliates, as if it were not Trustee.

                  14. No Recourse Against Others. A director, officer, employee
         or stockholder, as such, of the Company shall not have any liability
         for any obligations of the Company under the Securities or the
         Indenture or for any claim made on, in respect of or by reason of such
         obligations or their creation. Each Securityholder by accepting a
         Security waives and releases all such liability. The waiver and release
         are part of the consideration for the issue of the Securities.

                  15. Authentication. This Security shall not be valid until
         authenticated by the manual signature of the Trustee or an
         authenticating agent.

                  16. Abbreviations. Customary abbreviations may be used in the
         name of a Securityholder or an assignee, such as: TEN COM (= tenants
         in common), TEN ENT (= tenants by the entireties), JT TEN (= joint
         tenants with right of survivorship and not as tenants in common), CUST
         (= Custodian), and U/G/M/A(= Uniform Gifts to Minors Act).

         The Company will furnish to any Securityholder upon written request and
without charge a copy of the Indenture. Requests may be made to: Illinois Power
Company, Attention: Secretary, 500 South 27th Street, Decatur, Illinois 62525.



                                        5

<PAGE>   1
Illinois Power Company
January 22, 1999
Page 2

                                                                       EXHIBIT 5

                       [Schiff Hardin & Waite Letterhead]


Robert J. Regan
(312) 258-5606


                                January 22, 1999



Illinois Power Company
500 S. 27th Street
Decatur, Illinois 62525-1805

              RE: $250,000,000 PRINCIPAL AMOUNT OF DEBT SECURITIES

Ladies and Gentlemen:

                  We are acting as counsel for Illinois Power Company (the
"Company") in connection with the registration of an aggregate of $250,000,000
principal amount of debt securities, including the Company's New Mortgage Bonds
(the "New Mortgage Bonds") or other debt securities (the "New Unsecured Debt")
in one or more series. Each series of New Mortgage Bonds would be issued
pursuant to the General Mortgage Indenture and Deed of Trust dated as of
November 1, 1992 between the Company and Harris Trust and Savings Bank, as
Trustee, and a supplemental indenture (the "New Mortgage Supplemental
Indenture"), providing for the issuance of such series (the General Mortgage
Indenture and Deed of Trust and all indentures supplemental thereto are
collectively called the "New Mortgage"). Each series of New Unsecured Debt would
be issued pursuant to the Indenture dated as of July 15, 1986 between the
Company and The Chase Manhattan Bank, as Trustee, and a supplemental indenture
(the "Unsecured Supplemental Indenture"), or a resolution duly adopted by the
Board of Directors of the Company, providing for the issuance of such series.

                  As counsel for the Company, we have examined such corporate
records of the Company and have made such inquiry and further investigation as
we deemed necessary in order to enable us to render this opinion. We have
assumed the continued exemption of the contemplated transactions from the
requirements of the Public Utility Holding Company Act of 1935, as amended to
date, the genuineness of all signatures, the authenticity of all documents
submitted to us as original counterparts, and the conformity to the originals of
all documents submitted to us as certified or photostatic copies.

                  Based upon the foregoing, we are of the opinion that:

                  1. The Company is a corporation validly organized and existing
under and by virtue of the laws of the State of Illinois.

                  2. If the debt securities are New Mortgage Bonds, when the
Registration Statement on Form S-3 relating to the New Mortgage Bonds and New
Unsecured Debt (the "Registration Statement") has become effective and providing
no stop order shall have been issued by the Securities and Exchange Commission
relating thereto, and when the Illinois Commerce Commission shall have entered
an order
<PAGE>   2
Illinois Power Company
January 22, 1999
Page 2

authorizing the execution and delivery of a New Mortgage Supplemental Indenture
or New Mortgage Supplemental Indentures and the issuance and sale of one or more
series of New Mortgage Bonds, and said order shall remain in effect, then upon
the execution and delivery of the New Mortgage Supplemental Indenture or New
Mortgage Supplemental Indentures and the issuance and sale of one or more series
of the New Mortgage Bonds pursuant to the due authorization by the Board of
Directors of the Company, such New Mortgage Bonds will be the legal and binding
obligations of the Company, enforceable in accordance with their terms, subject
to the due filing of the New Mortgage Supplemental Indenture or New Mortgage
Supplemental Indentures relating thereto for record in the manner prescribed
with respect to real estate mortgages and the issuance and sale of the New
Mortgage Bonds thereunder before the intervention of any lien to which the New
Mortgage is not expressly made subject, or not expressly excepted by the New
Mortgage, and subject to the reservations, encumbrances and restrictions recited
in the granting clause of, and as provided in, the New Mortgage or referred to
in the Prospectus included in the Registration Statement under the subcaption
"Security" under the caption "Description of the New Mortgage Bonds," and except
as the legality, binding effect or enforceability of the New Mortgage Bonds may
be limited or otherwise affected by (a) bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium or similar laws affecting creditors'
rights generally, or (b) the application of general principles of equity
(regardless of whether the application of such principles is considered in a
proceeding in equity or at law).

                  3. If the debt securities are New Unsecured Debt, when the
Registration Statement has become effective and providing no stop order shall
have been issued by the Securities and Exchange Commission relating thereto, and
when the Illinois Commerce Commission shall have entered an order authorizing
the issuance and sale of New Unsecured Debt, and said order shall remain in
effect, then upon the execution and delivery of the Unsecured Supplemental
Indenture or Unsecured Supplemental Indentures (if applicable) and the issuance
and sale of one or more series of the New Unsecured Debt pursuant to the due
authorization by the Board of Directors of the Company, such New Unsecured Debt
will be the legal and binding obligation of the Company enforceable in
accordance with its terms, except as the legality, binding effect or
enforceability of the New Unsecured Debt may be limited or otherwise affected by
(a) bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium,
or similar laws affecting creditors' rights generally, or (b) the application of
general principles of equity (regardless of whether the application of such
principles is considered in a proceeding in equity or at law).

                  We hereby consent to the use of this opinion as an exhibit to
the Registration Statement to be filed with the Securities and Exchange
Commission under the Securities Act of 1933 and the reference to us under the
caption "Legal Opinions" in the Prospectus contained in the Registration
Statement.

                                            Very truly yours,

                                            SCHIFF HARDIN & WAITE



                                            By: /s/ Robert J. Regan 
                                               -------------------------------
RJR:                                                Robert J. Regan


<PAGE>   1
                                                                      EXHIBIT 12


                             ILLINOIS POWER COMPANY
                STATEMENT OF COMPUTATION OF RATIO OF EARNINGS TO
                                 FIXED CHARGES
                             (Thousands of Dollars)


<TABLE>
<CAPTION>
                                                                                  Year Ended December 31,        
                                              -------------------------------------------------------------------------------------
                                                1993         1993**        1994        1995       1996          1997       1997***
                                              ----------   ---------    ---------   ---------   ---------    ---------    ---------
<S>                                           <C>          <C>          <C>         <C>         <C>          <C>          <C>      
Earnings Available for Fixed Charges:         
Net Income (Loss)                             $ (56,038)   $ (56,038)   $ 180,242   $ 182,713   $ 228,618    $ (44,173)   $ (44,173)
 Add:
  Income Taxes:
   Current                                       25,260       25,260       58,354      98,578     163,873       72,680       76,680
   Deferred - Net                                82,057       82,057       71,177      34,137     (16,028       36,963       36,963
  Allocated income taxes                        (12,599)     (12,599)      (8,285)     (8,417)     (2,642)      (1,446)      (1,446)
  Investment tax credit - deferred                 (782)        (782)     (11,331)     (6,894)     (7,278)      (7,278)      (7,278)
  Income tax effect of disallowed 
    costs                                       (70,638)     (70,638)        --          --          --           --           --   
  Income tax effect of FAS 71 write-off            --           --           --          --          --       (117,998)    (117,998)
  Interest on long-term debt                    154,110      154,110      135,115     125,581     118,438      109,595      109,595
  Amortization of debt expense and
   premium-net, and other interest 
   charges                                       17,007       17,007       15,826      29,558      22,325       26,260       26,260
  One-third of all rentals (Estimated 
   to be representative of the 
   interest components)                           5,992        5,992        5,847       5,221       4,346        4,229        4,229
  Interest on in-core fuel                        6,174        6,174        7,185       6,716       4,757        3,842        3,842
  Disallowed Clinton plant costs                   --        270,956         --          --          --           --           --   
  FAS 71 Regulatory Write-Offs                     --           --           --          --          --           --        313,030
                                              ---------    ---------    ---------   ---------   ---------    ---------    ---------
Earnings (loss) available for fixed charges   $ 150,543    $ 421,499    $ 454,130   $ 467,193   $ 516,409    $  82,674    $ 395,704
                                              =========    =========    =========   =========   =========    =========    =========

Fixed charges:
 Interest on long-term debt                     154,110    $ 154,110    $ 135,115   $ 125,581   $ 118,438    $ 109,595    $ 109,595
 Amortization of debt expense and
  premium-net, and other interest 
  charges                                        27,619       27,619       25,381      38,147      28,957       31,204       31,204
 One-third of all rentals (Estimated 
  to be representative of the interest        
  component)                                      5,992        5,992        5,847       5,221       4,346        4,229        4,229
                                              ---------    ---------    ---------   ---------   ---------    ---------    ---------
Total Fixed Charges                           $ 187,721    $ 187,721    $ 166,343   $ 168,949   $ 151,741    $ 145,028    $ 145,028
                                              =========    =========    =========   =========   =========    =========    =========

Ratio of earnings to fixed charges                 0.80*        2.25         2.73        2.77        3.40         0.57*        2.73
                                              =========    =========    =========   =========   =========    =========    =========

<CAPTION>

                                                               Twelve                
                                                             Months Ended            
                                                               September             
                                                         -------------------------   
                                                           1998          1998***     
                                                         -------------------------   
<S>                                                      <C>           <C>           
Earnings Available for Fixed Charges:                                                
Net Income (Loss)                                        $(197,357)    $(197,357)    
 Add:                                                                                
  Income Taxes:                                                                      
   Current                                                  25,854        25,854     
   Deferred - Net                                          (34,073)      (34,073)    
  Allocated income taxes                                    (2,118)       (2,118)    
  Investment tax credit ( deferred                          (7,278)       (7,278)    
  Income tax effect of disallowed costs                       --            --       
  Income tax effect of FAS 71 write-off                   (117,998)     (117,998)              
  Interest on long-term debt                               104,971       104,971     
  Amortization of debt expense and                                                   
   premium-net, and other interest charges                  29,632        29,632     
  One-third of all rentals (Estimated to be                                          
   representative of the interest components)                4,090         4,090     
  Interest on in-core fuel                                   3,816         3,816     
  Disallowed Clinton plant costs                              --            --       
  FAS 71 Regulatory Write-Offs                                --         313,030     
                                                         --------      ---------     
Earnings (loss) available for fixed charges              $(190,461)    $ 122,569     
                                                         =========     =========     
                                                                                     
Fixed charges:                                                                       
 Interest on long-term debt                              $ 104,971     $ 104,971     
 Amortization of debt expense and                                                    
  premium-net, and other interest charges                   37,326        37,326     
 One-third of all rentals (Estimated to be                                           
  representative of the interest                                                     
  component)                                                 4,090         4,090     
                                                         ---------     ---------     
Total Fixed Charges                                      $ 146,387     $ 146,387     
                                                         =========     =========     
                                                                                     
Ratio of earnings to fixed charges                           (1.30)*        0.84     
                                                         =========     =========     
</TABLE>



*    Earnings are inadequate to cover fixed charges. Additional earnings
     (thousands) for 1993, 1997 and Twelve Months Ended September 30, 1998
     of $37,178, $62,354, and $336,848.
                                                                               
**   Supplemental ratio of earnings to fixed charges presented to exclude
     nonrecurring item - Disallowed Clinton plant costs.
                                                                               
***  Supplemental ratio of earnings to fixed charges presented to exclude
     write-off related to the discontinued application of SFAS 71, "Accounting
     for the Effects of Certain Types of Regulation" for the generation segment
     of the business.

<PAGE>   1
                                                                    EXHIBIT 23.1




                       CONSENT OF INDEPENDENT ACCOUNTANTS


We hereby consent to the incorporation by reference in the Prospectus
constituting part of this Registration Statement on Form S-3 of our report dated
February 12, 1998, which appears on page a-10 of the 1997 Annual Report to
Shareholders of Illinois Power Company, which is incorporated by reference in
Illinois Power Company's Annual Report on Form 10-K for the year ended December
31, 1997. We also consent to the incorporation by reference of our report on the
Financial Statement Schedules, which appears on page 27 of such Annual Report on
Form 10-K. We also consent to the reference to us under the heading "Experts" in
such Prospectus.



  /s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP
St. Louis, Missouri
January 22, 1999

<PAGE>   1
                                                                    EXHIBIT 26.1


                     SECURITIES AND EXCHANGE COMMISSION
                           Washington, D.C.  20549


                                  FORM T-1

                          Statement of Eligibility
                    Under the Trust Indenture Act of 1939
                of a Corporation Designated to Act as Trustee

              Check if an Application to Determine Eligibility
              of a Trustee Pursuant to Section 305(b)(2) ______



                        HARRIS TRUST AND SAVINGS BANK
                              (Name of Trustee)

                                      

        Illinois                                         36-1194448
(State of Incorporation)                    (I.R.S. Employer Identification No.)

              111 West Monroe Street, Chicago, Illinois  60603
                  (Address of principal executive offices)


              Judith Bartolini, Harris Trust and Savings Bank,
              311 West Monroe Street, Chicago, Illinois, 60606
                 312-461-2527 phone   312-461-3525 facsimile
         (Name, address and telephone number for agent for service)






                           ILLINOIS POWER COMPANY
                                  (Obligor)

                                      

        Illinois                                          37-0344645
(State of Incorporation)                    (I.R.S. Employer Identification No.)


                            500 South 27th Street
                           Decatur Illinois 62525
                  (Address of principal executive offices)



                             New Mortgage Bonds
                       (Title of indenture securities)



<PAGE>   2


1.   GENERAL INFORMATION.  Furnish the following information as to the Trustee:

     (a)  Name and address of each examining or supervising authority to which
          it is subject.

          Commissioner of Banks and Trust Companies, State of Illinois,
          Springfield, Illinois; Chicago Clearing House Association, 164 West
          Jackson Boulevard, Chicago, Illinois; Federal Deposit Insurance
          Corporation, Washington, D.C.; The Board of Governors of the Federal
          Reserve System, Washington, D.C.

     (b)  Whether it is authorized to exercise corporate trust powers.

          Harris Trust and Savings Bank is authorized to exercise corporate
          trust powers.

2.   AFFILIATIONS WITH OBLIGOR.  If the Obligor is an affiliate of the Trustee, 
     describe each such affiliation.

          The Obligor is not an affiliate of the Trustee.

3. through 15.

          NO RESPONSE NECESSARY

16.  LIST OF EXHIBITS.

     1. A copy of the articles of association of the Trustee as now in effect 
        which includes the authority of the trustee to commence business and to
        exercise corporate trust powers.

        A copy of the Certificate of Merger dated April 1, 1972 between Harris
        Trust and Savings Bank, HTS Bank and Harris Bankcorp, Inc. which
        constitutes the articles of association of the Trustee as now in effect
        and includes the authority of the Trustee to commence business and to
        exercise corporate trust powers was filed in connection with the
        Registration Statement of Louisville Gas and Electric Company, File No.
        2-44295, and is incorporated herein by reference.

     2. A copy of the existing by-laws of the Trustee.

        A copy of the existing by-laws of the Trustee was filed in connection
        with the Registration Statement of Commercial Federal Corporation, File
        No. 333-20711, and is incorporated herein by reference.

     3. The consents of the Trustee required by Section 321(b) of the Act.

          (included as Exhibit A on page 2 of this statement)

     4. A copy of the latest report of condition of the Trustee published 
        pursuant to law or the requirements of its supervising or examining 
        authority.

          (included as Exhibit B on page 3 of this statement)


                                      1


<PAGE>   3


                                  SIGNATURE

                                      
Pursuant to the requirements of the Trust Indenture Act of 1939, the Trustee,
HARRIS TRUST AND SAVINGS BANK, a corporation organized and existing under the
laws of the State of Illinois, has duly caused this statement of eligibility to
be signed on its behalf by the undersigned, thereunto duly authorized, all in
the City of Chicago, and State of Illinois, on the 12th day of January, 1999.

HARRIS TRUST AND SAVINGS BANK


By:  /s/ J. Bartolini
   -----------------------
     J. Bartolini
     Vice President

EXHIBIT A

The consents of the trustee required by Section 321(b) of the Act.

Harris Trust and Savings Bank, as the Trustee herein named, hereby consents
that reports of examinations of said trustee by Federal and State authorities
may be furnished by such authorities to the Securities and Exchange Commission
upon request therefor.

HARRIS TRUST AND SAVINGS BANK


By:  /s/ J. Bartolini
   -----------------------
     J. Bartolini
     Vice President


                                      2


<PAGE>   4
                                      


EXHIBIT B
Attached is a true and correct copy of the statement of condition of Harris
Trust and Savings Bank as of September 30, 1998, as published in accordance
with a call made by the State Banking Authority and by the Federal Reserve
Bank of the Seventh Reserve District.

                            [LOGO OF HARRIS BANK]

                        Harris Trust and Savings Bank
                           111 West Monroe Street
                           Chicago, Illinois 60603

of Chicago, Illinois, And Foreign and Domestic Subsidiaries, at the close of
business on September 30, 1998, a state banking institution organized and
operating under the banking laws of this State and a member of the Federal
Reserve System. Published in accordance with a call made by the Commissioner
of Banks and Trust Companies of the State of Illinois and by the Federal
Reserve Bank of this District.

                       Bank's Transit Number 71000288

<TABLE>
<CAPTION>
                                                                                                          THOUSANDS
                                         ASSETS                                                           OF DOLLARS
<S>                                                                                     <C>              <C>
Cash and balances due from depository institutions:
        Non-interest bearing balances and currency and coin.......................                       $ 1,097,714
        Interest bearing balances.................................................                       $   213,712
Securities:.......................................................................
a.  Held-to-maturity securities                                                                          $         0
b.  Available-for-sale securities                                                                        $ 5,036,734
Federal funds sold and securities purchased under agreements to resell                                   $    48,950
Loans and lease financing receivables:
        Loans and leases, net of unearned income..................................      $ 9,111,098
        LESS:  Allowance for loan and lease losses................................      $   104,900
                                                                                        -----------
        Loans and leases, net of unearned income, allowance, and reserve
        (item 4.a minus 4.b)......................................................                       $ 9,006,198
Assets held in trading accounts...................................................                       $   202,008
Premises and fixed assets (including capitalized leases)..........................                       $   245,290
Other real estate owned...........................................................                       $       365
Investments in unconsolidated subsidiaries and associated companies...............                       $        41
Customer's liability to this bank on acceptances outstanding......................                       $    34,997
Intangible assets.................................................................                       $   260,477
Other assets......................................................................                       $ 1,148,163
                                                                                                         -----------
TOTAL ASSETS                                                                                             $17,294,649
                                                                                                         ===========
</TABLE>


                                       3
                                       
<PAGE>   5

<TABLE>
<CAPTION>

                                            LIABILITIES
<S>                                                                                                  <C>             <C>
Deposits:                                                                                                       
   In domestic offices........................................................................                       $9,467,895
        Non-interest bearing..................................................................       $2,787,471
        Interest bearing......................................................................       $6,680,424
   In foreign offices, Edge and Agreement subsidiaries, and IBF's.............................                       $1,268,759
        Non-interest bearing..................................................................       $   23,329
        Interest bearing......................................................................       $1,245,430
Federal funds purchased and securities sold under agreements to repurchase in domestic                          
offices of the bank and of its Edge and Agreement subsidiaries, and in IBF's:                                   
Federal funds purchased & securities sold under agreements to repurchase......................                       $3,118,548
Trading Liabilities                                                                                                     110,858
Other borrowed money:.........................................................................                  
a.  With remaining maturity of one year or less                                                                      $1,202,050
b.  With remaining maturity of more than one year                                                                            $0
Bank's liability on acceptances executed and outstanding                                                                $34,997
Subordinated notes and debentures.............................................................                         $225,000
Other liabilities.............................................................................                         $530,224
                                                                                                                 -------------- 
TOTAL LIABILITIES                                                                                                   $15,958,331
                                           EQUITY CAPITAL                                                        ==============
Common stock..................................................................................                         $100,000
Surplus.......................................................................................                         $604,834
a.  Undivided profits and capital reserves....................................................                         $580,271
b.  Net unrealized holding gains (losses) on available-for-sale securities                                              $51,213
                                                                                                                 --------------
TOTAL EQUITY CAPITAL                                                                                                 $1,336,318
                                                                                                                 ==============
Total liabilities, limited-life preferred stock, and equity capital...........................                      $17,294,649
                                                                                                                 ==============
</TABLE>

     I, Pamela Piarowski, Vice President of the above-named bank, do hereby
declare that this Report of Condition has been prepared in conformance with
the instructions issued by the Board of Governors of the Federal Reserve
System and is true to the best of my knowledge and belief.

                               PAMELA PIAROWSKI
                                   10/29/98

     We, the undersigned directors, attest to the correctness of this Report
of Condition and declare that it has been examined by us and, to the best of
our knowledge and belief, has been prepared in conformance with the
instructions issued by the Board of Governors of the Federal Reserve System
and the Commissioner of Banks and Trust Companies of the State of Illinois and
is true and correct.

          EDWARD W. LYMAN,
          ALAN G. McNALLY,
          CHARLES SHAW
                                                                      Directors.

                                       4



<PAGE>   1
                                                                    EXHIBIT 26.2

      ___________________________________________________________________


                     SECURITIES AND EXCHANGE COMMISSION
                          Washington, D. C.  20549
                          _________________________

                                  FORM  T-1

                          STATEMENT OF ELIGIBILITY
                  UNDER THE TRUST INDENTURE ACT OF 1939 OF
                 A CORPORATION DESIGNATED TO ACT AS TRUSTEE
                 ___________________________________________
             CHECK IF AN APPLICATION TO DETERMINE ELIGIBILITY OF
              A TRUSTEE PURSUANT TO SECTION 305(b)(2) ________
                  ________________________________________

                          THE CHASE MANHATTAN BANK
             (Exact name of trustee as specified in its charter)


                                      
         NEW YORK                                           13-4994650
         (State of incorporation                      (I.R.S. employer
         if not a national bank)                   identification No.)

         270 PARK AVENUE
         NEW YORK, NEW YORK                                      10017
         (Address of principal executive offices)           (Zip Code)


                             William H. McDavid
                               General Counsel
                               270 Park Avenue
                          New York, New York 10017
                            Tel:  (212) 270-2611
          (Name, address and telephone number of agent for service)

                ____________________________________________
                           ILLINOIS POWER COMPANY
             (Exact name of obligor as specified in its charter)

                                      
         ILLINOIS                                           37-0988139
         (State or other jurisdiction of              (I.R.S. employer
         incorporation or organization)            identification No.)

         500 SOUTH 27TH STREET
         DECATUR, IL                                        62525-1805
         (Address of principal executive offices)           (Zip Code)

                ____________________________________________
                          UNSECURED DEBT SECURITIES
                     (Title of the indenture securities)

      ___________________________________________________________________

<PAGE>   2

                                   GENERAL

                                      
Item 1.  General Information.

         Furnish the following information as to the trustee:


         (a) Name and address of each examining or supervising authority to 
which it is subject.

             New York State Banking Department, State House, Albany, New York  
             12110.

             Board of Governors of the Federal Reserve System, Washington, 
             D.C., 20551

             Federal Reserve Bank of New York, District No. 2, 33 Liberty 
             Street, New York, N.Y.

             Federal Deposit Insurance Corporation, Washington, D.C., 20429.


         (b) Whether it is authorized to exercise corporate trust powers.

             Yes.



Item 2.  Affiliations with the Obligor.

         If the obligor is an affiliate of the trustee, describe each such 
         affiliation.

         None.



<PAGE>   3

Item 16.  List of Exhibits

          List below all exhibits filed as a part of this Statement of 
Eligibility.

          1.  A copy of the Articles of Association of the Trustee as now in 
effect, including the  Organization Certificate and the Certificates of         
Amendment dated February 17, 1969, August 31, 1977, December 31, 1980,
September 9, 1982, February 28, 1985, December 2, 1991 and July 10, 1996 (see
Exhibit 1 to Form T-1 filed in connection with Registration Statement  No.
333-06249, which is incorporated by reference).

          2.  A copy of the Certificate of Authority of the Trustee to Commence
Business (see Exhibit 2 to Form T-1 filed in connection with Registration
Statement No. 33-50010, which is incorporated by reference.  On July 14, 1996,
in connection with the merger of Chemical Bank and The Chase Manhattan Bank
(National Association), Chemical Bank, the surviving corporation, was renamed
The Chase Manhattan Bank).

          3.  None, authorization to exercise corporate trust powers being 
contained in the documents identified above as Exhibits 1 and 2.

          4.  A copy of the existing By-Laws of the Trustee (see Exhibit 4 to 
Form T-1 filed in connection with Registration Statement No. 333-06249, which is
incorporated by reference).

          5.  Not applicable.

          6.  The consent of the Trustee required by Section 321(b) of the Act 
(see Exhibit 6 to Form T-1 filed in connection with Registration Statement No.
33-50010, which is incorporated by reference. On July 14, 1996, in connection
with the merger of Chemical Bank and The Chase Manhattan Bank (National
Association), Chemical Bank, the surviving corporation, was renamed The Chase
Manhattan Bank).

          7.  A copy of the latest report of condition of the Trustee, published
pursuant to law or the requirements of its supervising or examining authority.

          8.  Not applicable.

          9.  Not applicable.

                                  SIGNATURE

          Pursuant to the requirements of the Trust Indenture Act of 1939 the
Trustee, The Chase Manhattan Bank, a corporation organized and existing under
the laws of the State of New York, has duly caused this statement of
eligibility to be signed on its behalf by the undersigned, thereunto duly
authorized, all in the City of New York and State of New York, on the 12th day
of January, 1999.

                                     THE CHASE MANHATTAN BANK

                                          By /s/ Gregory P. Shea      
                                             ------------------------- 
                                             Gregory P. Shea           
                                             Senior Trust Officer      

                                    - 3 -

<PAGE>   4

                             Exhibit 7 to Form T-1
                                        
                                        
                                Bank Call Notice
                                        
                             RESERVE DISTRICT NO. 2
                      CONSOLIDATED REPORT OF CONDITION OF
                                        
                            The Chase Manhattan Bank
                  of 270 Park Avenue, New York, New York 10017
                     and Foreign and Domestic Subsidiaries,
                    a member of the Federal Reserve System,
                                        
                at the close of business September 30, 1998, in
        accordance with a call made by the Federal Reserve Bank of this
        District pursuant to the provisions of the Federal Reserve Act.
                                        

<TABLE>
<CAPTION>
                                                                                DOLLAR AMOUNTS
                          ASSETS                                                   MILLIONS

<S>                                                                   <C>           <C>
Cash and balances due from depository institutions:
      Noninterest-bearing balances and
      currency and coin ..................................                          $11,951
      Interest-bearing balances ..........................                            4,551
Securities:  .............................................                  
Held to maturity securities...............................                            1,740
Available for sale securities.............................                           48,537
Federal funds sold and securities purchased under                                  
      agreements to resell ...............................                           29,730
Loans and lease financing receivables:                                      
      Loans and leases, net of unearned income............            $127,379
      Less: Allowance for loan and lease losses...........               2,719
      Less: Allocated transfer risk reserve ..............                   0
      Loans and leases, net of unearned income,                             
      allowance, and reserve .............................                          124,660
Trading Assets ...........................................                           51,549
Premises and fixed assets (including capitalized                            
      leases).............................................                            3,009
Other real estate owned ..................................                              272
Investments in unconsolidated subsidiaries and                              
      associated companies................................                              300
Customers' liability to this bank on acceptances                            
      outstanding ........................................                            1,329
Intangible assets ........................................                            1,429
Other assets .............................................                           13,563
                                                                                   -------- 
TOTAL ASSETS .............................................                         $292,620
                                                                                   ========
</TABLE>


                                     - 4 -


<PAGE>   5

                                  LIABILITIES

                                       
<TABLE>
<S>                                                             <C>         <C>
Deposits
      In domestic offices ..................................                $ 98,760
      Noninterest-bearing ..................................    $ 39,071
      Interest-bearing .....................................      59,689
                                                                --------    
      In foreign offices, Edge and Agreement,                   
      subsidiaries and IBF's................................                  75,403
      Noninterest-bearing ..................................    $  3,877
      Interest-bearing .....................................      71,526
                                                                         
Federal funds purchased and securities sold under agreements             
to repurchase ..............................................                  34,471
Demand notes issued to the U.S. Treasury ...................                   1,000
Trading liabilities ........................................                  41,589
                                                                         
Other borrowed money (includes mortgage indebtedness                     
      and obligations under capitalized leases):                         
      With a remaining maturity of one year or less ........                   3,781
      With a remaining maturity of more than one year                    
          through three years...............................                     213
      With a remaining maturity of more than three years....                     104
Bank's liability on acceptances executed and outstanding....                   1,329
Subordinated notes and debentures ..........................                   5,408
Other liabilities ..........................................                  12,041
                                                                         
TOTAL LIABILITIES ..........................................                 274,099
                                                                            --------
                                 EQUITY CAPITAL                          
                                                                         
Perpetual preferred stock and related surplus...............                       0
Common stock ...............................................                   1,211
Surplus  (exclude all surplus related to preferred stock)...                  10,441
Undivided profits and capital reserves .....................                   6,287
Net unrealized holding gains (losses)                                    
on available-for-sale securities ...........................                     566
Cumulative foreign currency translation adjustments ........                      16
                                                                         
TOTAL EQUITY CAPITAL .......................................                  18,521
                                                                            --------
TOTAL LIABILITIES AND EQUITY CAPITAL .......................                $292,620
                                                                            ========
</TABLE>

I, Joseph L. Sclafani, E.V.P. & Controller of the above-named bank, do
hereby declare that this Report of Condition has been prepared in
conformance with the instructions issued by the appropriate Federal
regulatory authority and is true to the best of my knowledge and
belief.

                                        JOSEPH L. SCLAFANI

We, the undersigned directors, attest to the correctness of this
Report of Condition and declare that it has been examined by us, and
to the best of our knowledge and belief has been prepared in
conformance with the instructions issued by the appropriate Federal
regulatory authority and is true and correct.


                                        WALTER V. SHIPLEY       )
                                        THOMAS G. LABRECQUE     )    DIRECTORS
                                        WILLIAM B. HARRISON, JR.)


                                      -5-




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