TETRA TECH INC
10-Q, 1999-08-18
ENGINEERING SERVICES
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<PAGE>

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-Q

(Mark One)
   [ X ]   QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934

           For the quarterly period ended JULY 4, 1999

                                       OR

   [   ]   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934

           For the transition period from ____________ to ____________

                         Commission File Number 0-19655

                                TETRA TECH, INC.
        ----------------------------------------------------------------
             (Exact name of registrant as specified in its charter)


           DELAWARE                                   95-4148514
- --------------------------------           -------------------------------
(State or other jurisdiction of            (I.R.S. Employer Identification
incorporation or organization)                          number)



              670 N. ROSEMEAD BOULEVARD, PASADENA, CALIFORNIA 91107
        -----------------------------------------------------------------
                    (Address of principal executive offices)


                                 (626) 351-4664
              ----------------------------------------------------
              (Registrant's telephone number, including area code)


                                 NOT APPLICABLE
              ----------------------------------------------------
              (Former name, former address and former fiscal year,
                          if changed since last report)


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter periods that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. Yes X   No
                                      ---    ---

As of August 6, 1999, the total number of outstanding shares of the Registrant's
common stock was 38,138,176.


<PAGE>

                                TETRA TECH, INC.

                                      INDEX

<TABLE>
<CAPTION>
                                                                        PAGE NO.
PART I.      FINANCIAL INFORMATION
<S>                                                                     <C>
    Item 1.  Financial Statements

                  Condensed Consolidated Balance Sheets                      3

                  Condensed Consolidated Statements of Income                4

                  Condensed Consolidated Statements of Cash Flows            5

                  Notes to Condensed Consolidated Financial Statements       9

    Item 2.  Management's Discussion and Analysis of
               Financial Condition and Results of Operations                15

    Item 3.  Quantitative and Qualitative Disclosures About Market Risk     22

             Risk Factors                                                   23


PART II.     OTHER INFORMATION

    Item 2.  Changes in Securities and Use of Proceeds                      30

    Item 6.  Exhibits and Reports on Form 8-K                               30


Signatures                                                                  35
</TABLE>

                                      -2-
<PAGE>

                          PART I. FINANCIAL INFORMATION
ITEM 1.
                                Tetra Tech, Inc.
                      Condensed Consolidated Balance Sheets

<TABLE>
<CAPTION>
In thousands, except share data                                                    July 4,     October 4,
                                                                                    1999          1998
                                                                                 ----------    ----------
                                                                                (unaudited)
                                                    ASSETS
<S>                                                                             <C>            <C>
CURRENT ASSETS:
    Cash and cash equivalents .................................................. $    9,293    $    4,889
    Accounts receivable - net ..................................................     80,041        68,834
    Unbilled receivables - net .................................................     69,622        59,888
    Prepaid and other current assets ...........................................      9,227         4,955
    Deferred income taxes ......................................................      3,766         3,766
                                                                                 ----------    ----------
       Total Current Assets ....................................................    171,949       142,332
                                                                                 ----------    ----------

PROPERTY AND EQUIPMENT:
    Leasehold improvements .....................................................      2,121         1,348
    Equipment, furniture and fixtures ..........................................     34,760        25,616
                                                                                 ----------    ----------
       Total ...................................................................     36,881        26,964
    Accumulated depreciation and amortization ..................................    (18,578)      (13,219)
                                                                                 ----------    ----------
PROPERTY AND EQUIPMENT - NET ...................................................     18,303        13,745
                                                                                 ----------    ----------

INTANGIBLE ASSETS - NET ........................................................    147,762       108,638
LOAN TO UNCONSOLIDATED AFFILIATE ...............................................      3,000            --
OTHER ASSETS ...................................................................      4,014         1,895
                                                                                 ----------    ----------

TOTAL ASSETS ................................................................... $  345,028    $  266,610
                                                                                 ----------    ----------
                                                                                 ----------    ----------

                                        LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
    Accounts payable ........................................................... $   25,195    $   24,027
    Accrued compensation .......................................................     19,597        15,614
    Other current liabilities ..................................................     16,226         8,283
    Current portion of long-term obligations ...................................     21,000        14,065
    Income taxes payable .......................................................      5,953         3,294
                                                                                 ----------    ----------
       Total Current Liabilities ...............................................     87,971        65,283
                                                                                 ----------    ----------

LONG-TERM OBLIGATIONS ..........................................................     35,336        33,546
                                                                                 ----------    ----------

COMMITMENTS AND CONTINGENCIES

STOCKHOLDERS' EQUITY:
    Preferred stock - authorized, 2,000,000 shares of $.01 par value;
      issued and outstanding 0 shares ..........................................         --            --
    Exchangeable stock of a subsidiary .........................................     13,570        15,411
    Common stock - authorized, 50,000,000 shares of $.01 par value; issued and
      outstanding 38,132,018 and 28,630,600 shares at
      July 4, 1999 and October 4, 1998, respectively ...........................        381           287
    Additional paid-in capital .................................................    123,444        87,565
    Cumulative translation loss ................................................       (584)           --
    Retained earnings ..........................................................     84,910        64,518
                                                                                 ----------    ----------
TOTAL STOCKHOLDERS' EQUITY .....................................................    221,721       167,781
                                                                                 ----------    ----------

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY ..................................... $  345,028    $  266,610
                                                                                 ----------    ----------
                                                                                 ----------    ----------
</TABLE>

     See accompanying Notes to Condensed Consolidated Financial Statements.

                                      -3-
<PAGE>

                                Tetra Tech, Inc.
                   Condensed Consolidated Statements of Income
                                   (Unaudited)

<TABLE>
<CAPTION>

In thousands, except per share data                                    Three Months Ended         Nine Months Ended
                                                                     ----------------------    ----------------------
                                                                       July 4,     June 28,     July 4,      June 28,
                                                                        1999        1998         1999          1998
                                                                     ---------    ---------    ---------    ---------
<S>                                                                  <C>          <C>          <C>          <C>
Gross Revenue ....................................................   $ 157,091    $  98,231    $ 399,147    $ 257,396
      Subcontractor costs ........................................      36,352       23,082       92,208       56,777
                                                                     ---------    ---------    ---------    ---------
Net Revenue ......................................................     120,739       75,149      306,939      200,619

Cost of Net Revenue ..............................................      88,189       54,405      232,778      149,530
                                                                     ---------    ---------    ---------    ---------
Gross Profit .....................................................      32,550       20,744       74,161       51,089

Selling, General and Administrative Expenses .....................      15,598        8,636       33,120       21,605
Amortization of Intangibles ......................................       1,353          697        3,386        2,022
                                                                     ---------    ---------    ---------    ---------
Income from Operations ...........................................      15,599       11,411       37,655       27,462

Interest Expense .................................................         649          624        2,143        1,433
Interest Income ..................................................         (99)        (114)        (362)        (254)
                                                                     ---------    ---------    ---------    ---------

Income Before Minority Interest and Income Tax
   Expense .......................................................      15,049       10,901       35,874       26,283
Income to Minority Interest ......................................          --        1,194           --        1,397
                                                                     ---------    ---------    ---------    ---------
Income Before Income Tax Expense .................................      15,049        9,707       35,874       24,886

Income Tax Expense ...............................................       6,546        4,214       15,482       10,822
                                                                     ---------    ---------    ---------    ---------

Net Income .......................................................   $   8,503    $   5,493    $  20,392    $  14,064
                                                                     ---------    ---------    ---------    ---------
                                                                     ---------    ---------    ---------    ---------

Basic Earnings Per Share .........................................   $    0.22    $    0.16    $    0.55    $    0.41
                                                                     ---------    ---------    ---------    ---------
                                                                     ---------    ---------    ---------    ---------

Diluted Earnings Per Share .......................................   $    0.21    $    0.15    $    0.52    $    0.39
                                                                     ---------    ---------    ---------    ---------
                                                                     ---------    ---------    ---------    ---------

Weighted Average Common Shares Outstanding:
      Basic ......................................................      37,801       35,184       36,805       34,695
                                                                     ---------    ---------    ---------    ---------
                                                                     ---------    ---------    ---------    ---------

      Diluted ....................................................      40,145       36,502       39,266       36,245
                                                                     ---------    ---------    ---------    ---------
                                                                     ---------    ---------    ---------    ---------
</TABLE>

     See accompanying Notes to Condensed Consolidated Financial Statements.


                                      -4-
<PAGE>

                                Tetra Tech, Inc.
                 Condensed Consolidated Statements of Cash Flow
                                   (Unaudited)
<TABLE>
<CAPTION>
In thousands                                                                            Nine Months Ended
                                                                                 -------------------------------
                                                                                   July 4,            June 28,
                                                                                    1999                1998
                                                                                 ------------       ------------
<S>                                                                              <C>                <C>
CASH FLOWS FROM OPERATING ACTIVITIES:

Net income..................................................................       $ 20,392         $   14,064

Adjustments to reconcile net income to net cash provided by operating
   activities:
      Depreciation and amortization.........................................          8,745              5,102
      Undistributed earnings to minority interest...........................            --               1,397
      Provision for losses on receivables...................................         (1,105)              (631)

Changes in operating assets and liabilities, net of effects of acquisitions:
      Accounts receivable...................................................          2,220            (16,655)
      Unbilled receivables..................................................         (3,446)             1,074
      Prepaid and other assets..............................................         (3,906)            (4,981)
      Accounts payable......................................................         (5,494)             4,937
      Accrued compensation..................................................             26               (304)
      Other current liabilities.............................................            170             (4,511)
      Income taxes payable..................................................           (824)            (1,346)
                                                                                 ------------       ------------
          Net Cash Provided By (Used In) Operating Activities...............         16,778             (1,854)
                                                                                 ------------       ------------

CASH FLOWS FROM INVESTING ACTIVITIES:

Capital expenditures........................................................         (4,005)            (2,374)
Payments for business acquisitions, net of cash acquired....................        (33,963)           (25,948)
Payments on loans to unconsolidated affiliate...............................         (3,000)                --
                                                                                 ------------       ------------
          Net Cash Used In Investing Activities.............................        (40,968)            (28,322)
                                                                                 ------------       ------------

CASH FLOWS FROM FINANCING ACTIVITIES:

Payments on long-term debt..................................................        (45,000)            (27,519)
Proceeds from issuance of long-term debt....................................         48,359              49,000
Net proceeds from issuance of common stock..................................         25,819               3,305
                                                                                 ------------       ------------
          Net Cash Provided By Financing Activities.........................         29,178              24,786
                                                                                 ------------       ------------

EFFECT OF RATE CHANGES ON CASH..............................................           (584)                 --
                                                                                 ------------       ------------

NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS........................          4,404             (5,390)
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD............................          4,889             12,262
                                                                                 ------------       ------------
CASH AND CASH EQUIVALENTS AT END OF PERIOD..................................     $    9,293         $    6,872
                                                                                 ------------       ------------
                                                                                 ------------       ------------

SUPPLIMENTAL CASH FLOW INFORMATION:
Cash paid during the period for:
      Interest..............................................................     $    1,804         $    1,197
      Income taxes..........................................................     $    4,739         $   12,168
</TABLE>


                                   (Continued)

                                      -5-
<PAGE>

                                Tetra Tech, Inc.
                 Condensed Consolidated Statements of Cash Flow
                                   (Unaudited)

<TABLE>
<CAPTION>
In thousands                                                                                Nine Months Ended
                                                                                        -----------------------
                                                                                          July 4,     June 28,
                                                                                           1999         1998
                                                                                        ----------   ----------
<S>                                                                                     <C>          <C>
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING
   ACTIVITIES:
   In February 1999, the Company purchased all of the capital stock of McCulley,
     Frick & Gilman, Inc. In conjunction with this acquisition, liabilities were
     assumed as follows:
        Fair value of assets acquired ...............................................   $   10,086
        Cash paid ...................................................................       (4,250)
        Issuance of common stock ....................................................       (3,613)
        Other acquisition costs .....................................................          (70)
                                                                                        ----------
           Liabilities assumed ......................................................   $    2,153
                                                                                        ----------
                                                                                        ----------

   In May 1999, the Company purchased all of the capital stock of Collins/Pina
     Consulting Engineers, Inc. In conjunction with this acquisition,
     liabilities were assumed as follows:
        Fair value of assets acquired ...............................................   $    4,919
        Cash paid ...................................................................       (2,501)
        Issuance of common stock ....................................................         (102)
        Other acquisition costs .....................................................          (70)
                                                                                        ----------
           Liabilities assumed ......................................................   $    2,246
                                                                                        ----------
                                                                                        ----------

   In May 1999, the Company purchased all of the capital stock of
     D.E.A. Construction Company.  In conjunction with this acquisition,
      liabilities were assumed as follows:
        Fair value of assets acquired ...............................................   $   19,532
        Cash paid ...................................................................      (14,000)
        Covenant not to compete .....................................................         (250)
        Purchase price payable ......................................................         (185)
        Other acquisition costs .....................................................          (80)
                                                                                        ----------
           Liabilities assumed ......................................................   $    5,017
                                                                                        ----------
                                                                                        ----------

   In May 1999, the Company purchased all of the capital stock of BAHA
     Communications, Inc. In conjunction with this acquisition, liabilities were
     assumed as follows:
        Fair value of assets acquired ...............................................   $    3,355
        Issuance of common stock ....................................................       (2,133)
        Common stock held in escrow .................................................         (425)
        Other acquisition costs .....................................................          (70)
                                                                                        ----------
           Liabilities assumed ......................................................   $      727
                                                                                        ----------
                                                                                        ----------
</TABLE>


                                   (Continued)

                                      -6-

<PAGE>

                                Tetra Tech, Inc.
                 Condensed Consolidated Statements of Cash Flow
                                   (Unaudited)
<TABLE>
<CAPTION>
In thousands                                                                             Nine Months Ended
                                                                                    --------------------------
                                                                                     July 4,          June 28,
                                                                                       1999            1998
                                                                                    ----------      ----------
<S>                                                                                 <C>             <C>
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING
   ACTIVITIES:
   In June 1999, the Company purchased all of the capital stock of Utilities &
     C.C., Inc. In conjunction with this acquisition, liabilities were assumed
     as follows:
        Fair value of assets acquired ...........................................   $    2,568
        Issuance of common stock ................................................       (2,040)
        Other acquisition costs .................................................          (70)
                                                                                    ----------
           Liabilities assumed ..................................................   $      458
                                                                                    ----------
                                                                                    ----------

   In June 1999, the Company purchased all of the capital stock of ASL
     Consultants, Inc. In conjunction with this acquisition, liabilities were
     assumed as follows:
        Fair value of assets acquired ...........................................   $   16,433
        Cash paid ...............................................................      (10,000)
        Other acquisition costs .................................................          (90)
                                                                                    ----------
           Liabilities assumed ..................................................   $    6,343
                                                                                    ----------
                                                                                    ----------

   In June 1999, the Company purchased all of the capital stock of L.M.W.
     Associates, Inc., Cosentini Associates, Inc. and Cobin, Inc. and all of the
     limited liability partnership interests of Cosentini Associates IL LLP,
     Cosentini Associates MA LLP, Cosentini Associates DC LLP and Cosentini
     Associates FL LLP (collectively, CAA). In conjunction with these acquisitions,
     liabilities were assumed as follows:
        Fair value of assets acquired ...........................................   $   15,577
        Cash paid ...............................................................       (5,069)
        Other acquisition costs .................................................         (250)
                                                                                    ----------
           Liabilities assumed ..................................................   $   10,258
                                                                                    ----------
                                                                                    ----------

   In December 1997, the Company, through its wholly-owned subsidiary Tetra Tech
     NUS, Inc., purchased the assets of certain environmental services
     businesses of Brown & Root, Inc. and Halliburton NUS Corporation, both of
     which were subsidiaries of Halliburton Company. In conjunction with this
     acquisition, liabilities were assumed as follows:
        Fair value of assets acquired ...........................................                   $   27,794
        Cash paid ...............................................................                      (24,872)
        Other acquisition costs .................................................                         (325)
                                                                                                    ----------
           Liabilities assumed ..................................................                   $    2,597
                                                                                                    ----------
                                                                                                    ----------
</TABLE>



                                   (Continued)

                                      -7-
<PAGE>

                                Tetra Tech, Inc.
                 Condensed Consolidated Statements of Cash Flow
                                   (Unaudited)
<TABLE>
<CAPTION>
In thousands                                                                            Nine Months Ended
                                                                                  ------------------------------
                                                                                    July 4,           June 28,
                                                                                     1999               1998
                                                                                  -----------       -----------
<S>                                                                               <C>               <C>
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING
   ACTIVITIES:
   In March 1998, the Company, through its wholly-owned subsidiary Whalen
     Service Corps Inc., purchased certain assets of TANCO LLC, dba Integration
     Technologies from ANTEC Corporation. This purchase was related to a limited
     liability company agreement between Whalen Service Corps Inc. and Sentrex
     Cen-Comm. In conjunction with this acquisition, liabilities were assumed as
     follows:
        Fair value of assets acquired.......................................                        $    1,572
        Cash paid...........................................................                              (623)
                                                                                                    -----------
           Liabilities assumed..............................................                        $      949
                                                                                                    -----------
                                                                                                    -----------

   In March 1998, the Company purchased all of the capital stock of
     C.D.C. Engineering, Inc.  In conjunction with this acquisition,
     liabilities were assumed as follows:
        Fair value of assets acquired.......................................                        $    2,299
        Cash paid...........................................................                              (323)
        Issuance of common stock............................................                            (1,294)
        Other acquisition costs.............................................                               (70)
                                                                                                    -----------
           Liabilities assumed..............................................                        $      612
                                                                                                    -----------
                                                                                                    -----------
</TABLE>


     See accompanying Notes to Condensed Consolidated Financial Statements.

                                   (Concluded)

                                      -8-
<PAGE>

                                TETRA TECH, INC.

              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

1.       BASIS OF PRESENTATION

         The accompanying condensed consolidated balance sheet as of July 4,
1999, the condensed consolidated statements of income for the three-month and
nine-month periods ended July 4, 1999 and June 28, 1998 and the condensed
consolidated statements of cash flows for the nine-month periods ended July 4,
1999 and June 28, 1998 are unaudited, and in the opinion of management include
all adjustments, consisting of only normal and recurring adjustments, necessary
for a fair presentation of the financial position and the results of operations
for the periods presented.

         The condensed consolidated financial statements should be read in
conjunction with the consolidated financial statements and notes thereto
included in the Company's Annual Report on Form 10-K for the fiscal year ended
October 4, 1998.

         The results of operations for the three and nine months ended July 4,
1999 are not necessarily indicative of the results to be expected for the fiscal
year ending October 3, 1999.

         All share and per share amounts reflect, on a retroactive basis, the
5-for-4 stock splits effected in the form of 25.0% stock dividends, wherein one
additional share of stock was issued on June 15, 1999 and September 15, 1998 for
each four shares outstanding as of the record dates of May 14, 1999 and July 27,
1998, respectively.

2.       EARNINGS PER SHARE

         Due to the Company's complex capital structure, the Company presents
both basic and diluted Earnings Per Share (EPS). Basic EPS excludes dilution and
is computed by dividing income available to common stockholders by the weighted
average number of common shares outstanding for the period. Diluted EPS is
computed by dividing net income by the weighted average number of common shares
outstanding and dilutive potential common shares. The Company includes as
potential common shares the weighted average number shares of exchangeable stock
of a subsidiary and the weighted average dilutive effects of outstanding stock
options. The exchangeable stock of a subsidiary is non-voting and is
exchangeable, on a basis of 1.25 shares of exchangeable stock for 1 share of
Company common stock.

3.       CURRENT ASSETS

         The Company considers all highly liquid investments purchased with a
maturity of three months or less to be cash equivalents. Cash and cash
equivalents totaled $9.3 million and $4.9 million at July 4, 1999 and October 4,
1998, respectively.


                                      -9-
<PAGE>

4.       MERGERS AND ACQUISITIONS

         On December 31, 1997, the Company acquired, through its wholly-owned
subsidiary Tetra Tech NUS, Inc., the assets of certain environmental services
businesses of Brown & Root, Inc. and Halliburton Corporation, both of which are
subsidiaries of Halliburton Company (collectively, NUS). NUS provides
consulting, engineering and design services for the environmental remediation of
contaminated air, water and soil conditions. The purchase price was valued at
approximately $25.2 million, as adjusted, and consisted of cash.

         On March 2, 1998, Whalen Service Corps Inc. (WSC) agreed to participate
in a partnership with Sentrex Cen-Comm and ANTEC Corporation to provide design,
engineering, information management and construction services to support
advanced communication system upgrades to the broadband information transport
industries. The agreement required the purchase of certain assets of TANCO LLC
from ANTEC Corporation for a price in cash of approximately $0.6 million. WSC
initially held a 51.0% majority interest in Whalen/Sentrex LLC, a California
limited liability company, while LAL Corp. held the remaining 49.0% minority
interest.

         On March 26, 1998, the Company acquired 100.0% of the capital stock of
C.D.C. Engineering, Inc. (CDE), a consulting and engineering firm specializing
in civil engineering, transportation engineering, structural engineering and
land surveying. The purchase has been valued at approximately $1.6 million,
consisting of cash and 88,829 shares of Company common stock.

         On July 8, 1998, the Company acquired 100.0% of the capital stock of
McNamee, Porter & Seeley, Inc. (MPS), a provider of engineering services with
expertise in the areas of water, industrial wastewater and process controls. The
purchase was valued at approximately $15.3 million, consisting of cash and
343,610 shares of Company common stock. Simultaneously with the acquisition, MPS
distributed to its former shareholders accounts receivable having a net value of
$8.0 million.

         On September 22, 1998, the Company acquired, through its subsidiary
Tetra Tech Canada Ltd. (TtC), 100.0% of the capital stock of 1056584 Ontario
Limited, 1056585 Ontario Limited, Venture Cable Limited, Cen-Comm
Communications, Inc., Sentrex Electronics Inc. and LAL Corp. (collectively,
the Sentrex Group of Companies (SGOC)), providers of engineering and
technical services to the cable television, telephony and data networking
industries. The purchase has been valued at approximately $19.2 million,
consisting of cash and 1,150,442 shares of TtC exchangeable stock. The TtC
exchangeable stock is exchangeable, on a basis of 1.25 shares of exchangeable
stock for 1 share of Company common stock as described in the related
purchase agreement. Upon completion of the SGOC acquisition, the Company
beneficially owns 100.0% of Whalen/Sentrex LLC.

         On February 26, 1999, the Company acquired 100.0% of the capital stock
of McCulley, Frick & Gilman, Inc. (MFG), a provider of professional
environmental science and consulting services to private-sector clients. The
purchase was valued at approximately $7.9 million, consisting of cash and
231,490 shares of Company common stock, and is subject to a purchase


                                      -10-
<PAGE>

price and purchase allocation adjustment based on the final determination of
MFG's net asset value as of February 26, 1999.

         On May 7, 1999, the Company acquired 100.0% of the capital stock of
Collins/Pina Consulting Engineers, Inc. (CPC), a provider of consulting
engineering and related services primarily in the state of Arizona. The purchase
was valued at approximately $2.7 million, as adjusted, consisting of cash and
6,172 shares of Company common stock.

         On May 19, 1999, the Company acquired 100.0% of the capital stock of
D.E.A. Construction Company (DCC), a provider of engineering and network
infrastructure services for cable television and fiber optic telephone networks
including design and construction and maintenance capabilities of communications
and information transport systems. The purchase was valued at approximately
$14.3 million and consisted of cash and is subject to a purchase price and
purchase allocation adjustment based on the final determination of DCC's net
asset value as of May 19, 1999. Additionally, the Company paid $0.3 million to
the President and Chief Executive Officer of DCC as consideration for a
non-competition agreement.

         On May 21, 1999, the Company acquired 100.0% of the capital stock of
BAHA Communications, Inc. (BCI), a supplier of infrastructure installation and
maintenance services to the wireless personal communications industry. The
purchase was valued at approximately $2.6 million and consisted of 176,168
shares of Company common stock and is subject to a purchase price and purchase
allocation adjustment based on the final determination of BCI's net asset value
as of June 30, 1999. Of the 176,168 shares of Company common stock, 29,272
shares are being held in escrow as contingent consideration until July 31, 2000
and will be released dependent upon BCI's operational performance, as specified
in the related escrow agreement, during the previous 12-month period.
Simultaneously with the acquisition, BCI distributed to its former shareholders
accounts receivable having a net value of $1.0 million.

         On June 18, 1999, the Company acquired 100.0% of the capital stock of
Utilities & C.C., Inc. (UCC), a supplier of infrastructure installation and
maintenance services to the wireless personal communications industry. The
purchase was valued at approximately $2.1 million and consisted of 137,930
shares of Company common stock and is subject to a purchase price and purchase
allocation adjustment based upon the final determination of UCC's net asset
value as of May 30, 1999.

         On June 25, 1999, the Company acquired 100.0% of the capital stock of
ASL Consultants, Inc. (ASL), a provider of water and wastewater treatment,
transportation, and other engineering services. The purchase was valued at
approximately $10.1 million and consisted of cash and is subject to a purchase
price and purchase allocation adjustment based upon the final determination of
ASL's net asset value as of July 2, 1999.

         On June 30, 1999, the Company acquired 100.0% of the capital stock
of L.M.W. Associates, Inc., Cosentini Associates, Inc. and Cobin, Inc., and
100.0% of the limited liability partnership interests of Cosentini Associates
IL LLP, Cosentini Associates MA LLP, Cosentini Associates DC LLP and
Cosentini Associates FL LLP (collectively, CAA). The purchase was valued at
approximately $5.3 million and consisted of cash and is subject to a purchase
price and

                                      -11-
<PAGE>

purchase allocation adjustment based upon the final determination of CAA's net
asset value as of June 30, 1999. Simultaneously with the acquisition, CAA
distributed to its former shareholders and partners accounts receivable having a
gross value of $18.4 million.

         All of the acquisitions above have been accounted for as purchases
and, accordingly, the purchase prices of the businesses acquired have been
allocated to the assets and liabilities acquired based upon their fair
values. The excess of the purchase cost of the acquisitions over the fair
value of the net assets acquired was recorded as goodwill and is included in
Intangible Assets - Net in the accompanying balance sheets. The Company
values stock exchanged in acquisitions based on extended restriction periods
and economic factors specific to the Company's circumstances. During fiscal
1998 and 1999, stock exchanged in acquisitions was discounted by 15.0%. The
results of operations of each of the companies acquired have been included in
the Company's financial statements as set forth in the related purchase
agreements.

         The effect of unaudited pro forma operating results of the UCC, BCI,
DCC, CPC, MFG, SGOC and CDE transactions, had they been acquired on September
29, 1997, is not material.

         Pro forma operating results assuming the Company had acquired CAA, ASL,
MPS and NUS on September 29, 1997 is presented in Note 6. UNAUDITED PRO FORMA
OPERATING RESULTS.

5.       ACCOUNTS RECEIVABLE

         Accounts receivable are presented net of a valuation allowance to
provide for doubtful accounts and for the potential disallowance of billed and
unbilled costs. The allowance for doubtful accounts as of July 4, 1999 and
October 4, 1998 was $3.6 million and $2.9 million, respectively. The allowance
for disallowed costs as of July 4, 1999 and October 4, 1998 was $3.7 million and
$9.8 million, respectively. Disallowance of billed and unbilled costs is
primarily associated with contracts with the Federal government which contain
clauses that subject contractors to several levels of audit. The Company
establishes reserves on those contract receivables, especially those acquired in
acquisitions, where there is substantial uncertainty as to their collection. In
September 1995, the Company purchased the stock of PRC Environmental Management,
Inc. (EMI). EMI contracts with the Federal government and at the time of
acquisition, had outstanding audits for the years 1987 through 1995. Reserves
for cost disallowances resulting from those audits were established at the time
of acquisition. During the three months ended July 4, 1999, it was determined
that approximately $4.4 million of the $10.7 million outstanding receivables
relating to these years would ultimately be uncollectible due to cost
disallowances. Accordingly, this amount was applied against the allowance for
disallowed costs. It was further determined that the total reserve against these
receivables exceeded the ultimate risk exposure by approximately $1.75 million.
Accordingly, this amount was taken into income during the three months ended
July 4, 1999. At July 4, 1999, approximately $2.1 million of these receivables
remained uncollected and fully reserved. Should these amounts be collected in
future periods, they will likewise be taken into income. However, as of July 4,
1999, collectibility was not assured and therefore these amounts remain fully
reserved. Management believes that resolution of these matters will not have a
material adverse impact on the Company's financial position or results of
operations.


                                      -12-
<PAGE>

6.       UNAUDITED PRO FORMA OPERATING RESULTS

         The table below presents summarized unaudited pro forma operating
results assuming that the Company had acquired CAA, ASL, MPS and NUS on
September 29, 1997. These amounts are based on historical results and
assumptions and estimates which the Company believes to be reasonable. The pro
forma results do not reflect anticipated cost savings and do not necessarily
represent results which would have occurred if the CAA, ASL, MPS and NUS
acquisitions had actually taken place on September 29, 1997.
<TABLE>
<CAPTION>
                                                      Pro Forma Nine Months Ended
                                                  -------------------------------------
                                                  July 4, 1999            June 28, 1998
                                                 -------------            -------------
         <S>                                     <C>                      <C>
         Gross revenue                              $429,420                 $344,030
         Income from operations                       39,139                   29,774
         Net income                                   36,709                   14,055
         Basic earnings per share                       0.57                     0.40
         Diluted earnings per share                     0.53                     0.39
         Weighted average shares outstanding:
              Basic                                   36,805                   34,954
              Diluted                                 39,265                   36,507
</TABLE>

7.       COMPREHENSIVE INCOME

         Comprehensive income is the change in equity of a business enterprise
during a period from transactions and other events and circumstances from non
owner sources. These sources include net income and other revenues, expenses,
gains and losses incurred. The Company includes as other comprehensive income
translation gains and losses from subsidiaries with functional currencies
different than that of the Company. For the three and nine months ended July 4,
1999, comprehensive income was approximately $8.7 million and $19.8 million,
respectively. For the three and nine months ended July 4, 1999, the Company
incurred net translation gains of $0.2 million and net translation losses of
$0.6 million, respectively. The Company incurred no translation gains or losses
for the three and nine months ended June 28, 1998.

8.       LOAN TO UNCONSOLIDATED AFFILIATE

         During the nine months ended July 4, 1999, the Company had loans of
$3.0 million outstanding to TANCO LLC, a 50% owned affiliate, for working
capital needs.

9.       SECONDARY OFFERING OF COMMON STOCK

         In February 1998, the Company, along with certain selling
stockholders, offered 3,968,750 shares of its common stock through a public
offering. The Company offered 1,250,000 shares and received approximately
$22.0 million in net proceeds from the offering of these shares. These
proceeds were used for the partial repayment of outstanding indebtedness
under the Company's revolving credit facility.

                                      -13-
<PAGE>

10.      SUBSEQUENT EVENTS

         Effective August 2, 1999, the Company amended its revolving credit
facility to increase its line of credit from $65.0 million to $80.0 million in
order to provide for additional working capital and potential acquisition needs.
This facility will be reduced to $65.0 million in February 2000.


                                      -14-
<PAGE>

ITEM 2.

                MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
                      CONDITION AND RESULTS OF OPERATIONS

         EXCEPT FOR THE HISTORICAL INFORMATION CONTAINED BELOW, THE MATTERS
DISCUSSED IN THIS SECTION ARE FORWARD-LOOKING STATEMENTS THAT INVOLVE A NUMBER
OF RISKS AND UNCERTAINTIES. OUR ACTUAL LIQUIDITY NEEDS, CAPITAL RESOURCES AND
OPERATING RESULTS MAY DIFFER MATERIALLY FROM THE DISCUSSION SET FORTH BELOW IN
THESE FORWARD-LOOKING STATEMENTS. FOR ADDITIONAL INFORMATION, REFER TO THE NOTES
TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS INCLUDED ELSEWHERE IN THIS
FILING.

OVERVIEW

         Tetra Tech, Inc. is a leading provider of specialized management
consulting and technical services in three principal business areas: resource
management, infrastructure and communications. As a specialized management
consultant, we assist our clients in defining problems and developing innovative
and cost-effective solutions. Our management consulting services are
complemented by our technical services. These technical services, which
implement solutions, include research and development, applied science,
engineering and architectural design, construction management, and operations
and maintenance. Our clients include a diverse base of public and private
organizations located in the United States and internationally.

         Since our initial public offering in December 1991, we have increased
the size and scope of our business and have expanded our service offerings
through a series of strategic acquisitions and internal growth.

         We derive our gross revenues from fees from professional services. Our
services are billed under various types of contracts with our clients,
including:

         -  Fixed-price;
         -  Fixed-rate time and materials;
         -  Cost-reimbursement plus fixed fee; and
         -  Cost-reimbursement plus fixed and award fee.

         In the course of providing our services, we routinely subcontract
services. These subcontractor costs are passed through to clients and, in
accordance with industry practice, are included in gross revenue. Because
subcontractor services can change significantly from project to project, we
believe net revenue, which is gross revenue less the cost of subcontractor
services, is a more appropriate measure of our performance.

         Our cost of net revenue includes professional compensation and certain
direct and indirect overhead costs such as rents, utilities and travel.
Professional compensation represents the majority of these costs. Our selling,
general and administrative (SG&A) expenses are comprised primarily of our
corporate headquarters' costs related to the executive offices, corporate
finance and accounting, information technology, marketing, and bid and proposal
costs. These costs are generally unrelated to specific client projects and can
vary as expenses are


                                      -15-
<PAGE>

incurred supporting corporate activities and initiatives. In addition, we
include amortization of certain intangible assets resulting from acquisitions in
SG&A expenses.

         We provide our services to a diverse base of Federal, state and local
government agencies, and commercial and international clients. The following
table presents, for the periods indicated, the approximate percentage of net
revenue attributable to these client sectors:

<TABLE>
<CAPTION>
                                                           Percentage of Net Revenue
                             -----------------------------------------------------------------------------------
                                        Three Months Ended                           Nine Months Ended
                             ---------------------------------------     ---------------------------------------
Client Sector                    July 4, 1999         June 28, 1998          July 4, 1999         June 28, 1998
- -------------                -------------------  -------------------    -------------------  ------------------
<S>                          <C>                  <C>                    <C>                  <C>
Federal government                   36.1%                51.5%                  39.6%                49.8%
State & local government             17.4                 11.4                   15.6                 12.1
Commercial                           44.1                 34.8                   41.0                 35.8
International                         2.4                  2.3                    3.8                  2.3
</TABLE>

RECENT ACQUISITIONS

         As a part of our growth strategy, we expect to pursue complementary
acquisitions to expand our geographical reach and the breadth and depth of our
service offerings. During fiscal 1999, we made the following acquisitions:

         MCCULLEY, FRICK & GILMAN, INC. -- In February 1999, we acquired
McCulley, Frick & Gilman, Inc. (MFG). The purchase was valued at approximately
$7.9 million. Following the transaction we changed the name to MFG, Inc. MFG, a
Colorado-based consulting and engineering firm, provides professional
environmental science and consulting services to private-sector clients
throughout the United States.

         COLLINS/PINA CONSULTING ENGINEERS, INC. -- In May 1999, we acquired
Collins/Pina Consulting Engineers, Inc. (CPC). The purchase was valued at
approximately $2.7 million. CPC, an Arizona-based consulting engineering firm,
provides engineering and related services primarily to state and local
governments in Arizona.

         D.E.A. CONSTRUCTION COMPANY -- In May 1999, we acquired D.E.A.
Construction Company (DCC). The purchase was valued at approximately $14.3
million. DCC, a Colorado-based construction and field services firm, provides
design and construction and maintenance of communications and information
transport systems to the communications industry primarily in Colorado, Idaho
and surrounding states.

         BAHA COMMUNICATIONS, INC. -- In May 1999, we acquired BAHA
Communications, Inc. (BCI). The purchase was valued at approximately $2.6
million. BCI, a Nevada-based construction and field services firm, provides
infrastructure installation and maintenance services to the wireless personal
communications industry primarily in Nevada and the Southwestern United States.

         UTILITIES & C.C., INC. -- In June 1999, we acquired Utilities & C.C.,
Inc. (UCC). The purchase was valued at approximately $2.1 million. UCC, a
Northern California-based construction and field services firm, provides
infrastructure installation and maintenance services to the wireless personal
communications industry primarily in California.


                                      -16-
<PAGE>

         ASL CONSULTANTS, INC. -- In June 1999, we acquired ASL Consultants,
Inc. (ASL). The purchase was valued at approximately $10.1 million. ASL, a
Southern California-based consulting engineering firm, provides water and
wastewater treatment, transportation, and other engineering services throughout
California and Arizona to Federal, state, and local government and commercial
clients.

         COSENTINI ASSOCIATES -- In June 1999, we acquired outstanding shares
and partnership interests of certain companies affiliated with Cosentini
Associates LLP (collectively, CAA). The purchase was valued at approximately
$5.3 million. CAA, a New York-based engineering firm, provides engineering
services for major buildings primarily in the Northeastern United States.

RESULTS OF OPERATIONS

         The following table presents the percentage relationship of selected
items to net revenue in our condensed consolidated statements of income:

<TABLE>
<CAPTION>
                                   % Relationship to Net Revenue               % Relationship to Net Revenue
                                   -----------------------------               -----------------------------
                                        Three Months Ended                           Nine Months Ended
                                        ------------------                           -----------------
                                  July 4, 1999    June 28, 1998               July 4, 1999    June 28, 1998
                                  ------------    -------------               ------------    -------------
<S>                               <C>             <C>                         <C>             <C>
Net revenue                          100.0%          100.0%                      100.0%          100.0%
Cost of net revenue                   73.0            72.4                        75.8            74.5
                                   ---------       ----------                 ----------       ----------
Gross profit                          27.0            27.6                        24.2            25.5
Selling, general and
   administrative expenses            12.9            11.5                        10.8            10.8
Acquisition amortization               1.2             0.9                         1.1             1.0
                                   ---------       ----------                 ----------       ----------
Income from operations                12.9            15.2                        12.3            13.7
Net interest (expense) income         (0.4)           (0.7)                       (0.6)           (0.6)
                                   ---------       ----------                 ----------       ----------
Income before minority interest
   and income tax expense             12.5            14.5                        11.7            13.1
Income to minority interest            --             (1.6)                        --             (0.7)
                                   ---------       ----------                 ----------       ----------
Income before income tax expense      12.5            12.9                        11.7            12.4
Income tax expense                     5.5             5.6                         5.0             5.4
                                   ---------       ----------                 ----------       ----------
Net income                             7.0%            7.3%                        6.6%            7.0%
                                   ---------       ----------                 ----------       ----------
                                   ---------       ----------                 ----------       ----------
</TABLE>

         NET REVENUE. Net revenue increased $45.6 million, or 60.7%, to
$120.7 million for the three months ended July 4, 1999 from $75.1 million for
the comparable period last year. For the nine months ended July 4, 1999, net
revenue increased $106.3 million, or 53.0%, to $306.9 million from $200.6
million for the comparable period last year. Included in net revenue for the
three months and nine months ended July 4, 1999 was $1.75 million relating to
the over accrual of an allowance for disallowed costs (See Note 5. in Notes
to Condensed Consolidated Financial Statements). This allowance relates to
amounts previously not recognized as revenue as they were deemed to be
unallowable. These amounts were subsequently collected and therefore included
as revenue. Excluding this adjustment, net revenue increased 58.3% and 52.1%
for the three and nine months ended July 4, 1999, respectively. All client
sectors continued to show net revenue increases in actual dollars. As a
percentage of net revenue, decreases were realized in the Federal government
sector due to growth in revenue from commercial clients and revenue
contributed by acquired companies. These acquisitions provided increases in
our revenue from both state and local governments and commercial clients. For
the three months ended July 4, 1999, net revenue provided by companies
acquired in the past 12 months totaled $40.9 million. Excluding this net
revenue, we recognized 6.2% growth in our net revenue. For the nine months
ended July 4, 1999, net revenue

                                      -17-
<PAGE>

provided by companies acquired in the past 12 months totaled $66.7 million.
Excluding this net revenue, we recognized 19.7% growth in our net revenue. Gross
revenue increased $58.9 million, or 59.9%, to $157.1 million for the three
months ended July 4, 1999 from $98.2 million for the comparable period last
year. For the nine months ended July 4, 1999, gross revenue increased $141.8
million, or 55.1%, to $399.1 million from $257.4 million for the comparable
period last year.

         COST OF NET REVENUE. Cost of net revenue increased $33.8 million, or
62.1%, to $88.2 million for the three months ended July 4, 1999 from $54.4
million for the comparable period last year. As a percentage of net revenue,
cost of net revenue for the three months ended July 4, 1999 was 73.0% compared
to 72.4% for the comparable period last year. For the nine months ended July 4,
1999, cost of net revenue increased $83.2 million, or 55.7%, to $232.8 million
from $149.5 million for the comparable period last year. As a percentage of net
revenue, cost of net revenue for the nine months ended July 4, 1999 was 75.8%
compared to 74.5% for the comparable period last year. These increases were
primarily due to the volume increases in our resource management business area,
as well as the higher cost of net revenue for the acquired companies.

         SELLING, GENERAL AND ADMINISTRATIVE EXPENSES. SG&A expenses,
including amortization of intangibles, increased $7.6 million, or 81.6%, to
$17.0 million for the three months ended July 4, 1999 from $9.3 million for
the comparable period last year. As a percent of net revenue, SG&A expenses,
including amortization of intangibles, increased to 14.1% for the three
months ended July 4, 1999 from 12.4% for the comparable period last year. For
the nine months ended July 4, 1999, SG&A expenses, including amortization of
intangibles, increased $12.9 million, or 54.5%, to $36.5 million from $23.6
million for the comparable period last year. As a percentage of net revenue,
SG&A expenses, including amortization of intangibles, increased 11.9% for the
nine months ended July 4, 1999 from 11.8% for the comparable period last
year. Amortization expense relating to acquisitions increased to 1.2% of net
revenue for both the three months and nine months ended July 4, 1999 from
0.9% and 1.0% for the comparable periods last year. As a percentage of net
revenue, the increase in SG&A expenses, including amortization of
intangibles, for the three months ended July 4, 1999 was primarily related to
the timing of expenses associated with upgrading and converting certain
systems to be year 2000 compliant as well as the timing of expenses relating
to further development of our corporate systems and processes. For the nine
months ended July 4, 1999, our SG&A costs, excluding amortization of
intangibles, remained flat at 10.8% of our net revenue.

         NET INTEREST EXPENSE. Net interest expense remained less than $1.0
million for the three months ended July 4, 1999. For the nine months ended July
4, 1999, net interest expense increased $0.6 million, or 51.1%, to $1.8 million
from $1.2 million for the comparable period last year. This increase was
primarily attributable to borrowings on our line of credit to facilitate
acquisitions.

         INCOME TAX EXPENSE. Income tax expense increased $2.3 million, or
55.3%, to $6.5 million for the three months ended July 4, 1999 from $4.2 million
for the comparable period last


                                      -18-
<PAGE>

year. For the nine months ended July 4, 1999, income tax expense increased
$4.7 million, or 43.0%, to $15.5 million from $10.8 million for the
comparable period last year. Certain expenses create permanent differences
that impact our effective tax rate. Our current effective tax rate is 43.2%
compared to 43.5% in fiscal 1998.

LIQUIDITY AND CAPITAL RESOURCES

         As of July 4, 1999, our working capital was $84.0 million, an increase
of $6.9 million from October 4, 1998, of which cash and cash equivalents totaled
$9.3 million. In addition, we have a credit agreement (the "Credit Agreement")
with a bank which provided for a revolving credit facility (the "Facility") of
$65.0 million. Under our Credit Agreement, we may also request standby letters
of credit up to the aggregate sum of $20.0 million outstanding at any given
time. Our Credit Agreement provided for a mandatory reduction of $5.0 million on
December 15, 1999. Our Facility matures on December 15, 2000 or earlier at our
discretion upon payment in full of loans and other obligations. Effective August
2, 1999, we amended the Credit Agreement to provide for a Facility of $80.0
million until February 2000, at which time the Facility will be reduced to $65
million. As of July 4, 1999, borrowings and standby letters of credit totaled
$55.0 million and $1.4 million, respectively.

         In the nine months ended July 4, 1999, we generated $16.8 million
from operating activities compared to our usage of $1.9 million for the
comparable period last year. This increase was primarily attributable to our
efforts to increase our efficiency in the timing of our billings and the
collection of our receivables. Excluding cash used in non-recurring operating
activities of acquired companies of $0.9 million, cash generated from
operating activities would have been $17.5 million. In the nine months ended
July 4, 1999, cash used in investing activities was $41.0 million compared to
$28.3 million for the comparable period last year. This increase primarily
was the result of business acquisitions. In the nine months ended July 4,
1999, cash used in financing activities was $29.2 million compared to cash
generation of $24.8 million for the comparable period last year. During the
nine months ended July 4, 1999, cash generated from operating activities and
the proceeds of our secondary offering allowed us to reduce the outstanding
borrowings on our Facility.

         We expect that internally generated funds, our existing cash balances
and availability under the Credit Agreement, as amended, will be sufficient to
meet our capital requirements through the end of fiscal 1999. However, we may
seek to expand our borrowing capabilities to accommodate acquisition
opportunities.

         We continuously evaluate the marketplace for strategic opportunities.
Once an opportunity is identified, we examine the effect an acquisition may have
on the business environment, as well as on our results of operations. We proceed
with an acquisition if we determine that the acquisition is anticipated to have
an accretive effect on future operations. However, as successful integration and
implementation are essential to achieve favorable results, no assurances can be
given that all acquisitions will provide accretive results. Our strategy is to
position ourselves to address existing and emerging markets. We view
acquisitions as a key component of our growth strategy, and we intend to use
both cash and our securities, as we deem appropriate, to fund such acquisitions.


                                      -19-
<PAGE>

         We believe our operations have not been and, in the foreseeable future,
do not expect to be materially adversely affected by inflation or changing
prices.

MARKET RISKS

         We currently utilize no material derivative financial instruments which
expose us to significant market risk. We are exposed to cash flow risk due to
interest rate fluctuations with respect to our long-term debt. At our option, we
borrow on our Facility (a) at a base rate (the greater of the federal funds rate
plus 0.50% or the bank's reference rate) or (b) at a eurodollar rate plus a
margin which ranges from 0.75% to 1.25%. Borrowings at the base rate have no
designated term and may be repaid without penalty anytime prior to the
Facility's maturity date. Borrowings at a eurodollar rate have a term no less
than 30 days and no greater than 90 days. Typically, at the end of such term,
such borrowings may be rolled over at our discretion upon payment in full of
loans and other obligations. Accordingly, we classify total outstanding debt
between current liabilities and long-term debt based on anticipated payments
within and beyond one year's period of time. We currently anticipate repaying
$21.0 of our outstanding indebtedness under the Facility in the next 12 months.
However there can be no assurance that we will, or will be able to, repay our
long-term debt in the manner described. We could incur additional debt under the
Facility or our operating results could be worse than currently anticipated.

YEAR 2000

         We are working to resolve the potential impact of the year 2000 (Y2K)
on our business operations and the ability of our computerized information
systems to accurately process information that may be date-sensitive. Any of our
programs that recognize a date using "00" as the year 1900 rather than the Y2K
could result in errors or system failures.

         We utilize a number of computer programs across our entire operation.
The primary information technology (IT) systems we utilize are (1) the
accounting and financial systems which include general ledger, accounts payable,
accounts receivable, billing and collection, fixed assets, job cost accounting
and payroll, and (2) human resource information management systems. We do not
believe we have a material amount of non-IT systems upon which we rely.

         We have established both a Y2K review committee and a Y2K action team.
The purpose of the review committee is to develop and communicate our Y2K plan
to achieve our Y2K compliance mission. The purpose of the action team is to
identify, remediate and implement plans to resolve Y2K related issues. Through
the review committee and the action team, we are in the process of completing
our full assessment of all issues relating to the Y2K. We have developed
questionnaires regarding Y2K readiness to be used internally and externally. We
have completed our internal assessment and are assessing the Y2K issues of our
clients and vendors. We rely on certain software vendors who are the makers of
Y2K compliance statements as they apply to our specific software. Our references
to the Y2K compliance status of these systems are republications of their
statements. Based on the information collected to date, we do not believe that
the cost of addressing our Y2K issues will have a material adverse impact on our


                                      -20-
<PAGE>

financial position. We plan to devote all resources required to resolve any
significant Y2K issues in a timely manner.

STATE OF READINESS

         We began our risk assessment in 1995. Since that time we have procured
and implemented certain accounting and financial reporting systems as well as
contract administration and billing systems that have been certified as Y2K
compliant by our vendors. Currently, only one operating unit which accounts for
approximately 4.8% of our gross revenue is not Y2K compliant. We plan to either
convert this unit or upgrade it to a Y2K compliant version of its existing
applications in September 1999. In all cases, we believe that our financial and
accounting systems will be Y2K compliant in a timely manner and will not be
materially impacted by Y2K.

         We have installed a Y2K compliant human resource information management
system. We are currently in the process of converting our non-Y2K compliant
units to this system. The remaining units are deemed to be Y2K compliant by
their vendors, however, they will ultimately be converted to this new system. In
all cases, we believe that our human resource management information systems are
Y2K compliant and will not be materially impacted by Y2K.

         We have expended or obligated approximately $2.6 million on the
procurement of these systems, the conversion of data from legacy systems to
these systems, and on the implementation and testing of these systems.

         We have extensive business with the Federal government. Should the
Federal government, specifically the Department of Defense, experience
significant business interruptions relating to non-Y2K compliance, we could be
materially impacted. To the extent that other third parties upon which we rely,
such as banking institutions, clients and vendors, are unable to address their
Y2K issues in a timely manner, we could be materially impacted. We believe the
worst case scenario relating to Y2K would be an extensive period of time in
which the Federal government and other third parties could not process payments
promptly.

RISKS

         We believe the risks associated with non-Y2K compliance include:

         -  our inability to invoice and process payments;
         -  our inability to produce accurate and timely financials;
         -  the impact on our cash flow and working capital needs;
         -  the impact on our profitability; and
         -  our potential liability to third parties for not meeting contracted
            deliverables.

CONTINGENCY PLANS

         We currently do not have formal contingency plans for the failure of
our financial and accounting systems. We have substantial experience in the
conversion process from multiple


                                      -21-
<PAGE>

legacy systems to our vendor certified Y2K systems. We have an experienced and
dedicated staff to perform the functions identified and are reasonably confident
that the projected conversions will be accomplished as projected.

         We currently do not have formal contingency plans for the failure of
our human resource information management system. Our implementation strategy
was to install the system as simply as possible, with little customization. We
have successfully installed the system and are in the process of loading data
into the system and converting data from legacy systems where possible. We
believe there is sufficient time to complete our conversions in order to meet
the Y2K deadline.

         We maintain, as a matter of policy and practice, mitigation plans in
the event of systems failure, which include regular backup of historical
information. In conjunction with acquisitions, we obtain representations and
warranties from the selling shareholders relating to the Y2K compliance of the
company acquired. For the acquisitions made during the three months ended July
4, 1999, such representations and warranties were obtained.

ITEM 3.  QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK.

         Please refer to the information we have included under the heading
"Market Risks" in ITEM 2. Management's Discussion and Analysis of Financial
Condition and Results of Operations.


                                      -22-

<PAGE>


                                  RISK FACTORS

         SOME OF THE INFORMATION IN THIS QUARTERLY REPORT ON FORM 10-Q CONTAINS
FORWARD-LOOKING STATEMENTS THAT INVOLVE SUBSTANTIAL RISKS AND UNCERTAINTIES. YOU
CAN IDENTIFY THESE STATEMENTS BY FORWARD-LOOKING WORDS SUCH AS "MAY," "WILL,"
"EXPECT," "ANTICIPATE," "BELIEVE," "ESTIMATE" AND "CONTINUE" OR SIMILAR WORDS.
YOU SHOULD READ STATEMENTS THAT CONTAIN THESE WORDS CAREFULLY BECAUSE THEY: (1)
DISCUSS OUR FUTURE EXPECTATIONS; (2) CONTAIN PROJECTIONS OF OUR FUTURE OPERATING
RESULTS OR OF OUR FUTURE FINANCIAL CONDITION; OR (3) STATE OTHER
"FORWARD-LOOKING" INFORMATION. WE BELIEVE IT IS IMPORTANT TO COMMUNICATE OUR
EXPECTATIONS TO OUR INVESTORS. THERE MAY BE EVENTS IN THE FUTURE, HOWEVER, THAT
WE ARE NOT ACCURATELY ABLE TO PREDICT OR OVER WHICH WE HAVE NO CONTROL. THE RISK
FACTORS LISTED IN THIS SECTION, AS WELL AS ANY CAUTIONARY LANGUAGE IN THIS
QUARTERLY REPORT ON FORM 10-Q, PROVIDE EXAMPLES OF RISKS, UNCERTAINTIES AND
EVENTS THAT MAY CAUSE OUR ACTUAL RESULTS TO DIFFER MATERIALLY FROM EXPECTATIONS
DESCRIBED IN FORWARD-LOOKING STATEMENTS. THE OCCURRENCE OF ANY OF THE EVENTS
DESCRIBED IN THESE RISK FACTORS AND ELSEWHERE IN THIS QUARTERLY REPORT ON FORM
10-Q COULD HAVE A MATERIAL ADVERSE EFFECT ON OUR BUSINESS, FINANCIAL CONDITION
AND OPERATING RESULTS. UPON THE OCCURRENCE OF ANY OF THESE EVENTS, THE TRADING
PRICE OF OUR COMMON STOCK COULD DECLINE.

THERE ARE RISKS ASSOCIATED WITH OUR ACQUISITION STRATEGY THAT COULD ADVERSELY
IMPACT OUR BUSINESS AND OPERATING RESULTS

         A significant part of our growth strategy is to acquire other companies
that complement our lines of business or that broaden our geographic presence.
During fiscal 1998, we purchased ten companies in five separate transactions.
During the nine months ended July 4, 1999, we purchased seven companies. We
expect to continue to acquire companies as an element of our growth strategy.
Acquisitions involve certain risks that could cause our actual growth or
operating results to differ from our expectations or the expectations of
security analysts. For example:

          -    We may not be able to identify suitable acquisition candidates or
               to acquire additional companies on favorable terms;
          -    We compete with others to acquire companies. Competition may
               increase and may result in decreased availability or increased
               price for suitable acquisition candidates;
          -    We may not be able to obtain the necessary financing, on
               favorable terms or at all, to finance any potential acquisitions;
          -    We may ultimately fail to consummate an acquisition even if
               announced that we plan to acquire a company;
          -    We may fail to successfully integrate or manage these acquired
               companies due to differences in business backgrounds or corporate
               cultures;
          -    These acquired companies may not perform as we expect;
          -    We may find it difficult to provide a consistent quality of
               service across our geographically diverse operations; and
          -    If we fail to successfully integrate any acquired company, our
               reputation could be damaged. This could make it more difficult to
               market our services or to acquire additional companies in the
               future.

                                      -23-
<PAGE>

In addition, our acquisition strategy may divert management's attention away
from our primary service offerings, result in the loss of key clients or
personnel and expose us to unanticipated liabilities.

         Finally, acquired companies that derive a significant portion of their
revenues from the Federal government and that do not follow the same cost
accounting policies and billing procedures as we do may be subject to larger
cost disallowances for greater periods than we typically encounter. If we fail
to determine the existence of unallowable costs and establish appropriate
reserves in advance of an acquisition we may be exposed to material
unanticipated liabilities, which could have a material adverse effect on our
business.

OUR QUARTERLY OPERATING RESULTS MAY FLUCTUATE SIGNIFICANTLY, WHICH COULD HAVE A
NEGATIVE EFFECT ON THE PRICE OF OUR COMMON STOCK

         Our quarterly revenues, expenses and operating results may fluctuate
significantly because of a number of factors, including:

          -    The seasonality of the spending cycle of public sector clients,
               notably the Federal government;
          -    Employee hiring and utilization rates;
          -    The number and significance of client engagements commenced and
               completed during a quarter;
          -    Delays incurred in connection with an engagement;
          -    The ability of clients to terminate engagements without
               penalties;
          -    The size and scope of engagements;
          -    The timing of expenses incurred for corporate initiatives;
          -    The timing and size of the return on investment capital; and
          -    General economic and political conditions.

Variations in any of these factors could cause significant fluctuations in our
operating results from quarter to quarter and could result in net losses.

THE VALUE OF OUR COMMON STOCK COULD CONTINUE TO BE VOLATILE

         The trading price of our common stock has fluctuated widely. In
addition, in recent years the stock market has experienced extreme price and
volume fluctuations. The overall market and the price of our common stock may
continue to fluctuate greatly. The trading price of our common stock may be
significantly affected by various factors, including:

          -    Quarter to quarter variations in our operating results;
          -    Changes in environmental legislation;
          -    Changes in investors' and analysts' perception of the business
               risks and conditions of our business;
          -    Broader market fluctuations; and
          -    General economic or political conditions.


                                      -24-
<PAGE>

IF WE ARE NOT ABLE TO SUCCESSFULLY MANAGE OUR GROWTH STRATEGY, OUR BUSINESS AND
RESULTS OF OPERATIONS MAY BE ADVERSELY AFFECTED

         We are growing rapidly. Our growth presents numerous managerial,
administrative, operational and other challenges. Our ability to manage the
growth of our operations will require us to continue to improve our operational,
financial and human resource management information systems and our other
internal systems and controls. In addition, our growth will increase our need to
attract, develop, motivate and retain both our management and professional
employees. The inability of our management to manage our growth effectively or
the inability of our employees to achieve anticipated performance or utilization
levels, could have a material adverse effect on our business.

THE LOSS OF KEY PERSONNEL OR OUR INABILITY TO ATTRACT AND RETAIN QUALIFIED
PERSONNEL COULD SIGNIFICANTLY DISRUPT OUR BUSINESS

         We depend upon the efforts and skills of our executive officers, senior
managers and consultants. With limited exceptions, we do not have employment
agreements with any of these individuals. The loss of the services of any of
these key personnel could adversely affect our business. Although we have
obtained non-compete agreements from certain principals and stockholders of
companies we have acquired, we generally do not have non-compete or employment
agreements with key employees who were not once equity shareholders of these
companies. We do not maintain key-man life insurance policies on any of our
executive officers or senior managers.

         Our future growth and success depends on our ability to attract and
retain qualified scientists and engineers. The market for these professionals is
competitive and we may not be able to attract and retain such professionals.

CHANGES IN EXISTING LAWS AND REGULATIONS COULD REDUCE THE DEMAND FOR OUR
SERVICES

         A significant amount of our resource management business is generated
either directly or indirectly as a result of existing Federal and state
governmental laws, regulations and programs. Any changes in these laws or
regulations that reduce funding or affect the sponsorship of these programs
could reduce the demand for our services and could have a material adverse
effect on our business.

OUR REVENUES FROM AGENCIES OF THE FEDERAL GOVERNMENT ARE CONCENTRATED, AND A
REDUCTION IN SPENDING BY THESE AGENCIES COULD ADVERSELY AFFECT OUR BUSINESS AND
OPERATING RESULTS

         Agencies of the Federal government are among our most significant
clients. During the nine months ended July 4, 1999, approximately 39.6% of our
net revenue was derived from Federal agencies, of which 22.2% was derived from
the Department of Defense (DOD), 12.5% from the Environmental Protection Agency
(EPA), 2.9% from the Department of Energy (DOE), and 2.0% from various other
Federal government agencies. Some contracts with Federal government agencies
require annual funding approval and may be terminated at their discretion. A
reduction in spending by Federal government agencies could limit the continued
funding of


                                      -25-
<PAGE>

existing contracts with them and could limit our ability to obtain additional
contracts. These limitations, if significant, could have a material adverse
effect on our business.

         Additionally, the failure of clients to pay significant amounts due us
for our services could adversely affect our business. For example, we recently
received notification from a Federal government agency that we are entitled to
payments in excess of our billings. However, the agency involved must obtain
specific funding approval for amounts owed to us and there can be no assurance
this funding approval will be obtained.

OUR CONTRACTS WITH GOVERNMENTAL AGENCIES ARE SUBJECT TO AUDIT, WHICH COULD
RESULT IN THE DISALLOWANCE OF CERTAIN COSTS

         Contracts with the Federal government and other governmental agencies
are subject to audit. Most of these audits are conducted by the Defense Contract
Audit Agency (DCAA), which reviews our overhead rates, operating systems and
cost proposals. The DCAA may disallow costs if it determines that we accounted
for these costs incorrectly or in a manner inconsistent with Cost Accounting
Standards. A disallowance of costs by the DCAA, or other governmental auditors,
could have a material adverse effect on our business.

         In September 1995, we acquired PRC Environmental Management, Inc.
(EMI). EMI also contracts with Federal government agencies and such contracts
are also subject to the same governmental audits. At the time of acquisition,
audits had not yet been completed or finalized. Accordingly, reserves were
established for potential disallowances. Since then, the DCAA has completed
audits of EMI's contracts for the fiscal years 1987 through 1995. As a result of
these audits and negotiations with the DCAA, the DCAA disallowed approximately
$4.4 million in costs which have been applied against the established reserves.

OUR BUSINESS AND OPERATING RESULTS COULD BE ADVERSELY AFFECTED BY LOSSES UNDER
FIXED-PRICE CONTRACTS OR TERMINATION OF CONTRACT AT THE CLIENT'S DISCRETION

         We contract with Federal and state governments as well as with the
commercial sector. These contracts are often subject to termination at the
discretion of the client with or without cause. Additionally, we enter into
various types of contracts with our clients, including fixed-price contracts.
Fixed-price contracts protect clients and expose us to a number of risks.
These risks include underestimation of costs, problems with new technologies,
unforeseen costs or difficulties, delays beyond our control and economic and
other changes that may occur during the contract period. Losses under
fixed-price contracts or termination of contracts at the discretion of the
client could have a material adverse effect on our business.

         In fiscal 1999, we had a contract change with Tele-Communications,
Inc. involving three turnkey contracts. This change was due in part to
Tele-Communications, Inc.'s change in strategy from the use of turnkey
contracts to the use of direct service contracts in the upgrading of its
network systems.

OUR INABILITY TO FIND QUALIFIED SUBCONTRACTORS COULD ADVERSELY AFFECT THE
QUALITY OF OUR SERVICE AND OUR ABILITY TO PERFORM UNDER CERTAIN CONTRACTS


                                      -26-
<PAGE>

         Under some of our contracts, we depend on the efforts and skills of
subcontractors for the performance of certain tasks. Reliance on subcontractors
varies from project to project. In the nine months ended July 4, 1999,
subcontractor costs comprised 23.1% of our gross revenue. The absence of
qualified subcontractors with whom we have a satisfactory relationship could
adversely affect the quality of our service and our ability to perform under
some of our contracts.

OUR INDUSTRY IS HIGHLY COMPETITIVE AND WE MAY BE UNABLE TO COMPETE EFFECTIVELY

         We provide specialized management consulting and technical services to
a broad range of public and private sector clients. The market for our services
is highly competitive and we compete with many other firms. These firms range
from small regional firms to large national firms which may have greater
financial and marketing resources than ours.

         We focus primarily on the resource management, infrastructure and
communications business areas. We provide services to our clients which include
Federal, state and local agencies, and organizations in the private sector.

         We compete for projects and engagements with a number of competitors
which can vary from 10 to 100 firms. Historically, clients have chosen among
competing firms based on the quality and timeliness of the firm's service. We
believe, however, that price has become an increasingly important factor.

         We believe that our principal competitors include, in alphabetical
order, Black & Veatch LLP; Brown & Caldwell; Castle Tower Corporation; Camp,
Dresser & McKee; CH2M Hill Companies Ltd.; Dames & Moore Group; EA Engineering,
Science & Technology, Inc.; Earth Tech, Inc.; ICF Kaiser International, Inc.; IT
Group Inc.; Mastec, Inc.; Montgomery Watson; OSP Consultants, Inc.; Roy F.
Weston, Inc.; and URS Greiner Corporation.

OUR SERVICES EXPOSE US TO SIGNIFICANT RISKS OF LIABILITY AND OUR INSURANCE
POLICIES MAY NOT PROVIDE ADEQUATE COVERAGE

         Our services involve significant risks of professional and other
liabilities which may substantially exceed the fees we derive from our services.
Our business activities could expose us to potential liability under various
environmental laws such as the Comprehensive Environmental Response,
Compensation and Liability Act of 1980 (CERCLA). In addition, we sometimes
contractually assume liability under indemnification agreements. We cannot
predict the magnitude of such potential liabilities.

         We currently maintain comprehensive general liability, umbrella and
professional liability insurance policies. We believe that our insurance
policies are adequate for our business operations. Professional liability
policies are "claims made" policies; thus, only claims made during the term of
the policy are covered. Should we terminate our professional liability policy
and not obtain retroactive coverage, we would be uninsured for claims made after
termination even if these claims are based on events or acts that occurred
during the term of the policy. Additionally, our insurance policies may not
protect us against potential liability due to various exclusions and retentions.
Should we expand into new markets, we may not be able to obtain


                                      -27-
<PAGE>

insurance coverage for such activities or, if insurance is obtained, the dollar
amount of any liabilities incurred could exceed our insurance coverage.
Partially or completely uninsured claims, if successful and of significant
magnitude, could have a material adverse affect on our business.

WE MAY BE PRECLUDED FROM PROVIDING CERTAIN SERVICES DUE TO CONFLICT OF INTEREST
ISSUES

         Many of our clients are concerned about potential or actual conflicts
of interest in retaining management consultants. Federal government agencies
have formal policies against continuing or awarding contracts that would create
actual or potential conflicts of interest with other activities of a contractor.
These policies, among other things, may prevent us from bidding for or
performing contracts resulting from or relating to certain work we have
performed for the government. In addition, services performed for a private
client may create a conflict of interest that precludes or limits our ability to
obtain work from other public or private organizations. We have, on occasion,
declined to bid on projects because of these conflicts of interest issues.

OUR INTERNATIONAL OPERATIONS EXPOSE US TO RISKS SUCH AS FOREIGN CURRENCY
FLUCTUATIONS

         In the nine months ended July 4, 1999, approximately 3.8% of our net
revenue was derived from the international marketplace. Some contracts with our
international clients are denominated in foreign currencies. As such, these
contracts contain inherent risks including foreign currency exchange risk and
the risk associated with expatriating funds from foreign countries. If our
international revenue increases, our exposure to foreign currency fluctuations
will also increase. We have entered into forward exchange contracts to address
foreign currency fluctuations.

WE COULD EXPERIENCE BUSINESS INTERRUPTIONS RELATING TO THE YEAR 2000

         We are working to resolve the potential impact of the year 2000 (Y2K)
on its business operations and the ability of its computerized information
systems to accurately process information that may be date-sensitive. Any of its
programs that recognize a date using "00" as the year 1900 rather than the Y2K
could result in errors or system failures.

         We utilize a number of computer programs across our entire operation.
The primary information technology systems we utilize are the accounting and
financial and human resource information management systems. We began our risk
assessment in 1995. Since that time we have procured and implemented certain
accounting and financial reporting systems as well as contract administration
and billing systems that have been certified as Y2K compliant by our vendors.
Currently, only one of our operating units which accounts for approximately 4.8%
of our gross revenue is not Y2K compliant. We plan to either convert this unit
or upgrade it to a Y2K compliant version of its existing applications in
September 1999. In all cases, we believe that our financial and accounting
systems will be Y2K compliant in a timely manner and will not be materially
impacted by Y2K.

         We have extensive business with the Federal government. Should the
Federal government, especially the Department of Defense, experience significant
business interruptions




                                      -28-
<PAGE>

relating to non-Y2K compliance, we could be materially impacted. To the extent
that other third parties upon which we rely, such as banking institutions,
clients and vendors, are unable to address their Y2K issues in a timely manner,
we could be materially impacted. We believe that the worst case scenario
relating to Y2K would be an extensive period of time in which the Federal
government and other third parties could not process payments promptly, in
addition to the Company's financial institutions not being able to supply the
Company with its working capital needs.

         Additional risks associated with non-Y2K compliance include:

          -    our inability to invoice and process payments;
          -    our inability to produce accurate and timely financials;
          -    the impact on our cash flow and working capital needs;
          -    the impact on our profitability; and
          -    our potential liability to third parties for not meeting
               contracted deliverables.


                                      -29-
<PAGE>

                           PART II. OTHER INFORMATION

ITEM 2.    CHANGES IN SECURITIES AND USE OF PROCEEDS.

           On May 7, 1999, we acquired 100.0% of the capital stock of
Collins/Pina Consulting Engineers, Inc., an Arizona corporation (CPC), through
stock purchases from the former shareholders of CPC (the "Stock Purchase"). In
connection with the Stock Purchase, we issued an aggregate of 6,172 shares of
our Common Stock, $.01 par value ("Common Stock"), to one of the former
shareholders of CPC. For purposes of the Stock Purchase, each share of Common
Stock was valued at $19.44. The issuance of Common Stock was made by private
placement in reliance on the exemption from the registration provisions of the
Securities Act of 1933, as amended (the "Act"), provided for in Section 4(2) of
the Act.

           On May 21, 1999, we acquired 100.0% of the capital stock of BAHA
Communications, Inc., a Nevada corporation (BCI), through a merger of a
wholly-owned subsidiary with and into BCI (the "BCI Merger"). In connection with
the BCI Merger, we issued an aggregate of 176,168 shares of our Common Stock to
the former shareholders of BCI. For purposes of the BCI Merger, each share of
Common Stock was valued at $17.08. The issuances of Common Stock were made by
private placement in reliance on the exemption from the registration provisions
of the Act, provided for in Section 4(2) of the Act.

           On June 18, 1999, we acquired 100.0% of the capital stock of
Utilities & C.C., Inc., a California corporation (UCC), through a merger of a
wholly-owned subsidiary with and into UCC (the "UCC Merger"). In connection
with the UCC Merger, we issued an aggregate of 137,930 shares of our Common
Stock to the former shareholders of UCC. For purposes of the UCC Merger, each
share of Common Stock was valued at $17.40. The issuance of Common Stock was
made by private placement in reliance on the exemption from the registration
provisions of the Act, provided for in Section 4(2) of the Act.

ITEM 6.    EXHIBITS AND REPORTS ON FORM 8-K.

(a)        EXHIBITS

                 3.1             Restated Certificate of Incorporation of the
                                 Company (incorporated herein by reference to
                                 Exhibit 3.1 to the Company's Annual Report on
                                 Form 10-K for the fiscal year ended October 1,
                                 1995).

                 3.2             Bylaws of the Company as amended to date
                                 (incorporated herein by reference to Exhibit
                                 3.2 to the Company's Registration Statement on
                                 Form S-1, No. 33-43723).

                 3.3             Certificate of Amendment of Certificate of
                                 Incorporation of the Company (incorporated
                                 herein by reference to Exhibit 3.4 to the
                                 Company's Annual Report on Form 10-K for the
                                 fiscal year ended October 4, 1998).


                                      -30-
<PAGE>

                 10.1            Credit Agreement dated as of September 15, 1995
                                 between the Company and Bank of America
                                 Illinois, as amended by the First Amendment to
                                 Credit Agreement dated as of November 27, 1995
                                 (incorporated herein by reference to Exhibit
                                 10.1 to the Company's Annual Report on Form
                                 10-K for the fiscal year ended October 1,
                                 1995).

                 10.2            Second Amendment dated as of June 20, 1997 to
                                 the Credit Agreement dated as of September 15,
                                 1995 between the Company and Bank of America
                                 Illinois (incorporated herein by reference to
                                 Exhibit 10.2 to the Company's Quarterly Report
                                 on Form 10-Q for the fiscal quarter ended June
                                 29, 1997).

                 10.3            Third Amendment dated as of December 15, 1997
                                 to the Credit Agreement dated as of September
                                 15, 1995 between the Company and Bank of
                                 America National Trust and Savings Association
                                 (incorporated herein by reference to Exhibit
                                 10.3 to the Company's Annual Report on Form
                                 10-K for the fiscal year ended September 28,
                                 1997).

                 10.4            Fourth Amendment dated as of January 30, 1997
                                 to the Credit Agreement dated as of September
                                 15, 1995 between the Company and Bank of
                                 America National Trust and Savings Association
                                 (incorporated herein by reference to Exhibit
                                 10.4 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended December 28,
                                 1997).

                 10.5            Fifth Amendment dated as of July 6, 1998 to the
                                 Credit Agreement dated as of September 15, 1995
                                 between the Company and Bank of America
                                 National Trust and Savings Association
                                 (incorporated herein by reference to Exhibit
                                 10.4 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended).

                 10.6            Sixth Amendment dated as of July 21, 1999 to
                                 the Credit Agreement dated as of September 15,
                                 1995 between the Company and Bank of America
                                 National Trust and Savings Association.

                 10.7            Security Agreement dated as of September 15,
                                 1995 among the Company, GeoTrans, Inc., Simons
                                 Li & Associates, Inc., Hydro-Search, Inc., PRC
                                 Environmental Management, Inc. and Bank of
                                 America Illinois (incorporated herein by
                                 reference to Exhibit 10.2 to the Company's
                                 Annual Report on Form 10-K for the fiscal year
                                 ended October 1, 1995).


                                      -31-
<PAGE>

                 10.8            Pledge Agreement dated as of September 15, 1995
                                 between the Company and Bank of America
                                 Illinois (incorporated herein by reference to
                                 Exhibit 10.3 to the Company's Annual Report on
                                 Form 10-K for the fiscal year ended October 1,
                                 1995).

                 10.9            Guaranty dated as of September 15, 1995,
                                 executed by the Company in favor of Bank of
                                 America Illinois (incorporated herein by
                                 reference to Exhibit 10.4 to the Company's
                                 Annual Report on Form 10-K for the fiscal year
                                 ended October 1, 1995).

                 10.10           1989 Stock Option Plan dated as of February 1,
                                 1989 (incorporated herein by reference to
                                 Exhibit 10.13 to the Company's Registration
                                 Statement on Form S-1, No. 33-43723).

                 10.11           Form of Incentive Stock Option Agreement
                                 executed by the Company and certain individuals
                                 in connection with the Company's 1989 Stock
                                 Option Plan (incorporated herein by reference
                                 to Exhibit 10.14 to the Company's Registration
                                 Statement on Form S-1, No. 33-43723).

                 10.12           Executive Medical Reimbursement Plan
                                 (incorporated herein by reference to Exhibit
                                 10.16 to the Company's Registration Statement
                                 on Form S-1, No. 33-43723).

                 10.13           1992 Incentive Stock Plan (incorporated herein
                                 by reference to Exhibit 10.18 to the Company's
                                 Annual Report on Form 10-K for the fiscal year
                                 ended October 3, 1993).

                 10.14           Form of Incentive Stock Option Agreement used
                                 by the Company in connection with the Company's
                                 1992 Incentive Stock Plan (incorporated herein
                                 by reference to Exhibit 10.19 to the Company's
                                 Annual Report on Form 10-K for the fiscal year
                                 ended October 3, 1993).

                 10.15           1992 Stock Option Plan for Nonemployee
                                 Directors (incorporated herein by reference to
                                 Exhibit 10.20 to the Company's Annual Report on
                                 Form 10-K for the fiscal year ended October 3,
                                 1993).

                 10.16           Form of Nonqualified Stock Option Agreement
                                 used by the Company in connection with the
                                 Company's 1992 Stock Option Plan for
                                 Nonemployee Directors (incorporated herein by
                                 reference to Exhibit 10.21 to the Company's
                                 Annual Report on Form 10-K for the fiscal year
                                 ended October 3, 1993).


                                      -32-
<PAGE>

                 10.17           1994 Employee Stock Purchase Plan (incorporated
                                 herein by reference to Exhibit 10.22 to the
                                 Company's Annual Report on Form 10-K for the
                                 fiscal year ended October 2, 1994).

                 10.18           Form of Stock Purchase Agreement used by the
                                 Company in connection with the Company's 1994
                                 Employee Stock Purchase Plan (incorporated
                                 herein by reference to Exhibit 10.23 to the
                                 Company's Annual Report on Form 10-K for the
                                 fiscal year ended October 2, 1994).

                 10.19           Employment Agreement dated as of June 11, 1997
                                 between the Company and Daniel A. Whalen
                                 (incorporated herein by reference to Exhibit
                                 10.16 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended June 29,
                                 1997).

                 10.20           Registration Rights Agreement dated as of June
                                 11, 1997 among the Company and the parties
                                 listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.17 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended June 29,
                                 1997).

                 10.21           Registration Rights Agreement dated as of July
                                 11, 1997 among the Company and the parties
                                 listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.18 to the Company's Annual Report on Form
                                 10-K for the fiscal year ended September 28,
                                 1997).

                 10.22           Registration Rights Agreement dated as of March
                                 26, 1998 among the Company and the parties
                                 listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.20 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended March 29,
                                 1998).

                 10.23           Registration Rights Agreement dated as of July
                                 9, 1998 among the Company and the parties
                                 listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.22 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended June 28,
                                 1998).

                 10.24           Registration Rights Agreement dated as of
                                 September 22, 1998 among the Company and the
                                 parties listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.23 to the Company's Annual Report on Form
                                 10-K for the fiscal year ended October 4,
                                 1998).


                                      -33-
<PAGE>

                 10.25           Registration Rights Agreement dated as of
                                 February 26, 1999 among the Company and the
                                 parties listed on Schedule A attached thereto
                                 (incorporated herein by reference to Exhibit
                                 10.24 to the Company's Quarterly Report on Form
                                 10-Q for the fiscal quarter ended April 4,
                                 1999).

                 10.26           Registration Rights Agreement dated as of May
                                 7, 1999 among the Company and the parties
                                 listed on Schedule A attached thereto.

                 10.27           Registration Rights Agreement dated as of May
                                 21, 1999 among the Company and the parties
                                 listed on Schedule A attached thereto.

                 10.28           Registration Rights Agreement dated as of June
                                 18, 1999 among the Company and the parties
                                 listed on Schedule A attached thereto.

                 11              Computation of Net Income Per Common Share.

                 27              Financial Data Schedule.


(b)        REPORTS ON FORM 8-K

           None


                                      -34-
<PAGE>

                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


         Dated:  August 18, 1999             TETRA TECH, INC.



                                By: /s/ Li-San Hwang
                                    ----------------------------------------
                                    Li-San Hwang
                                    Chairman of the Board of Directors,
                                    President and Chief Executive Officer
                                    (Principal Executive Officer)



                                By: /s/ James M. Jaska
                                    ----------------------------------------
                                    James M. Jaska
                                    Vice President, Chief Financial Officer and
                                    Treasurer
                                    (Principal Financial and Accounting Officer)



                                      -35-

<PAGE>

                                                                  EXHIBIT 10.6

                                 SIXTH AMENDMENT

     THIS SIXTH AMENDMENT (this "Sixth Amendment") dated as of July 21, 1999
is to the Credit Agreement (the "Credit Agreement") dated as of September 15,
1995 between TETRA TECH, INC. (the "Company") and BANK OF AMERICA NATIONAL
TRUST AND SAVINGS ASSOCIATION (the "Bank").  Unless otherwise defined herein,
terms defined in the Credit Agreement are used herein as defined therein.

     WHEREAS, the parties hereto have entered into the Credit Agreement which
provides for the Bank to make Loans to, and to issue Letters of Credit for
the account of, the Company from time to time; and

     WHEREAS, the parties hereto desire to amend the Credit Agreement as set
forth below;

     NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration (the receipt and sufficiency of which are hereby
acknowledged), the parties hereto agree as follows:

     SECTION 1  AMENDMENTS.  Effective on (and subject to the occurrence of)
the Sixth Amendment Effective Date (as defined below), the Credit Agreement
shall be amended as follows:

     SECTION 1.1 Section 2.1.  Section 2.1 of the Credit Agreement is amended
by deleting the amount "$70,000,000" therein and substituting the amount
"$85,000,000" therefor.

     SECTION 1.2 Section 6.1.1.  Section 6.1.1 of the Credit Agreement is
amended in its entirety to read as follows:

          6.1.1 Scheduled Reductions of Commitment.  The amount of the
     commitment shall be permanently reduced by $25,000,000 on February 1,
     2000.

     SECTION 1.3  Exhibit A.  Exhibit A to the Credit Agreement is hereby
amended in its entirety to read in the form of  Exhibit A hereto.

     SECTION 2  REPRESENTATIONS AND WARRANTIES.  The Company represents and
warrants to the Bank that (a) each warranty set forth in Section 9 of the
Credit Agreement is true and correct as if made on the date hereof, (b) the
execution and delivery by the Company of this Sixth Amendment and the New
Note (as defined below), and the performance by the Company of its
obligations under the Credit Agreement as amended hereby (as so amended, the
"Amended Credit Agreement") and the New Note (i) are within the corporate



<PAGE>

powers of the Company and each Subsidiary, (ii) have been duly authorized by
all necessary corporate action, (iii) have received all necessary
governmental approval and (iv) do not and will not contravene or conflict
with any provision of law or of the charter or by-laws of the Company or any
Subsidiary or of any indenture, loan agreement or other material contract,
order or decree which is binding upon the Company or any Subsidiary, and (c)
this Sixth Amendment, the Amended Credit Agreement, and the New Note are the
legal, valid and binding obligations of the Company and each Subsidiary which
is party hereto, enforceable against the Company and each Subsidiary in
accordance with their terms, except as enforceability may be limited by
bankruptcy, insolvency or other similar laws of general application affecting
the enforcement of creditor's rights or by general principles of equity
limiting the availability of equitable remedies.

     SECTION 3  EFFECTIVENESS.  The amendments set forth in Section 1 shall
become effective, as of the day and year first above written, on such date
(the "Sixth Amendment Effective Date") that the Bank shall have received (i)
an amendment fee of $25,000, (ii) counterparts of this Sixth Amendment
executed by the parties hereto and (iii) each of the following documents in
form and substance satisfactory to the Bank:

     (a)  Resolutions of Company.  Certified copies of resolutions of the
Board of Directors of the Company authorizing the execution and delivery of
this Sixth Amendment and the performance of its obligations under the Amended
Credit Agreement.

     (b)  Incumbency and Signature Certificate of Company.  A certificate of
the Secretary or the Assistant Secretary of the Company certifying the names
and true signatures of the officers of the Company authorized to execute,
deliver and perform, as applicable, this Sixth Amendment and all other
documents to be executed in connection therewith.

     (c) New Note.  A promissory note of the Company (the "New Note") in the
form of Exhibit A hereto.

     (d) Opinion.  The opinion of Riordan & McKinzie, counsel to the Company
and its Subsidiaries, in form and substance satisfactory to the Bank

     SECTION 4  MISCELLANEOUS.

     SECTION 4.1  Continuing Effectiveness, etc.  As herein amended, the
Credit Agreement shall remain in full force and effect and is hereby ratified
and confirmed in all respects.

     SECTION 4.2  Counterparts.  This Sixth Amendment may be executed in any
number of counterparts and by the different parties on separate counterparts,
and each such counterpart shall be deemed to be an original but all such
counterparts shall together constitute one and the same Sixth Amendment.

                                     -2-


<PAGE>

     SECTION 4.3  Governing Law.  This Sixth Amendment shall be a contract
made under and governed by the laws of the State of Illinois applicable to
contracts made and to be performed entirely within such State.

     SECTION 4.4  Successors and Assigns.  This Sixth Amendment shall be
binding upon the Company and the Bank and their respective successors and
assigns, and shall inure to the benefit of the Company and the Bank and the
successors and assigns of the Bank.




                                     -3-


<PAGE>

     Delivered at Chicago, Illinois, as of the day and year first above
written.

                                           TETRA TECH, INC.

                                           By: /s/ James M. Jaska
                                              ------------------------------
                                           Title: Chief Financial Officer
                                                 ---------------------------


                                           BANK OF AMERICA NATIONAL TRUST AND
                                           SAVINGS ASSOCIATION

                                           By: /s/ Timothy J. Pepowski
                                               ------------------------------
                                           Title: S.V.P.
                                                  ---------------------------



<PAGE>

Each of the undersigned hereby acknowledges and agrees to the foregoing Sixth
Amendment and the Amended Credit Agreement and hereby confirms the continuing
effectiveness of the Guaranty and the Security Agreement with respect to the
Amended Credit Agreement.

                                           HSI GEOTRANS, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Assistant Treasurer
                                                  --------------------------


                                           SIMONS, LI & ASSOCIATES, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Assistant Treasurer
                                                  --------------------------


                                           TETRA TECH EM, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           WHALEN & COMPANY, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Chief Financial Officer
                                                  --------------------------


                                           TETRA TECH NUS, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


<PAGE>


                                           MFG, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           COLLINS-PINA CONSULTING
                                             ENGINEERS, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           DEA CONSTRUCTION COMPANY, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           BAHA COMMUNICATIONS, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           UTILITIES & C.C., INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           ASL CONSULTING ENGINEERS, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


                                           COSENTINI ASSOCIATES, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Treasurer
                                                  --------------------------


<PAGE>

                                   EXHIBIT A

                                 FORM OF NOTE


$85,000,000                                                       July 21, 1999
Chicago, Illinois

     The undersigned, for value received, promises to pay to the order of
BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION, a national banking
association having an office at 231 South LaSalle Street, Chicago, Illinois
(the "Bank") at the principal office of the Bank in Chicago, Illinois,
EIGHTY-FIVE MILLION DOLLARS or, if less, the aggregate unpaid amount of all
Loans made by the undersigned pursuant to the Credit Agreement referred to
below (as shown on the schedule attached hereto (and any continuation
thereof) or in the records of the Bank), such principal amount to be payable
in installments as set forth in the Credit Agreement.

     The undersigned further promises to pay interest on the unpaid principal
amount of each Loan from the date of such Loan until such Loan is paid in
full, payable at the rate(s) and at the time(s) set forth in the Credit
Agreement.  Payments of both principal and interest are to be made in lawful
money of the United States of America.

     This Note evidences indebtedness incurred under, and is subject to the
terms and provisions of, the Credit Agreement, dated as of September 15, 1995
(as amended or otherwise modified from time to time, the "Credit Agreement";
terms not otherwise defined herein are used herein as defined in the Credit
Agreement), between the undersigned and the Bank, to which Credit Agreement
reference is hereby made for a statement of the terms and provisions under
which this Note may or must be paid prior to its due date or its due date
accelerated.

     In addition to and not in limitation of the foregoing and the provisions
of the Credit Agreement, the undersigned further agrees, subject only to any
limitation imposed by applicable law, to pay all expenses, including
reasonable attorneys' fees and legal expenses, incurred by the holder of this
Note in endeavoring to collect any amounts payable hereunder which are not
paid when due, whether by acceleration or otherwise.


                                     -7-


<PAGE>

     This Note is made under and governed by the laws of the State of
Illinois applicable to contracts made and to be performed entirely within
such State.

                                           TETRA TECH, INC.

                                           By: /s/ James M. Jaska
                                               -----------------------------
                                           Title: Chief Financial Officer
                                                  --------------------------





                                     -8-


<PAGE>

Schedule Attached to Note dated July 21, 1999 of TETRA TECH, INC. payable to
the order of BANK OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION.


Date and           Date and
Amount of          Amount of
Loan or of         Repayment or of    Interest
Conversion from    Conversion into    Period/     Unpaid
another type of    another type of    Maturity    Principal   Notation
Loan               Loan               Date        Balance     Made by


                         1.  FLOATING RATE LOANS

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________


                           2.  EURODOLLAR LOANS

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________


                                     -9-


<PAGE>

                                                                 EXHIBIT 10.26


                          REGISTRATION RIGHTS AGREEMENT

     This Registration Rights Agreement (the "Agreement") is entered into as
of May 7, 1999 by and among Tetra Tech, Inc., a Delaware corporation ("Tetra
Tech"), and the parties listed on SCHEDULE A attached hereto (each, a
"Holder" and collectively, the "Holders").


                                 R E C I T A L S

     A.   Tetra Tech and the Holders are parties to Stock Purchase Agreement
dated April 30, 1999 (the "Stock Purchase Agreement"), pursuant to which Tetra
Tech will acquire all of the outstanding shares of capital stock of Collins/Pina
Consulting Engineers, Inc., an Arizona corporation ("C/P").

     B.   Pursuant to the Stock Purchase Agreement, the shareholders of C/P will
receive shares of the common stock, $.01 par value, of Tetra Tech ("Tetra Tech
Common Stock"); and

     C.   This Agreement is the Registration Rights Agreement referred to in
SECTION 7.10 of the Stock Purchase Agreement and, pursuant thereto, must be
entered into by the parties in connection with the consummation of the
transactions contemplated by the Stock Purchase Agreement.


                                A G R E E M E N T

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

     1.   CERTAIN DEFINITIONS.  As used in this Agreement, the following terms
shall have the following respective meanings:

          "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934,
as amended from time to time.


<PAGE>

          "FORM S-3" shall mean such form under the Securities Act as in effect
on the date hereof or any successor registration form under the Securities Act
subsequently adopted by the SEC which permits inclusion or incorporation of
substantial information by reference to other documents filed by Tetra Tech with
the SEC.

          "PROSPECTUS" shall mean the prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement, with respect
to the terms of the offering of any portion of the Registrable Securities
covered by the Registration Statement and by all other amendments and
supplements to the prospectus, including post-effective amendments and all
material incorporated by reference in such Prospectus.

          "REGISTER", "REGISTERED" and "REGISTRATION" shall mean and refer to a
registration effected by preparing and filing a Registration Statement and
taking all other actions that are necessary or appropriate in connection
therewith, and the declaration or ordering of effectiveness of such Registration
Statement by the SEC.

          "REGISTRATION EXPENSES" shall have the meaning set forth in SECTION 4.

          "REGISTRABLE SECURITIES" shall mean the shares of Tetra Tech Common
Stock (i) issued pursuant to the Stock Purchase Agreement, and (ii) issued as a
dividend or other distribution with respect to or in exchange for or in
replacement of the shares referenced in (i) above; PROVIDED, HOWEVER, that
Registrable Securities shall not include any shares of Tetra Tech Common Stock
that have previously been registered or sold to the public or have been sold
pursuant to Rule 144 (or similar successor Rule).

          "REGISTRATION STATEMENT" shall mean any registration statement of
Tetra Tech in compliance with the Securities Act that covers Registrable
Securities pursuant to the provisions of this Agreement, including, without
limitation, the Prospectus, all amendments and supplements to such Registration
Statement, including all post-effective amendments, all exhibits and all
material incorporated by reference in such Registration Statement.

          "RULE 144" shall mean Rule 144 promulgated under the Securities Act or
any similar successor rule, as the same shall be in effect from time to time.

          "RULE 144A" shall mean Rule 144A promulgated under the Securities Act
or any similar successor rule, as the same shall be in effect from time to time.

          "RULE 415" shall mean Rule 415 promulgated under the Securities Act,
or any similar successor rule, as the same shall be in effect from time to time.

          "SECURITIES ACT" shall mean the Securities Act of 1933, as amended
from time to time.


                                      2.
<PAGE>

          "SEC" shall mean the Securities and Exchange Commission.

          "UNDERWRITTEN OFFERING" shall mean a registration in which securities
of Tetra Tech are sold to an underwriter or through an underwriter as agent for
reoffering to the public.

     2.   TETRA TECH REGISTRATION.  If Tetra Tech shall determine to register
any shares of Tetra Tech Common Stock, or any securities convertible into or
exchangeable or exercisable for shares of Tetra Tech Common Stock, for its
own account or for the account of any stockholder (other than a registration
relating to the sale of securities to employees of Tetra Tech pursuant to an
employee benefit plan or pursuant to a transaction of the type described in
Rule 145 under the Securities Act), the Holders shall be entitled to include
Registrable Securities in such registration (and related underwritten
offering, if any) on the following terms and conditions:

          (a)  Tetra Tech shall promptly give written notice of such
determination to each Holder and each such Holder shall have the right to
request, by written notice given to Tetra Tech within 30 days of the receipt by
such Holder of such notice, that a specific number of Registrable Securities
held by such Holder be included in such Registration Statement;

          (b)  If the Registration Statement relates to an underwritten
offering, the notice called for by SECTION 2(a) shall specify the name of the
managing underwriter for such offering and the number of securities to be
registered for the account of Tetra Tech and for the account of any other
stockholder of Tetra Tech;

          (c)  If the Registration Statement relates to an underwritten
offering, each Holder to be included therein must (i) sell such person's
Registrable Securities on the same basis provided in the underwriting
arrangements approved by Tetra Tech and (ii) complete and execute all
questionnaires, powers of attorney, indemnities, hold-back agreements,
underwriting agreements and other documents required under the terms of such
underwriting arrangements or by the SEC;

          (d)  If the managing underwriter for the underwritten offering
under the Registration Statement to be filed by Tetra Tech determines that
inclusion of all or any portion of the Registrable Securities in such
offering would adversely affect the ability of the underwriter for such
offering to sell all of the securities requested to be included for sale or
the price per share in such offering, the number of shares that may be
included in such registration in such offering shall be allocated as follows:
(i) first, Tetra Tech shall be permitted to include all shares of capital
stock to be registered thereby; (ii) second, the Holders, on a pro rata basis
based on the total number of Registrable Securities held thereby (or on such
other basis as may be agreed among them), shall be allowed to include such
amount of the Registrable Securities as the managing underwriter deems
appropriate; and (iii) third, any other selling stockholder exercising
piggyback registration rights shall be allowed to include securities in such
amounts as may be deemed appropriate by such managing underwriter;


                                      3.
<PAGE>

          (e)  Holders shall have the right to withdraw their Registrable
Securities from the Registration Statement at any time prior to the effective
date thereof, but if the same relates to an underwritten offering, they may
only do so during the time period and on terms deemed appropriate by the
underwriters for such underwritten offering; and

          (f)  Tetra Tech shall have the right to terminate or withdraw any
registration initiated by it under this SECTION 2 prior to the effective date
of such registration for any reason without liability to any Holder as a
result thereof, whether or not any Holder has elected to include such
securities in such registration.

     3.   REGISTRATION FOR HOLDERS.

          (a)  Tetra Tech shall file a Registration Statement on Form S-3,
providing for the sale by the Holders, pursuant to Rule 415, and/or any
similar rule that may be adopted by the SEC, of the Registrable Securities.
Tetra Tech shall use commercially reasonable efforts to cause such
Registration Statement to become effective on or before May 7, 2000, and to
keep such Registration Statement continuously effective for a period ending
on the date on which all such Holders are eligible to sell Registrable
Securities under Rule 144 (or similar successor rule) without any volume
limitation. If, at the time Tetra Tech is required to file a Registration
Statement pursuant to this SECTION 3(a), Tetra Tech is not eligible to file a
Registration Statement on Form S-3 to register resales by stockholders, Tetra
Tech shall initially file a Registration Statement on Form S-1 and shall
comply with the provisions of the immediately preceding sentence. Upon
becoming eligible to use the Registration Statement on Form S-3 to register
resales by stockholders (whether pursuant to a ruling or waiver from the SEC
or otherwise), Tetra Tech shall promptly file a Registration Statement on
Form S-3 or convert the existing Registration Statement to Form S-3 relating
to the offer and sale of Registrable Securities by the Holders from time to
time. Thereafter, Tetra Tech shall use commercially reasonable efforts to
cause such new or amended Registration Statement to be declared effective by
the SEC as promptly as practicable.

          (b)  No Holder shall have the right to register securities under
this Agreement unless such Holder provides and/or confirms in writing prior
to or after the filing of the Registration Statement such information
(including, without limitation, information as to the number of Registrable
Securities that such Holder has sold pursuant to any such Registration
Statement from time to time) as Tetra Tech reasonably requests in connection
with such Registration Statement.

          (c)  Notwithstanding the foregoing, for a period not to exceed 90
days, Tetra Tech shall not be obligated to prepare and file the Registration
Statement required hereunder if Tetra Tech, in its good faith judgment,
reasonably believes that the filing of such Registration Statement would
require the disclosure of material non-public information regarding Tetra
Tech and, accordingly, that the filing thereof, at the time requested, or the
offering of Tetra Tech Common Stock pursuant thereto, would materially and
adversely affect (i) a pending or


                                      4.
<PAGE>

scheduled public offering or private placement of securities of Tetra Tech,
(ii) an acquisition, merger, consolidation or similar transaction by or of
Tetra Tech, (iii) preexisting and continuing negotiations, discussions or
pending proposals with respect to any of the foregoing transactions, or (iv)
the financial condition of Tetra Tech in view of the disclosure of any
pending or threatened litigation, claim, assessment or governmental
investigation which might be required thereby.

     In the event that Tetra Tech, in good faith, reasonably believes that
such conditions are continuing after such 90-day period, it may, with the
consent of the Holders of a majority of the Registrable Securities subject
(or to be subject) to the Registration Statement, which consent shall not be
unreasonably withheld, extend such 90-day period for an additional 30 days.
Any further delay shall require the consent of the Holders of all such shares.

     4.   RESTRICTIONS ON PUBLIC SALE BY HOLDERS OF REGISTRABLE SECURITIES.
Each Holder whose Registrable Securities are included (in whole or in part)
in a Registration Statement filed by Tetra Tech under SECTION 2 for sale in
an underwritten offering agrees, if requested by the managing underwriter of
such offering, not to sell, make any short sale of, loan, grant any option
for the purchase of, dispose of or effect any public sale or distribution of
securities of the same series and class as (or securities exchangeable or
exercisable for or convertible into securities of the same series and class
as) the Registrable Securities included in the Registration Statement,
including a sale pursuant to Rule 144 (except as part of such underwritten
registration), during the ten day period prior to, and during the 180 day
period (or shorter period requested by the underwriter) beginning on the
closing date of such underwritten offering, to the extent timely notified in
writing by Tetra Tech or the managing underwriter.

     5.   REGISTRATION PROCEDURES.  In connection with Tetra Tech's
registration obligations pursuant to SECTIONS 2 or 3 hereof, Tetra Tech will
use commercially reasonable efforts to effect such registration to permit the
sale of the Registrable Securities covered thereby in accordance with the
intended method or methods of disposition thereof, and pursuant thereto Tetra
Tech will:

          (a)  prepare and file with the SEC a Registration Statement with
respect to such Registrable Securities and use its commercially reasonable
efforts to cause such Registration Statement to become effective; PROVIDED that,
before filing any Registration Statement or Prospectus or any amendments or
supplements thereto, Tetra Tech will furnish to the Holders of the Registrable
Securities covered by such Registration Statement and their counsel, copies of
all such documents proposed to be filed at least ten days prior thereto, and
Tetra Tech will not file any such Registration Statement or amendment thereto or
any Prospectus or any supplement thereto to which any such Holder shall
reasonably object within such ten day period; PROVIDED, FURTHER, that Tetra Tech
will not name or otherwise provide any information with respect to any Holder in
any Registration Statement or Prospectus without the express written consent of
such Holder, unless required to do so by the Securities Act and the rules and
regulations thereunder;


                                      5.
<PAGE>

          (b)  prepare and file with the SEC such amendments, post-effective
amendments and supplements to the Registration Statement and the Prospectus
as may be necessary to comply with the provisions of the Securities Act and
the rules and regulations thereunder with respect to the disposition of all
securities covered by such Registration Statement;

          (c)  notify the selling Holders (i) when the Prospectus or any
Prospectus supplement or post-effective amendment has been filed, and, with
respect to the Registration Statement or any post-effective amendment, when
the same has become effective, (ii) of any request by the SEC for amendments
or supplements to the Registration Statement or the Prospectus or for
additional information, (iii) of the issuance by the SEC of any stop order
suspending the effectiveness of the Registration Statement or the initiation
of any proceedings for that purpose, (iv) of the receipt by Tetra Tech of any
notification with respect to the suspension of the qualification of the
Registrable Securities for sale in any jurisdiction or the initiation or
threatening of any proceeding for such purpose and (v) of the happening of
any event which makes any statement made in the Registration Statement, the
Prospectus or any document incorporated therein by reference untrue or which
requires the making of any changes in the Registration Statement, the
Prospectus or any document incorporated therein by reference in order to make
the statements therein not misleading in light of the circumstances then
existing;

          (d)  make every commercially reasonable effort to obtain the
withdrawal of any order suspending the effectiveness of the Registration
Statement at the earliest possible moment;

          (e)  deliver to each selling Holder, without charge, such
reasonable number of conformed copies of the Registration Statement (and any
post-effective amendment thereto) and such number of copies of the Prospectus
(including each preliminary prospectus) and any amendment or supplement
thereto (and any documents incorporated by reference therein) as such Holder
may reasonably request. Tetra Tech consents to the use of the Prospectus or
any amendment or supplement thereto by each of the selling Holders in
connection with the offer and sale of the Registrable Securities covered by
the Prospectus or any amendment or supplement thereto;

          (f)  prior to any offering of Registrable Securities covered by a
Registration Statement, register or qualify or cooperate with the selling
Holders in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or blue sky
laws of such jurisdictions as any such selling Holder reasonably requests,
and use commercially reasonable efforts to keep each such registration or
qualification effective, including through new filings, or amendments or
renewals, during the period such Registration Statement is required to be
kept effective pursuant to the terms of this Agreement; and do any and all
other acts or things necessary or advisable to enable the


                                      6.
<PAGE>

disposition in all such jurisdictions reasonably requested by the Holders of
the Registrable Securities covered by such Registration Statement, PROVIDED
that under no circumstances shall Tetra Tech be required in connection
therewith or as a condition thereof to qualify to do business or to file a
general consent to service of process in any such states or jurisdictions;

          (g)  cooperate with the selling Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities
to be sold, free of any and all restrictive legends, such certificates to be
in such denominations and registered in such names as the Holders may request;

          (h)  upon the occurrence of any event contemplated by SECTION 3(c)(v)
above, prepare a supplement or post-effective amendment to the Registration
Statement or the Prospectus or any document incorporated therein by reference or
file any other required document so that, as thereafter delivered to the
purchasers of the Registrable Securities, the Prospectus will not contain an
untrue statement of a material fact or omit to state any material fact necessary
to make the statements therein, in light of the circumstances under which they
were made, not misleading;

          (i)  make generally available to the holders of Tetra Tech's
outstanding securities earnings statements satisfying the provisions of
Section 11(a) of the Securities Act, no later than 60 days after the end of
any 12 month period (or 90 days, if such period is a fiscal year) beginning
with the first month of Tetra Tech's first fiscal quarter commencing after
the effective date of the Registration Statement, which statements shall
cover said 12 month period;

          (j)  provide and cause to be maintained a transfer agent and
registrar for all Registrable Securities covered by each Registration
Statement from and after a date not later than the effective date of such
Registration Statement;

          (k)  use its best efforts to cause all Registrable Securities
covered by each Registration Statement to be listed, subject to notice of
issuance, prior to the date of the first sale of such Registrable Securities
pursuant to such Registration Statement, on each securities exchange on which
the Tetra Tech Common Stock is then listed, and admitted to trading on the
Nasdaq Stock Market, if the Tetra Tech Common Stock is then admitted to
trading on the Nasdaq Stock Market; and

          (l)  enter into such agreements (including underwriting agreements
in customary form containing, among other things, reasonable and customary
indemnities) and take such other actions as a majority of the Holders shall
reasonably request in order to expedite or facilitate the disposition of such
Registrable Securities; and

          (m)  cooperate with the selling Holders and the managing
underwriter or underwriters in their marketing efforts with respect to the
sale of the Registrable Securities, including participation by Tetra Tech
management in "road show" presentations.


                                      7.
<PAGE>

     Each Holder agrees that, upon receipt of any notice from Tetra Tech of
the happening of any event of the kind described in SECTION 5(c)(v) hereof,
such Holder will forthwith discontinue disposition of Registrable Securities
under the Prospectus related to the applicable Registration Statement until
such Holder's receipt of the copies of the supplemented or amended Prospectus
contemplated by SECTION 5(h) hereof, or until it is advised in writing by
Tetra Tech that the use of the Prospectus may be resumed.

     It shall be a condition precedent to the obligations of Tetra Tech to
take any action pursuant to this SECTION 5 with respect to the Registrable
Securities of any selling Holder that such Holder shall furnish to Tetra Tech
such information regarding itself and the Registrable Securities held by it
as shall be required by the Securities Act to effect the registration of such
Holder's Registrable Securities.

     6.   REGISTRATION EXPENSES.  All expenses incident to any registration
to be effected hereunder and incident to Tetra Tech's performance of or
compliance with this Agreement, including without limitation all registration
and filing fees, fees and expenses of compliance with securities or blue sky
laws, printing expenses, messenger and delivery expenses, National
Association of Securities Dealers, Inc., stock exchange and qualification
fees, fees and disbursements of Tetra Tech's counsel and of independent
certified public accountants of Tetra Tech (including the expenses of any
special audit required by or incident to such performance), the fees and
disbursements of one counsel and one accountant representing the Holders in
such offering, expenses of the underwriters that are customarily requested in
similar circumstances by such underwriters (excluding discounts, commissions
or fees of underwriters, selling brokers, dealer managers or similar
securities industry professionals relating to the distribution of the
Registrable Securities, which will be borne by the Holders), all such
expenses being herein called "Registration Expenses," will be borne by Tetra
Tech. Tetra Tech will also pay its internal expenses, the expense of any
annual audit and the fees and expenses of any person retained by Tetra Tech.

     7.   INDEMNIFICATION.

          (a)  INDEMNIFICATION BY TETRA TECH.  Tetra Tech agrees to indemnify
and hold harmless each Holder of Registrable Securities, its officers,
directors, partners and employees and each person who controls such Holder
(within the meaning of Section 15 of the Securities Act) from and against any
and all losses, claims, damages and liabilities (including any investigation,
legal or other expenses reasonably incurred in connection with, and any
amount paid in settlement of, any action, suit or proceeding or any claim
asserted) (collectively, "Damages") to which such Holder may become subject
under the Securities Act, the Exchange Act or other federal or state
securities law or regulation, at common law or otherwise, insofar as such
Damages arise out of or are based upon (i) any untrue statement or alleged
untrue statement of a material fact contained in any Registration Statement,
Prospectus or preliminary prospectus or any amendment or supplement thereto,
(ii) the omission or


                                      8.
<PAGE>

alleged omission to state therein a 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 and (iii) any
violation or alleged violation by Tetra Tech of the Securities Act, the
Exchange Act or any state securities or blue sky laws in connection with the
Registration Statement, Prospectus or preliminary prospectus or any amendment
or supplement thereto, PROVIDED that Tetra Tech will not be liable to any
Holder to the extent that such Damages arise from or are based upon any
untrue statement or omission (x) based upon written information furnished to
Tetra Tech by such Holder expressly for the inclusion in such Registration
Statement, (y) made in any preliminary prospectus if such Holder failed to
deliver a copy of the Prospectus with or prior to the delivery of written
confirmation of the sale by such Holder to the party asserting the claim
underlying such Damages and such Prospectus would have corrected such untrue
statement or omission and (z) made in any Prospectus if such untrue statement
or omission was corrected in an amendment or supplement to such Prospectus
and such Holder failed to deliver such amendment or supplement prior to or
concurrently with the sale of Registrable Securities to the party asserting
the claim underlying such Damages.

          (b)  INDEMNIFICATION BY HOLDER OF REGISTRABLE SECURITIES.  Each
Holder of Registrable Securities whose Registrable Securities are sold under
a Prospectus which is a part of a Registration Statement agrees to indemnify
and hold harmless Tetra Tech, its directors and each officer who signed such
Registration Statement and each person who controls Tetra Tech (within the
meaning of Section 15 of the Securities Act), and each other Holder of
Registrable Securities whose Registrable Securities are sold under the
Prospectus which is a part of such Registration Statement (and such Holder's
officers, directors and employees and each person who controls such Holder
within the meaning of Section 15 of the Securities Act), under the same
circumstances as the foregoing indemnity from Tetra Tech to each Holder of
Registrable Securities to the extent that such losses, claims, damages,
liabilities or actions arise out of or are based upon any untrue statement of
a material fact or omission of a material fact that was made in the
Prospectus, the Registration Statement, or any amendment or supplement
thereto, in reliance upon and in conformity with information relating to such
Holder furnished in writing to Tetra Tech by such Holder expressly for use
therein, PROVIDED that in no event shall the aggregate liability of any
selling Holder of Registrable Securities exceed the amount of the net
proceeds received by such Holder upon the sale of the Registrable Securities
giving rise to such indemnification obligation. Tetra Tech and the selling
Holders shall be entitled to receive indemnities from underwriters, selling
brokers, dealer managers and similar securities industry professionals
participating in the distribution, to the same extent as customarily
furnished by such persons in similar circumstances.

          (c)  CONDUCT OF INDEMNIFICATION PROCEEDINGS.  Any person entitled
to indemnification hereunder will (i) give prompt notice to the indemnifying
party of any claim with respect to which it seeks indemnification and (ii)
permit such indemnifying party to assume the defense of such claim with
counsel reasonably satisfactory to the indemnified party; PROVIDED, HOWEVER,
that any person entitled to indemnification hereunder shall have the right to
employ separate counsel and to participate in the defense of such claim, but
the fees


                                      9.
<PAGE>

and expenses of such counsel shall be at the expense of such person and not
of the indemnifying party unless (A) the indemnifying party has agreed to pay
such fees or expenses, (B) the indemnifying party shall have failed to assume
the defense of such claim and employ counsel reasonably satisfactory to such
person or (C) in the reasonable judgment of such person and the indemnifying
party, based upon advice of their respective counsel, a conflict of interest
may exist between such person and the indemnifying party with respect to such
claims (in which case, if the person notifies the indemnifying party in
writing that such person elects to employ separate counsel at the expense of
the indemnifying party, the indemnifying party shall not have the right to
assume the defense of such claim on behalf of such person). If such defense
is not assumed by the indemnifying party, the indemnifying party will not be
subject to any liability for any settlement made without its consent (but
such consent will not be unreasonably withheld). No indemnified party will be
required to consent to entry of any judgment or enter into any settlement
which does not include as an unconditional term thereof the giving by all
claimants or plaintiffs to such indemnified party of a release from all
liability in respect to such claim or litigation. Any indemnifying party who
is not entitled to, or elects not to, assume the defense of a claim will not
be obligated to pay the fees and expenses of more than one counsel for all
parties indemnified by such indemnifying party with respect to such claim. As
used in this SECTION 7(c), the terms "indemnifying party", "indemnified
party" and other terms of similar import are intended to include only Tetra
Tech (and its officers, directors and control persons as set forth above) on
the one hand, and the Holders (and their officers, directors, partners,
employees, attorneys and control persons as set forth above) on the other
hand, as applicable.

          (d)  CONTRIBUTION.  If for any reason the foregoing indemnity is
unavailable, then the indemnifying party shall contribute to the amount paid
or payable by the indemnified party as a result of such losses, claims,
damages, liabilities or expenses (i) in such proportion as is appropriate to
reflect the relative fault of the indemnifying party and the indemnified
party in connection with the statements or omissions which resulted in such
losses, claims, damages, liabilities or expenses, as well as any other
relevant equitable considerations. The relative fault of such indemnifying
party and indemnified party shall be determined by reference to, among other
things, whether the untrue statement or alleged untrue statement of a
material fact or omission or alleged omission to state a material fact
relates to information supplied by such indemnifying party or by such
indemnified party, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The parties acknowledge and agree that it would not be just and equitable if
contribution pursuant to this SECTION 7(d) were determined by pro rata
allocation or by any other method of allocation which does not take into
account the equitable considerations referred to in this SECTION 7(d).
Notwithstanding the foregoing, no Holder shall be required to contribute any
amount in excess of the amount such Holder would have been required to pay to
an indemnified party if the indemnity under SECTION 7(b) hereof was
available. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent


                                      10.
<PAGE>

misrepresentation. The obligation of any person to contribute pursuant to
this SECTION 7(d) shall be several and not joint.

          (e)  TIMING OF PAYMENTS.  An indemnifying party shall make payments
of all amounts required to be made pursuant to the foregoing provisions of
this SECTION 7 to or for the account of the indemnified party from time to
time promptly upon receipt of bills or invoices relating thereto or when
otherwise due or payable.

          (f)  SURVIVAL.  The indemnity and contribution agreements contained
in this SECTION 7 shall remain in full force and effect, regardless of any
investigation made by or on behalf of Tetra Tech, a participating Holder, its
officers, directors, partners, attorneys, agents or any person, if any, who
controls Tetra Tech or such Holder as aforesaid, and shall survive the
transfer of such Registrable Securities by such Holder.

     8.   PREPARATION; REASONABLE INVESTIGATION.  In connection with the
preparation and filing of a Registration Statement pursuant to the terms of
this Agreement:

          (a)  Tetra Tech shall, with respect to a Registration Statement
filed pursuant to SECTION 3, give the Holders of such Registrable Securities
so registered, their underwriters, if any, and their respective counsel and
accountants the opportunity to participate in the preparation of such
Registration Statement (other than reports and proxy statements incorporated
therein by reference and properly filed with the SEC) and each Prospectus
included therein or filed with the SEC, and each amendment thereof or
supplement thereto; and

          (b)  Tetra Tech shall give the Holders of such Registrable
Securities so registered, their underwriters, if any, and their respective
counsel and accountants such reasonable access to its books and records and
such opportunities to discuss the business of Tetra Tech with its officers
and the independent public accountants who have certified its financial
statements as shall be necessary, in the opinion of such Holders or such
underwriters, to conduct a reasonable investigation within the meaning of
Section 11(b)(3) of the Securities Act.

     9.   RULE 144.  Tetra Tech covenants that it will use commercially
reasonable efforts to file, on a timely basis, the reports required to be
filed by it under the Securities Act and the Exchange Act and the rules and
regulations adopted by the SEC thereunder, and it will take such further
action as any Holder may reasonably request (including, without limitation,
compliance with the current public information requirements of Rule 144(c)
and Rule 144A), all to the extent required from time to time to enable such
Holder to sell Registrable Securities without registration under the
Securities Act within the limitation of the conditions provided by Rule 144,
Rule 144A or any similar rule or regulation hereafter adopted by the SEC.
Upon the request of any Holder, Tetra Tech will promptly deliver to such
Holder a written statement verifying that it has complied with such
information and requirements.


                                      11.
<PAGE>

     10.  SPECIFIC PERFORMANCE.  Each Holder, in addition to being entitled
to exercise all rights provided herein or granted by law, including recovery
of damages, will be entitled to specific performance of its rights under this
Agreement. Tetra Tech agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the
provisions of this Agreement and hereby agrees to waive the defense in any
action for specific performance that a remedy at law would be adequate.

     11.  NOTICES.  All notices and other communications required or
permitted hereunder shall be in writing and shall be mailed by United States
first-class mail, postage prepaid, sent by facsimile or delivered personally
by hand or nationally recognized courier addressed (a) if to a Holder, as
indicated on the list of Holders attached hereto as SCHEDULE A, or at such
other address as such Holder or permitted assignee shall have furnished to
Tetra Tech in writing, or (b) if to Tetra Tech, at such address or facsimile
number as Tetra Tech shall have furnished to each Holder in writing. All such
notices and other written communications shall be effective on the date of
mailing, facsimile transfer or delivery.

     12.  SUCCESSORS AND ASSIGNS: ASSIGNMENT OF RIGHTS.  The rights and
benefits of a Holder hereunder may not be assigned to a transferee or
assignee without the consent of Tetra Tech; PROVIDED, HOWEVER, that, no later
than the 10th day prior to the filing of the Registration Statement under
SECTION 3 hereof, the rights and benefits of a Holder hereunder may be
transferred in connection with a transfer or assignment of any Registrable
Securities held by such Holder (i) by gift to immediate family members of
such Holder, or trusts or other entities for the sole benefit thereof, or
(ii) by gift to any entity in which such Holder, his or her immediate family
members, or trusts or other entities for the sole benefit thereof
beneficially own all of the voting securities; PROVIDED, HOWEVER, that in
each case, the transferee executes an instrument pursuant to which the
transferee agrees to be bound by the terms and conditions hereof as a Holder,
and such other documents as Tetra Tech or its counsel may reasonably require,
after which, such transferee shall be deemed a "Holder" hereunder. Any
transfer of Registrable Securities, and rights hereunder, shall be subject to
compliance with applicable securities laws and the restrictions contained in
the Investment Letter executed by each Holder pursuant to the Stock Purchase
Agreement.

     13.  SEVERABILITY.  In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability
of any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

     14.  ENTIRE AGREEMENT; AMENDMENT; WAIVER.  This Agreement, the Stock
Purchase Agreement and the other agreements contemplated thereby constitute
the full and entire understanding and agreement among the parties with regard
to the subjects hereof and thereof. Without limiting the foregoing, the
rights of the Holders to registration pursuant to the terms of this Agreement
shall be subject to the limitations on resale contained in the Investment


                                      12.
<PAGE>

Letter (as defined in the Stock Purchase Agreement). Neither this Agreement
nor any term hereof may be amended, waived, discharged or terminated, except
by a written instrument signed by Tetra Tech and the holders of at least 51%
of the Registrable Securities and any such amendment, waiver, discharge or
termination shall be binding upon all the parties hereto, but in no event
shall the obligation of any party hereto be materially increased, except upon
the written consent of such party.

     15.  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be original, and all of which together
shall constitute one instrument.

     16.  GOVERNING LAW.  This Agreement shall be governed by, and construed
in accordance with, the laws of the State of Delaware without giving effect
to principles of conflicts of laws thereof.

     17.  NO THIRD PARTY BENEFICIARIES.  The covenants and agreements set
forth herein are for the sole and exclusive benefit of the parties hereto and
their respective successors and assigns and such covenants and agreements
shall not be construed as conferring, and are not intended to confer, any
rights or benefits upon any other persons.


                                      13.
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.


                                 TETRA TECH, INC.


                                 By: /s/ Li-San Hwang
                                     ---------------------------------
                                     Li-San Hwang
                                     Chairman, Chief Executive Officer
                                     and President


                                 Raul FCO G. Pina


                                      14.
<PAGE>

                                                                      SCHEDULE A

                               SCHEDULE OF HOLDERS

<TABLE>
<CAPTION>
                                                 Number of Shares of Tetra Tech
                                                 Common Stock Issued Pursuant
Holder's Name/Address/Facsimile No.              to the Stock Purchase Agreement
- -----------------------------------------        -------------------------------
<S>                                              <C>
Raul FCO G. Pina                                           4,938 shares
3801 E. Calle Guaymas
Tucson, Arizona 85716
Facsimile:  None

</TABLE>


                                      15.

<PAGE>

                                                                 EXHIBIT 10.27


                          REGISTRATION RIGHTS AGREEMENT

     This Registration Rights Agreement (the "Agreement") is entered into as
of May 21, 1999 by and among Tetra Tech, Inc., a Delaware corporation ("Tetra
Tech"), and the parties listed on SCHEDULE A attached hereto (each, a
"Holder" and collectively, the "Holders").

                                R E C I T A L S

     A.   Tetra Tech and the Holders are parties to an Agreement and Plan of
Reorganization of even date (the "Reorganization Agreement"), pursuant to
which BAHA Acquisition Corporation, a Nevada corporation and wholly-owned
subsidiary of Tetra Tech, will merge with and into BAHA Communications, Inc.,
a Nevada corporation ("BAHA").

     B.   Pursuant to the Reorganization Agreement, the shareholders of BAHA
will receive shares of the common stock, $.01 par value, of Tetra Tech
("Tetra Tech Common Stock"); and

     C.   This Agreement is the Registration Rights Agreement referred to in
SECTION 6.2 of the Reorganization Agreement and, pursuant thereto, must be
entered into by the parties in connection with the consummation of the
transactions contemplated by the Reorganization Agreement.


                                A G R E E M E N T

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

     1.   CERTAIN DEFINITIONS.  As used in this Agreement, the following
terms shall have the following respective meanings:

          "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as
amended from time to time.


<PAGE>

          "FORM S-3" shall mean such form under the Securities Act as in
effect on the date hereof or any successor registration form under the
Securities Act subsequently adopted by the SEC which permits inclusion or
incorporation of substantial information by reference to other documents
filed by Tetra Tech with the SEC.

          "PROSPECTUS" shall mean the prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement, with
respect to the terms of the offering of any portion of the Registrable
Securities covered by the Registration Statement and by all other amendments
and supplements to the prospectus, including post-effective amendments and
all material incorporated by reference in such Prospectus.

          "REGISTER", "REGISTERED" and "REGISTRATION" shall mean and refer to
a registration effected by preparing and filing a Registration Statement and
taking all other actions that are necessary or appropriate in connection
therewith, and the declaration or ordering of effectiveness of such
Registration Statement by the SEC.

          "REGISTRATION EXPENSES" shall have the meaning set forth in
SECTION 4.

          "REGISTRABLE SECURITIES" shall mean the shares of Tetra Tech Common
Stock (i) issued pursuant to the Reorganization Agreement, and (ii) issued as
a dividend or other distribution with respect to or in exchange for or in
replacement of the shares referenced in (i) above; PROVIDED, HOWEVER, that
Registrable Securities shall not include any shares of Tetra Tech Common
Stock that have previously been registered or sold to the public or have been
sold pursuant to Rule 144 (or similar successor Rule).

          "REGISTRATION STATEMENT" shall mean any registration statement of
Tetra Tech in compliance with the Securities Act that covers Registrable
Securities pursuant to the provisions of this Agreement, including, without
limitation, the Prospectus, all amendments and supplements to such
Registration Statement, including all post-effective amendments, all exhibits
and all material incorporated by reference in such Registration Statement.

          "RULE 144" shall mean Rule 144 promulgated under the Securities Act
or any similar successor rule, as the same shall be in effect from time to
time.

          "RULE 144A" shall mean Rule 144A promulgated under the Securities
Act or any similar successor rule, as the same shall be in effect from time
to time.

          "RULE 415" shall mean Rule 415 promulgated under the Securities
Act, or any similar successor rule, as the same shall be in effect from time
to time.

          "SECURITIES ACT" shall mean the Securities Act of 1933, as amended
from time to time.


                                       2.
<PAGE>

          "SEC" shall mean the Securities and Exchange Commission.

          "UNDERWRITTEN OFFERING" shall mean a registration in which
securities of Tetra Tech are sold to an underwriter or through an underwriter
as agent for reoffering to the public.

     2.   REGISTRATION.

          (a)  Tetra Tech shall file a Registration Statement on Form S-3,
providing for the sale by the Holders, pursuant to Rule 415, and/or any
similar rule that may be adopted by the SEC, of the Registrable Securities.
Tetra Tech shall use commercially reasonable efforts to cause such
Registration Statement to become effective on or before November 21, 1999,
and to keep such Registration Statement continuously effective for a period
ending on the date on such all Holders are eligible to sell Registrable
Securities under Rule 144 (or similar successor rule) without any volume
limitation. If, at the time Tetra Tech is required to file a Registration
Statement pursuant to this SECTION 2(a), Tetra Tech is not eligible to file a
Registration Statement on Form S-3 to register resales by stockholders, Tetra
Tech shall initially file a Registration Statement on Form S-1 and shall
comply with the provisions of the immediately preceding sentence. Upon
becoming eligible to use the Registration Statement on Form S-3 to register
resales by stockholders (whether pursuant to a ruling or waiver from the SEC
or otherwise), Tetra Tech shall promptly file a Registration Statement on
Form S-3 or convert the existing Registration Statement to Form S-3 relating
to the offer and sale of Registrable Securities by the Holders from time to
time. Thereafter, Tetra Tech shall use commercially reasonable efforts to
cause such new or amended Registration Statement to be declared effective by
the SEC as promptly as practicable.

          (b)  No Holder shall have the right to register securities under
this Agreement unless such Holder provides and/or confirms in writing prior
to or after the filing of the Registration Statement such information
(including, without limitation, information as to the number of Registrable
Securities that such Holder has sold pursuant to any such Registration
Statement from time to time) as Tetra Tech reasonably requests in connection
with such Registration Statement.

          (c)  Notwithstanding the foregoing, for a period not to exceed 90
days, Tetra Tech shall not be obligated to prepare and file the Registration
Statement required hereunder if Tetra Tech, in its good faith judgment,
reasonably believes that the filing of such Registration Statement would
require the disclosure of material non-public information regarding Tetra
Tech and, accordingly, that the filing thereof, at the time requested, or the
offering of Tetra Tech Common Stock pursuant thereto, would materially and
adversely affect (i) a pending or scheduled public offering or private
placement of securities of Tetra Tech, (ii) an acquisition, merger,
consolidation or similar transaction by or of Tetra Tech, (iii) preexisting
and continuing negotiations, discussions or pending proposals with respect to
any of the foregoing transactions, or (iv) the financial condition of Tetra
Tech in view of the disclosure of any


                                       3.
<PAGE>

pending or threatened litigation, claim, assessment or governmental
investigation which might be required thereby.

     In the event that Tetra Tech, in good faith, reasonably believes that
such conditions are continuing after such 90-day period, it may, with the
consent of the Holders of a majority of the Registrable Securities subject
(or to be subject) to the Registration Statement, which consent shall not be
unreasonably withheld, extend such 90-day period for an additional 30 days.
Any further delay shall require the consent of the Holders of all such shares.

     3.   REGISTRATION PROCEDURES.  In connection with Tetra Tech's
registration obligations pursuant to SECTION 2 hereof, Tetra Tech will use
commercially reasonable efforts to effect such registration to permit the
sale of the Registrable Securities covered thereby in accordance with the
intended method or methods of disposition thereof, and pursuant thereto Tetra
Tech will as expeditiously as possible:

          (a)  prepare and file with the SEC a Registration Statement with
respect to such Registrable Securities and use its commercially reasonable
efforts to cause such Registration Statement to become effective; PROVIDED
that, before filing any Registration Statement or Prospectus or any
amendments or supplements thereto, Tetra Tech will furnish to the Holders of
the Registrable Securities covered by such Registration Statement and their
counsel, copies of all such documents proposed to be filed at least ten days
prior thereto, and Tetra Tech will not file any such Registration Statement
or amendment thereto or any Prospectus or any supplement thereto to which any
such Holder shall reasonably object within such ten day period; PROVIDED,
FURTHER, that Tetra Tech will not name or otherwise provide any information
with respect to any Holder in any Registration Statement or Prospectus
without the express written consent of such Holder, unless required to do so
by the Securities Act and the rules and regulations thereunder;

          (b)  prepare and file with the SEC such amendments, post-effective
amendments and supplements to the Registration Statement and the Prospectus
as may be necessary to comply with the provisions of the Securities Act and
the rules and regulations thereunder with respect to the disposition of all
securities covered by such Registration Statement;

          (c)  notify the selling Holders (i) when the Prospectus or any
Prospectus supplement or post-effective amendment has been filed, and, with
respect to the Registration Statement or any post-effective amendment, when
the same has become effective, (ii) of any request by the SEC for amendments
or supplements to the Registration Statement or the Prospectus or for
additional information, (iii) of the issuance by the SEC of any stop order
suspending the effectiveness of the Registration Statement or the initiation
of any proceedings for that purpose, (iv) of the receipt by Tetra Tech of any
notification with respect to the suspension of the qualification of the
Registrable Securities for sale in any jurisdiction or the initiation or
threatening of any proceeding for such purpose and (v) of the happening of
any event which makes any statement made in the Registration Statement, the
Prospectus or any


                                       4.
<PAGE>

document incorporated therein by reference untrue or which requires the
making of any changes in the Registration Statement, the Prospectus or any
document incorporated therein by reference in order to make the statements
therein not misleading in light of the circumstances then existing;

          (d)  make every commercially reasonable effort to obtain the
withdrawal of any order suspending the effectiveness of the Registration
Statement at the earliest possible moment;

          (e)  deliver to each selling Holder, without charge, such
reasonable number of conformed copies of the Registration Statement (and any
post-effective amendment thereto) and such number of copies of the Prospectus
(including each preliminary prospectus) and any amendment or supplement
thereto (and any documents incorporated by reference therein) as such Holder
may reasonably request. Tetra Tech consents to the use of the Prospectus or
any amendment or supplement thereto by each of the selling Holders in
connection with the offer and sale of the Registrable Securities covered by
the Prospectus or any amendment or supplement thereto;

          (f)  prior to any offering of Registrable Securities covered by a
Registration Statement, register or qualify or cooperate with the selling
Holders in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or blue sky
laws of such jurisdictions as any such selling Holder reasonably requests,
and use commercially reasonable efforts to keep each such registration or
qualification effective, including through new filings, or amendments or
renewals, during the period such Registration Statement is required to be
kept effective pursuant to the terms of this Agreement; and do any and all
other acts or things necessary or advisable to enable the disposition in all
such jurisdictions reasonably requested by the Holders of the Registrable
Securities covered by such Registration Statement, PROVIDED that under no
circumstances shall Tetra Tech be required in connection therewith or as a
condition thereof to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions;

          (g)  cooperate with the selling Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities
to be sold, free of any and all restrictive legends, such certificates to be
in such denominations and registered in such names as the Holders may request;

          (h)  upon the occurrence of any event contemplated by SECTION
3(c)(v) above, prepare a supplement or post-effective amendment to the
Registration Statement or the Prospectus or any document incorporated therein
by reference or file any other required document so that, as thereafter
delivered to the purchasers of the Registrable Securities, the Prospectus
will not contain an untrue statement of a material fact or omit to state any
material fact necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading;


                                       5.

<PAGE>

          (i)  make generally available to the holders of Tetra Tech's
outstanding securities earnings statements satisfying the provisions of
Section 11(a) of the Securities Act, no later than 60 days after the end of
any 12 month period (or 90 days, if such period is a fiscal year) beginning
with the first month of Tetra Tech's first fiscal quarter commencing after
the effective date of the Registration Statement, which statements shall
cover said 12 month period;

          (j)  provide and cause to be maintained a transfer agent and
registrar for all Registrable Securities covered by each Registration
Statement from and after a date not later than the effective date of such
Registration Statement;

          (k)  use its best efforts to cause all Registrable Securities
covered by each Registration Statement to be listed, subject to notice of
issuance, prior to the date of the first sale of such Registrable Securities
pursuant to such Registration Statement, on each securities exchange on which
the Tetra Tech Common Stock is then listed, and admitted to trading on the
Nasdaq Stock Market, if the Tetra Tech Common Stock is then admitted to
trading on the Nasdaq Stock Market; and

          (l)  enter into such agreements and take such other actions as a
majority of the Holders shall reasonably request in order to expedite or
facilitate the disposition of such Registrable Securities.

     Each Holder agrees that, upon receipt of any notice from Tetra Tech of
the happening of any event of the kind described in SECTION 3(c)(v) hereof,
such Holder will forthwith discontinue disposition of Registrable Securities
under the Prospectus related to the applicable Registration Statement until
such Holder's receipt of the copies of the supplemented or amended Prospectus
contemplated by SECTION 3(h) hereof, or until it is advised in writing by
Tetra Tech that the use of the Prospectus may be resumed.

     It shall be a condition precedent to the obligations of Tetra Tech to
take any action pursuant to this SECTION 3 with respect to the Registrable
Securities of any selling Holder that such Holder shall furnish to Tetra Tech
such information regarding itself and the Registrable Securities held by it
as shall be required by the Securities Act to effect the registration of such
Holder's Registrable Securities.

     4.   REGISTRATION EXPENSES.  All expenses incident to any registration
to be effected hereunder and incident to Tetra Tech's performance of or
compliance with this Agreement, including without limitation all registration
and filing fees, fees and expenses of compliance with securities or blue sky
laws, printing expenses, messenger and delivery expenses, National
Association of Securities Dealers, Inc., stock exchange and qualification
fees, fees and disbursements of Tetra Tech's counsel and of independent
certified public accountants of Tetra Tech (including the expenses of any
special audit required by or incident to such


                                       6.
<PAGE>

performance), the fees and disbursements of one counsel and one accountant
representing the Holders in such offering, expenses of the underwriters that
are customarily requested in similar circumstances by such underwriters
(excluding discounts, commissions or fees of underwriters, selling brokers,
dealer managers or similar securities industry professionals relating to the
distribution of the Registrable Securities, which will be borne by the
Holders), all such expenses being herein called "Registration Expenses," will
be borne by Tetra Tech. Tetra Tech will also pay its internal expenses, the
expense of any annual audit and the fees and expenses of any person retained
by Tetra Tech.

     5.   INDEMNIFICATION.

          (a)  INDEMNIFICATION BY TETRA TECH.  Tetra Tech agrees to indemnify
and hold harmless each Holder of Registrable Securities, its officers,
directors, partners and employees and each person who controls such Holder
(within the meaning of Section 15 of the Securities Act) from and against any
and all losses, claims, damages and liabilities (including any investigation,
legal or other expenses reasonably incurred in connection with, and any
amount paid in settlement of, any action, suit or proceeding or any claim
asserted) (collectively, "Damages") to which such Holder may become subject
under the Securities Act, the Exchange Act or other federal or state
securities law or regulation, at common law or otherwise, insofar as such
Damages arise out of or are based upon (i) any untrue statement or alleged
untrue statement of a material fact contained in any Registration Statement,
Prospectus or preliminary prospectus or any amendment or supplement thereto,
(ii) the omission or alleged omission to state therein a 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 and
(iii) any violation or alleged violation by Tetra Tech of the Securities Act,
the Exchange Act or any state securities or blue sky laws in connection with
the Registration Statement, Prospectus or preliminary prospectus or any
amendment or supplement thereto, PROVIDED that Tetra Tech will not be liable
to any Holder to the extent that such Damages arise from or are based upon
any untrue statement or omission (x) based upon written information furnished
to Tetra Tech by such Holder expressly for the inclusion in such Registration
Statement, (y) made in any preliminary prospectus if such Holder failed to
deliver a copy of the Prospectus with or prior to the delivery of written
confirmation of the sale by such Holder to the party asserting the claim
underlying such Damages and such Prospectus would have corrected such untrue
statement or omission and (z) made in any Prospectus if such untrue statement
or omission was corrected in an amendment or supplement to such Prospectus
and such Holder failed to deliver such amendment or supplement prior to or
concurrently with the sale of Registrable Securities to the party asserting
the claim underlying such Damages.

          (b)  INDEMNIFICATION BY HOLDER OF REGISTRABLE SECURITIES.  Each
Holder of Registrable Securities whose Registrable Securities are sold under
a Prospectus which is a part of a Registration Statement agrees to indemnify
and hold harmless Tetra Tech, its directors and each officer who signed such
Registration Statement and each person who controls Tetra Tech (within the
meaning of Section 15 of the Securities Act), and each other Holder of


                                       7.
<PAGE>

Registrable Securities whose Registrable Securities are sold under the
Prospectus which is a part of such Registration Statement (and such Holder's
officers, directors and employees and each person who controls such Holder
within the meaning of Section 15 of the Securities Act), under the same
circumstances as the foregoing indemnity from Tetra Tech to each Holder of
Registrable Securities to the extent that such losses, claims, damages,
liabilities or actions arise out of or are based upon any untrue statement of
a material fact or omission of a material fact that was made in the
Prospectus, the Registration Statement, or any amendment or supplement
thereto, in reliance upon and in conformity with information relating to such
Holder furnished in writing to Tetra Tech by such Holder expressly for use
therein, PROVIDED that in no event shall the aggregate liability of any
selling Holder of Registrable Securities exceed the amount of the net
proceeds received by such Holder upon the sale of the Registrable Securities
giving rise to such indemnification obligation. Tetra Tech and the selling
Holders shall be entitled to receive indemnities from underwriters, selling
brokers, dealer managers and similar securities industry professionals
participating in the distribution, to the same extent as customarily
furnished by such persons in similar circumstances.

          (c)  CONDUCT OF INDEMNIFICATION PROCEEDINGS.  Any person entitled
to indemnification hereunder will (i) give prompt notice to the indemnifying
party of any claim with respect to which it seeks indemnification and (ii)
permit such indemnifying party to assume the defense of such claim with
counsel reasonably satisfactory to the indemnified party; PROVIDED, HOWEVER,
that any person entitled to indemnification hereunder shall have the right to
employ separate counsel and to participate in the defense of such claim, but
the fees and expenses of such counsel shall be at the expense of such person
and not of the indemnifying party unless (A) the indemnifying party has
agreed to pay such fees or expenses, (B) the indemnifying party shall have
failed to assume the defense of such claim and employ counsel reasonably
satisfactory to such person or (C) in the reasonable judgment of such person
and the indemnifying party, based upon advice of their respective counsel, a
conflict of interest may exist between such person and the indemnifying party
with respect to such claims (in which case, if the person notifies the
indemnifying party in writing that such person elects to employ separate
counsel at the expense of the indemnifying party, the indemnifying party
shall not have the right to assume the defense of such claim on behalf of
such person). If such defense is not assumed by the indemnifying party, the
indemnifying party will not be subject to any liability for any settlement
made without its consent (but such consent will not be unreasonably
withheld). No indemnified party will be required to consent to entry of any
judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by all claimants or plaintiffs to such
indemnified party of a release from all liability in respect to such claim or
litigation. Any indemnifying party who is not entitled to, or elects not to,
assume the defense of a claim will not be obligated to pay the fees and
expenses of more than one counsel for all parties indemnified by such
indemnifying party with respect to such claim. As used in this SECTION 5(c),
the terms "indemnifying party", "indemnified party" and other terms of
similar import are intended to include only Tetra Tech (and its officers,
directors and control persons as set forth above) on the one hand, and the
Holders (and their


                                       8.
<PAGE>

officers, directors, partners, employees, attorneys and
control persons as set forth above) on the other hand, as applicable.

          (d)  CONTRIBUTION.  If for any reason the foregoing indemnity is
unavailable, then the indemnifying party shall contribute to the amount paid
or payable by the indemnified party as a result of such losses, claims,
damages, liabilities or expenses (i) in such proportion as is appropriate to
reflect the relative fault of the indemnifying party and the indemnified
party in connection with the statements or omissions which resulted in such
losses, claims, damages, liabilities or expenses, as well as any other
relevant equitable considerations. The relative fault of such indemnifying
party and indemnified party shall be determined by reference to, among other
things, whether the untrue statement or alleged untrue statement of a
material fact or omission or alleged omission to state a material fact
relates to information supplied by such indemnifying party or by such
indemnified party, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The parties acknowledge and agree that it would not be just and equitable if
contribution pursuant to this SECTION 5(d) were determined by pro rata
allocation or by any other method of allocation which does not take into
account the equitable considerations referred to in this SECTION 5(d).
Notwithstanding the foregoing, no Holder shall be required to contribute any
amount in excess of the amount such Holder would have been required to pay to
an indemnified party if the indemnity under Section 5(b) hereof was
available. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The obligation of any person to contribute pursuant to
this SECTION 5(d) shall be several and not joint.

          (e)  TIMING OF PAYMENTS.  An indemnifying party shall make payments
of all amounts required to be made pursuant to the foregoing provisions of
this SECTION 5 to or for the account of the indemnified party from time to
time promptly upon receipt of bills or invoices relating thereto or when
otherwise due or payable.

          (f)  SURVIVAL.  The indemnity and contribution agreements contained
in this SECTION 5 shall remain in full force and effect, regardless of any
investigation made by or on behalf of Tetra Tech, a participating Holder, its
officers, directors, partners, attorneys, agents or any person, if any, who
controls Tetra Tech or such Holder as aforesaid, and shall survive the
transfer of such Registrable Securities by such Holder.

     6.   PREPARATION; REASONABLE INVESTIGATION.  In connection with the
preparation and filing of a Registration Statement pursuant to the terms of
this Agreement:

          (a)  Tetra Tech shall, with respect to a Registration Statement filed
pursuant to SECTION 2, give the Holders of such Registrable Securities so
registered, their underwriters, if any, and their respective counsel and
accountants the opportunity to participate in the preparation of such
Registration Statement (other than reports and proxy statements incorporated
therein by reference and properly filed with the SEC) and each Prospectus


                                       9.
<PAGE>

included therein or filed with the SEC, and each amendment thereof or
supplement thereto; and

          (b)  Tetra Tech shall give the Holders of such Registrable
Securities so registered, their underwriters, if any, and their respective
counsel and accountants such reasonable access to its books and records and
such opportunities to discuss the business of Tetra Tech with its officers
and the independent public accountants who have certified its financial
statements as shall be necessary, in the opinion of such Holders or such
underwriters, to conduct a reasonable investigation within the meaning of
Section 11(b)(3) of the Securities Act.

     7.   RULE 144.  Tetra Tech covenants that it will use commercially
reasonable efforts to file, on a timely basis, the reports required to be
filed by it under the Securities Act and the Exchange Act and the rules and
regulations adopted by the SEC thereunder, and it will take such further
action as any Holder may reasonably request (including, without limitation,
compliance with the current public information requirements of Rule 144(c)
and Rule 144A), all to the extent required from time to time to enable such
Holder to sell Registrable Securities without registration under the
Securities Act within the limitation of the conditions provided by Rule 144,
Rule 144A or any similar rule or regulation hereafter adopted by the SEC.
Upon the request of any Holder, Tetra Tech will promptly deliver to such
Holder a written statement verifying that it has complied with such
information and requirements.

     8.   SPECIFIC PERFORMANCE.  Each Holder, in addition to being entitled
to exercise all rights provided herein or granted by law, including recovery
of damages, will be entitled to specific performance of its rights under this
Agreement. Tetra Tech agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the
provisions of this Agreement and hereby agrees to waive the defense in any
action for specific performance that a remedy at law would be adequate.

     9.   NOTICES.  All notices and other communications required or
permitted hereunder shall be in writing and shall be mailed by United States
first-class mail, postage prepaid, sent by facsimile or delivered personally
by hand or nationally recognized courier addressed (a) if to a Holder, as
indicated on the list of Holders attached hereto as SCHEDULE A, or at such
other address as such Holder or permitted assignee shall have furnished to
Tetra Tech in writing, or (b) if to Tetra Tech, at such address or facsimile
number as Tetra Tech shall have furnished to each Holder in writing. All such
notices and other written communications shall be effective on the date of
mailing, facsimile transfer or delivery.

     10.  SUCCESSORS AND ASSIGNS: ASSIGNMENT OF RIGHTS.  The rights and
benefits of a Holder hereunder may not be assigned to a transferee or
assignee without the consent of Tetra Tech; PROVIDED, HOWEVER, that, no later
than the 10th day prior to the filing of the Registration Statement under
SECTION 2 hereof, the rights and benefits of a Holder hereunder may be
transferred in connection with a transfer or assignment of any Registrable
Securities held by such Holder (i) by gift to immediate family members of
such Holder, or trusts or other entities


                                       10.
<PAGE>

for the sole benefit thereof, or (ii) by gift to any entity in which such
Holder, his or her immediate family members, or trusts or other entities for
the sole benefit thereof beneficially own all of the voting securities;
PROVIDED, HOWEVER, that in each case, the transferee executes an instrument
pursuant to which the transferee agrees to be bound by the terms and
conditions hereof as a Holder, and such other documents as Tetra Tech or its
counsel may reasonably require, after which, such transferee shall be deemed
a "Holder" hereunder. Any transfer of Registrable Securities, and rights
hereunder, shall be subject to compliance with applicable securities laws and
the restrictions contained in the Investment Letter executed by each Holder
pursuant to the Reorganization Agreement.

     11.  SEVERABILITY.  In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability
of any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

     12.  ENTIRE AGREEMENT; AMENDMENT; WAIVER.  This Agreement, the
Reorganization Agreement and the other agreements contemplated thereby
constitute the full and entire understanding and agreement among the parties
with regard to the subjects hereof and thereof. Without limiting the
foregoing, the rights of the Holders to registration pursuant to the terms of
this Agreement shall be subject to the limitations on resale contained in the
Investment Letter (as defined in the Reorganization Agreement). Neither this
Agreement nor any term hereof may be amended, waived, discharged or
terminated, except by a written instrument signed by Tetra Tech and the
holders of at least 51% of the Registrable Securities and any such amendment,
waiver, discharge or termination shall be binding upon all the parties
hereto, but in no event shall the obligation of any party hereto be
materially increased, except upon the written consent of such party.

     13.  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be original, and all of which together
shall constitute one instrument.

     14.  GOVERNING LAW.  This Agreement shall be governed by, and construed
in accordance with, the laws of the State of California without giving effect
to principles of conflicts of laws thereof.

     15.  NO THIRD PARTY BENEFICIARIES.  The covenants and agreements set
forth herein are for the sole and exclusive benefit of the parties hereto and
their respective successors and assigns and such covenants and agreements
shall not be construed as conferring, and are not intended to confer, any
rights or benefits upon any other persons.


                                       11.
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                            TETRA TECH, INC.

                            By: /s/ Li-San Hwang
                                -------------------------------------------
                                Li-San Hwang
                                Chairman, Chief Executive Officer
                                and President


                            HOLDERS:


                            Tim Baker


                            Mark Baker


                            Dennis Baker


                                       12.
<PAGE>

                                                                      SCHEDULE A

                               SCHEDULE OF HOLDERS

<TABLE>
<CAPTION>
                                              Number of Initial Shares and
                                              Escrowed Shares of Tetra Tech
                                              Common Stock Issued Pursuant
Holder's Name/Address/Facsimile No.           to the Reorganization Agreement
- ---------------------------------------       -------------------------------
<S>                                           <C>

Tim Baker                                     80,793 shares
2900 Sunlit Glade
Henderson, Nevada 89014
Facsimile: ___________



Mark Baker                                    36,724 shares
8883 E. Captain Dreyfus
Scottsdale, Arizona 85260
Facsimile:  ___________



Dennis Baker                                  29,379 shares
1690 Cornice Road
P.O. Box 882050
Steamboat Springs, Colorado 80487
Facsimile:  ___________
</TABLE>


                                       13.

<PAGE>

                                                                  EXHIBIT 10.28


                          REGISTRATION RIGHTS AGREEMENT

     This Registration Rights Agreement (the "Agreement") is entered into as of
June 18, 1999 by and among Tetra Tech, Inc., a Delaware corporation ("Tetra
Tech"), and the parties listed on SCHEDULE A attached hereto (each, a "Holder"
and collectively, the "Holders").


                                 R E C I T A L S

     A.   Tetra Tech and the Holders are parties to an Agreement and Plan of
Reorganization of even date (the "Reorganization Agreement"), pursuant to which
UCCI Acquisition Corporation, a Delaware corporation and wholly-owned subsidiary
of Tetra Tech, will merge with and into Utilities & C.C., Inc., a California
corporation ("UCCI").

     B.   Pursuant to the Reorganization Agreement, the shareholders of UCCI
will receive shares of the common stock, $.01 par value, of Tetra Tech
("Tetra Tech Common Stock"); and

     C.   This Agreement is the Registration Rights Agreement referred to in
SECTION 6.2 of the Reorganization Agreement and, pursuant thereto, must be
entered into by the parties in connection with the consummation of the
transactions contemplated by the Reorganization Agreement.


                                A G R E E M E N T

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

     1.   CERTAIN DEFINITIONS.  As used in this Agreement, the following
terms shall have the following respective meanings:

          "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as
amended from time to time.

          "FORM S-3" shall mean such form under the Securities Act as in effect
on the date hereof or any successor registration form under the Securities Act
subsequently adopted by the


<PAGE>

SEC which permits inclusion or incorporation of substantial information by
reference to other documents filed by Tetra Tech with the SEC.

          "PROSPECTUS" shall mean the prospectus included in any Registration
Statement, as amended or supplemented by any prospectus supplement, with
respect to the terms of the offering of any portion of the Registrable
Securities covered by the Registration Statement and by all other amendments
and supplements to the prospectus, including post-effective amendments and
all material incorporated by reference in such Prospectus.

          "REGISTER", "REGISTERED" and "REGISTRATION" shall mean and refer to
a registration effected by preparing and filing a Registration Statement and
taking all other actions that are necessary or appropriate in connection
therewith, and the declaration or ordering of effectiveness of such
Registration Statement by the SEC.

          "REGISTRATION EXPENSES" shall have the meaning set forth in
SECTION 4.

          "REGISTRABLE SECURITIES" shall mean the shares of Tetra Tech Common
Stock (i) issued pursuant to the Reorganization Agreement, and (ii) issued as
a dividend or other distribution with respect to or in exchange for or in
replacement of the shares referenced in (i) above; PROVIDED, HOWEVER, that
Registrable Securities shall not include any shares of Tetra Tech Common
Stock that have previously been registered or sold to the public or have been
sold pursuant to Rule 144 ( or similar successor Rule).

          "REGISTRATION STATEMENT" shall mean any registration statement of
Tetra Tech in compliance with the Securities Act that covers Registrable
Securities pursuant to the provisions of this Agreement, including, without
limitation, the Prospectus, all amendments and supplements to such
Registration Statement, including all post-effective amendments, all exhibits
and all material incorporated by reference in such Registration Statement.

          "RULE 144" shall mean Rule 144 promulgated under the Securities Act
or any similar successor rule, as the same shall be in effect from time to
time.

          "RULE 144A" shall mean Rule 144A promulgated under the Securities
Act or any similar successor rule, as the same shall be in effect from time
to time.

          "RULE 415" shall mean Rule 415 promulgated under the Securities
Act, or any similar successor rule, as the same shall be in effect from time
to time.

          "SECURITIES ACT" shall mean the Securities Act of 1933, as amended
from time to time.

          "SEC" shall mean the Securities and Exchange Commission.


                                      2
<PAGE>

          "UNDERWRITTEN OFFERING" shall mean a registration in which
securities of Tetra Tech are sold to an underwriter or through an underwriter
as agent for reoffering to the public.

     2.   REGISTRATION.

          (a)  Tetra Tech shall file a Registration Statement on Form S-3,
providing for the sale by the Holders, pursuant to Rule 415, and/or any
similar rule that may be adopted by the SEC, of the Registrable Securities.
Tetra Tech shall use commercially reasonable efforts to cause such
Registration Statement to become effective on or before October 18, 1999, and
to keep such Registration Statement continuously effective for a period
ending on the date on which all such Holders are eligible to sell Registrable
Securities under Rule 144 (or similar successor rule) without any volume
limitation. If, at the time Tetra Tech is required to file a Registration
Statement pursuant to this SECTION 2(a), Tetra Tech is not eligible to file a
Registration Statement on Form S-3 to register resales by stockholders, Tetra
Tech shall initially file a Registration Statement on Form S-1 and shall
comply with the provisions of the immediately preceding sentence. Upon
becoming eligible to use the Registration Statement on Form S-3 to register
resales by stockholders (whether pursuant to a ruling or waiver from the SEC
or otherwise), Tetra Tech shall promptly file a Registration Statement on
Form S-3 or convert the existing Registration Statement to Form S-3 relating
to the offer and sale of Registrable Securities by the Holders from time to
time. Thereafter, Tetra Tech shall use commercially reasonable efforts to
cause such new or amended Registration Statement to be declared effective by
the SEC as promptly as practicable.

          (b)  No Holder shall have the right to register securities under
this Agreement unless such Holder provides and/or confirms in writing prior
to or after the filing of the Registration Statement such information
(including, without limitation, information as to the number of Registrable
Securities that such Holder has sold pursuant to any such Registration
Statement from time to time) as Tetra Tech reasonably requests in connection
with such Registration Statement.

          (c)  Notwithstanding the foregoing, for a period not to exceed 90
days, Tetra Tech shall not be obligated to prepare and file the Registration
Statement required hereunder if Tetra Tech, in its good faith judgment,
reasonably believes that the filing of such Registration Statement would
require the disclosure of material non-public information regarding Tetra
Tech and, accordingly, that the filing thereof, at the time requested, or the
offering of Tetra Tech Common Stock pursuant thereto, would materially and
adversely affect (i) a pending or scheduled public offering or private
placement of securities of Tetra Tech, (ii) an acquisition, merger,
consolidation or similar transaction by or of Tetra Tech, (iii) preexisting
and continuing negotiations, discussions or pending proposals with respect to
any of the foregoing transactions, or (iv) the financial condition of Tetra
Tech in view of the disclosure of any pending or threatened litigation,
claim, assessment or governmental investigation which might be required
thereby.


                                      3
<PAGE>

          In the event that Tetra Tech, in good faith, reasonably believes
that such conditions are continuing after such 90-day period, it may, with
the consent of the Holders of a majority of the Registrable Securities
subject (or to be subject) to the Registration Statement, which consent shall
not be unreasonably withheld, extend such 90-day period for an additional 30
days. Any further delay shall require the consent of the Holders of all such
shares which may be withheld in their sole discretion.

     3.   REGISTRATION PROCEDURES.  In connection with Tetra Tech's
registration obligations pursuant to SECTION 2 hereof, Tetra Tech will use
commercially reasonable efforts to effect such registration to permit the
sale of the Registrable Securities covered thereby in accordance with the
intended method or methods of disposition thereof, and pursuant thereto Tetra
Tech will as expeditiously as possible:

          (a)  prepare and file with the SEC a Registration Statement with
respect to such Registrable Securities and use its commercially reasonable
efforts to cause such Registration Statement to become effective; PROVIDED
that, before filing any Registration Statement or Prospectus or any
amendments or supplements thereto, Tetra Tech will furnish to the Holders of
the Registrable Securities covered by such Registration Statement and their
counsel, copies of all such documents proposed to be filed at least ten days
prior thereto, and Tetra Tech will not file any such Registration Statement
or amendment thereto or any Prospectus or any supplement thereto to which any
such Holder shall reasonably object within such ten day period; PROVIDED,
FURTHER, that Tetra Tech will not name or otherwise provide any information
with respect to any Holder in any Registration Statement or Prospectus
without the express written consent of such Holder, unless required to do so
by the Securities Act and the rules and regulations thereunder. The parties
will use their best efforts to resolve any objections under this SUBPARAGRAPH
(a);

          (b)  prepare and file with the SEC such amendments, post-effective
amendments and supplements to the Registration Statement and the Prospectus
as may be necessary to comply with the provisions of the Securities Act and
the rules and regulations thereunder with respect to the disposition of all
securities covered by such Registration Statement;

          (c)  notify the selling Holders (i) when the Prospectus or any
Prospectus supplement or post-effective amendment has been filed, and, with
respect to the Registration Statement or any post-effective amendment, when the
same has become effective, (ii) of any request by the SEC for amendments or
supplements to the Registration Statement or the Prospectus or for additional
information, (iii) of the issuance by the SEC of any stop order suspending the
effectiveness of the Registration Statement or the initiation of any proceedings
for that purpose, (iv) of the receipt by Tetra Tech of any notification with
respect to the suspension of the qualification of the Registrable Securities for
sale in any jurisdiction or the


                                      4
<PAGE>

initiation or threatening of any proceeding for such purpose and (v) of the
happening of any event which makes any statement made in the Registration
Statement, the Prospectus or any document incorporated therein by reference
untrue or which requires the making of any changes in the Registration
Statement, the Prospectus or any document incorporated therein by reference
in order to make the statements therein not misleading in light of the
circumstances then existing;

          (d)  make every commercially reasonable effort to obtain the
withdrawal of any order suspending the effectiveness of the Registration
Statement at the earliest possible moment;

          (e)  deliver to each selling Holder, without charge, such
reasonable number of conformed copies of the Registration Statement (and any
post-effective amendment thereto) and such number of copies of the Prospectus
(including each preliminary prospectus) and any amendment or supplement
thereto (and any documents incorporated by reference therein) as such Holder
may reasonably request. Tetra Tech consents to the use of the Prospectus or
any amendment or supplement thereto by each of the selling Holders in
connection with the offer and sale of the Registrable Securities covered by
the Prospectus or any amendment or supplement thereto;

          (f)  prior to any offering of Registrable Securities covered by a
Registration Statement, register or qualify or cooperate with the selling
Holders in connection with the registration or qualification of such
Registrable Securities for offer and sale under the securities or blue sky
laws of such jurisdictions as any such selling Holder reasonably requests,
and use commercially reasonable efforts to keep each such registration or
qualification effective, including through new filings, or amendments or
renewals, during the period such Registration Statement is required to be
kept effective pursuant to the terms of this Agreement; and do any and all
other acts or things necessary or advisable to enable the disposition in all
such jurisdictions reasonably requested by the Holders of the Registrable
Securities covered by such Registration Statement, PROVIDED that under no
circumstances shall Tetra Tech be required in connection therewith or as a
condition thereof to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions;

          (g)  cooperate with the selling Holders to facilitate the timely
preparation and delivery of certificates representing Registrable Securities
to be sold, free of any and all restrictive legends, such certificates to be
in such denominations and registered in such names as the Holders may request;

          (h)  upon the occurrence of any event contemplated by SECTION
3(c)(v) above, promptly prepare following the completion of all regulatory
requirements a supplement or post-effective amendment to the Registration
Statement or the Prospectus or any document incorporated therein by reference
or file any other required document so that, as thereafter delivered to the
purchasers of the Registrable Securities, the Prospectus will not contain an


                                      5
<PAGE>

untrue statement of a material fact or omit to state any material fact
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading;

          (i)  make generally available to the holders of Tetra Tech's
outstanding securities earnings statements satisfying the provisions of
Section 11(a) of the Securities Act, no later than 60 days after the end of
any 12 month period (or 90 days, if such period is a fiscal year) beginning
with the first month of Tetra Tech's first fiscal quarter commencing after
the effective date of the Registration Statement, which statements shall
cover said 12 month period;

          (j)  provide and cause to be maintained a transfer agent and
registrar for all Registrable Securities covered by each Registration
Statement from and after a date not later than the effective date of such
Registration Statement;

          (k)  use its best efforts to cause all Registrable Securities
covered by each Registration Statement to be listed, subject to notice of
issuance, prior to the date of the first sale of such Registrable Securities
pursuant to such Registration Statement, on each securities exchange on which
the Tetra Tech Common Stock is then listed, and admitted to trading on the
Nasdaq Stock Market, if the Tetra Tech Common Stock is then admitted to
trading on the Nasdaq Stock Market; and

          (l)  enter into such agreements and take such other actions as a
majority of the Holders shall reasonably request in order to expedite or
facilitate the disposition of such Registrable Securities.

     Each Holder agrees that, upon receipt of any notice from Tetra Tech of
the happening of any event of the kind described in SECTION 3(c)(v) hereof,
such Holder will forthwith discontinue disposition of Registrable Securities
under the Prospectus related to the applicable Registration Statement until
such Holder's receipt of the copies of the supplemented or amended Prospectus
contemplated by SECTION 3(h) hereof, or until it is advised in writing by
Tetra Tech that the use of the Prospectus may be resumed.

     It shall be a condition precedent to the obligations of Tetra Tech to
take any action pursuant to this SECTION 3 with respect to the Registrable
Securities of any selling Holder that such Holder shall furnish to Tetra Tech
such information regarding itself and the Registrable Securities held by it
as shall be required by the Securities Act to effect the registration of such
Holder's Registrable Securities.

     4.   REGISTRATION EXPENSES.  All expenses incident to any registration
to be effected hereunder and incident to Tetra Tech's performance of or
compliance with this Agreement, including without limitation all registration
and filing fees, fees and expenses of compliance with securities or blue sky
laws, printing expenses, messenger and delivery expenses, National
Association of Securities Dealers, Inc., stock exchange and qualification
fees, fees and


                                      6
<PAGE>

disbursements of Tetra Tech's counsel and of independent certified public
accountants of Tetra Tech (including the expenses of any special audit
required by or incident to such performance), the fees and disbursements of
one counsel and one accountant representing the Holders in such offering,
expenses of the underwriters that are customarily requested in similar
circumstances by such underwriters (excluding discounts, commissions or fees
of underwriters, selling brokers, dealer managers or similar securities
industry professionals relating to the distribution of the Registrable
Securities, which will be borne by the Holders), all such expenses being
herein called "Registration Expenses," will be borne by Tetra Tech. Tetra
Tech will also pay its internal expenses, the expense of any annual audit and
the fees and expenses of any person retained by Tetra Tech.

     5.   INDEMNIFICATION.

          (a)  INDEMNIFICATION BY TETRA TECH.  Tetra Tech agrees to indemnify
and hold harmless each Holder of Registrable Securities, its officers,
directors, partners and employees and each person who controls such Holder
(within the meaning of Section 15 of the Securities Act) from and against any
and all losses, claims, damages and liabilities (including any investigation,
legal or other expenses reasonably incurred in connection with, and any
amount paid in settlement of, any action, suit or proceeding or any claim
asserted) (collectively, "Damages") to which such Holder may become subject
under the Securities Act, the Exchange Act or other federal or state
securities law or regulation, at common law or otherwise, insofar as such
Damages arise out of or are based upon (i) any untrue statement or alleged
untrue statement of a material fact contained in any Registration Statement,
Prospectus or preliminary prospectus or any amendment or supplement thereto,
(ii) the omission or alleged omission to state therein a 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 and
(iii) any violation or alleged violation by Tetra Tech of the Securities Act,
the Exchange Act or any state securities or blue sky laws in connection with
the Registration Statement, Prospectus or preliminary prospectus or any
amendment or supplement thereto, PROVIDED that Tetra Tech will not be liable
to any Holder to the extent that such Damages arise from or are based upon
any untrue statement or omission (x) based upon written information furnished
to Tetra Tech by such Holder expressly for the inclusion in such Registration
Statement, (y) made in any preliminary prospectus if such Holder failed to
deliver a copy of the Prospectus with or prior to the delivery of written
confirmation of the sale by such Holder to the party asserting the claim
underlying such Damages and such Prospectus would have corrected such untrue
statement or omission and (z) made in any Prospectus if such untrue statement
or omission was corrected in an amendment or supplement to such Prospectus
and such Holder failed to deliver such amendment or supplement prior to or
concurrently with the sale of Registrable Securities to the party asserting
the claim underlying such Damages.

          (b)  INDEMNIFICATION BY HOLDER OF REGISTRABLE SECURITIES.  Each
Holder of Registrable Securities whose Registrable Securities are sold under
a Prospectus which is a part of


                                      7
<PAGE>

a Registration Statement agrees to indemnify and hold harmless Tetra Tech,
its directors and each officer who signed such Registration Statement and
each person who controls Tetra Tech (within the meaning of Section 15 of the
Securities Act), and each other Holder of Registrable Securities whose
Registrable Securities are sold under the Prospectus which is a part of such
Registration Statement (and such Holder's officers, directors and employees
and each person who controls such Holder within the meaning of Section 15 of
the Securities Act), under the same circumstances as the foregoing indemnity
from Tetra Tech to each Holder of Registrable Securities to the extent that
such losses, claims, damages, liabilities or actions arise out of or are
based upon any untrue statement of a material fact or omission of a material
fact that was made in the Prospectus, the Registration Statement, or any
amendment or supplement thereto, in reliance upon and in conformity with
information relating to such Holder furnished in writing to Tetra Tech by
such Holder expressly for use therein, PROVIDED that in no event shall the
aggregate liability of any selling Holder of Registrable Securities exceed
the amount of the net proceeds received by such Holder upon the sale of the
Registrable Securities giving rise to such indemnification obligation. Tetra
Tech and the selling Holders shall be entitled to receive indemnities from
underwriters, selling brokers, dealer managers and similar securities
industry professionals participating in the distribution, to the same extent
as customarily furnished by such persons in similar circumstances.

          (c)  CONDUCT OF INDEMNIFICATION PROCEEDINGS.  Any person entitled
to indemnification hereunder will (i) give prompt notice to the indemnifying
party of any claim with respect to which it seeks indemnification and (ii)
permit such indemnifying party to assume the defense of such claim with
counsel reasonably satisfactory to the indemnified party; PROVIDED, HOWEVER,
that any person entitled to indemnification hereunder shall have the right to
employ separate counsel and to participate in the defense of such claim, but
the fees and expenses of such counsel shall be at the expense of such person
and not of the indemnifying party unless (A) the indemnifying party has
agreed to pay such fees or expenses, (B) the indemnifying party shall have
failed to assume the defense of such claim and employ counsel reasonably
satisfactory to such person or (C) in the reasonable judgment of such person
and the indemnifying party, based upon advice of their respective counsel, a
conflict of interest may exist between such person and the indemnifying party
with respect to such claims (in which case, if the person notifies the
indemnifying party in writing that such person elects to employ separate
counsel at the expense of the indemnifying party, the indemnifying party
shall not have the right to assume the defense of such claim on behalf of
such person). If such defense is not assumed by the indemnifying party, the
indemnifying party will not be subject to any liability for any settlement
made without its consent (but such consent will not be unreasonably
withheld). No indemnified party will be required to consent to entry of any
judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by all claimants or plaintiffs to such
indemnified party of a release from all liability in respect to such claim or
litigation. Any indemnifying party who is not entitled to, or elects not to,
assume the defense of a claim will not be obligated to pay the fees and
expenses of more than one counsel for all parties indemnified by such
indemnifying party with respect to such claim. As used in this SECTION 5(c),


                                      8
<PAGE>

the terms "indemnifying party", "indemnified party" and other terms of
similar import are intended to include only Tetra Tech (and its officers,
directors and control persons as set forth above) on the one hand, and the
Holders (and their officers, directors, partners, employees, attorneys and
control persons as set forth above) on the other hand, as applicable.

          (d)  CONTRIBUTION.  If for any reason the foregoing indemnity is
unavailable, then the indemnifying party shall contribute to the amount paid
or payable by the indemnified party as a result of such losses, claims,
damages, liabilities or expenses (i) in such proportion as is appropriate to
reflect the relative fault of the indemnifying party and the indemnified
party in connection with the statements or omissions which resulted in such
losses, claims, damages, liabilities or expenses, as well as any other
relevant equitable considerations. The relative fault of such indemnifying
party and indemnified party shall be determined by reference to, among other
things, whether the untrue statement or alleged untrue statement of a
material fact or omission or alleged omission to state a material fact
relates to information supplied by such indemnifying party or by such
indemnified party, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The parties acknowledge and agree that it would not be just and equitable if
contribution pursuant to this SECTION 5(d) were determined by pro rata
allocation or by any other method of allocation which does not take into
account the equitable considerations referred to in this SECTION 5(d).
Notwithstanding the foregoing, no Holder shall be required to contribute any
amount in excess of the amount such Holder would have been required to pay to
an indemnified party if the indemnity under SECTION 5(b) hereof was
available. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The obligation of any person to contribute pursuant to
this SECTION 5(d) shall be several and not joint.

          (e)  TIMING OF PAYMENTS.  An indemnifying party shall make payments
of all amounts required to be made pursuant to the foregoing provisions of
this SECTION 5 to or for the account of the indemnified party from time to
time promptly upon receipt of bills or invoices relating thereto or when
otherwise due or payable.

          (f)  SURVIVAL.  The indemnity and contribution agreements contained
in this SECTION 5 shall remain in full force and effect, regardless of any
investigation made by or on behalf of Tetra Tech, a participating Holder, its
officers, directors, partners, attorneys, agents or any person, if any, who
controls Tetra Tech or such Holder as aforesaid, and shall survive the
transfer of such Registrable Securities by such Holder.

     6.   PREPARATION; REASONABLE INVESTIGATION.  In connection with the
preparation and filing of a Registration Statement pursuant to the terms of
this Agreement:

          (a)  Tetra Tech shall, with respect to a Registration Statement filed
pursuant to SECTION 2, give the Holders of such Registrable Securities so
registered, their underwriters, if any,


                                      9
<PAGE>

and their respective counsel and accountants the opportunity to participate
in the preparation of such Registration Statement (other than reports and
proxy statements incorporated therein by reference and properly filed with
the SEC) and each Prospectus included therein or filed with the SEC, and each
amendment thereof or supplement thereto; and

          (b)  Tetra Tech shall give the Holders of such Registrable
Securities so registered, their underwriters, if any, and their respective
counsel and accountants such reasonable access to its books and records and
such opportunities to discuss the business of Tetra Tech with its officers
and the independent public accountants who have certified its financial
statements as shall be necessary, in the opinion of such Holders or such
underwriters, to conduct a reasonable investigation within the meaning of
Section 11(b)(3) of the Securities Act.

     7.   REPRESENTATIONS.  Tetra Tech represents and warrants to, and agrees
with, the Holders that:

          (a)  The Registration Statement and the Prospectus, when it becomes
effective or is filed with the SEC, will conform in all material respects to the
requirements of the Securities Act and will not contain an untrue statement of a
material fact or omit to state a material fact required to be stated or
necessary to make the statements not misleading in light of the circumstances
then existing.

          (b)  At all times subsequent to the effective date of the
Registration Statement, when a Prospectus would be required to be delivered
under the Securities Act, the Registration Statement and the Prospectus, as
then amended or supplemented, will conform in all material respects to the
requirements of the Securities Act and will not contain an untrue statement
of a material fact or omit to state a material fact required to be stated or
necessary to make the statements not misleading in light of the circumstances
then existing.

          (c)  Any documents incorporated by reference in the Prospectus,
when they become or became effective or are or were filed with the SEC, as
the case may be, will conform or be conformed in all material aspects to the
requirements of the Securities Act or the Exchange Act, as applicable, and
none of such documents will contain or contained an untrue statement of a
material fact or will admit or omitted to state a material fact required to
be stated or necessary to make the statements therein not misleading in light
of the circumstances then existing.

          (d)  The above representations and warranties shall not apply to
any statements or omissions made in reliance upon and in conformity with
information furnished in writing to Tetra Tech by a Holder expressly for use
in the Registration Statement or the Prospectus.

     8.   RULE 144.  Tetra Tech covenants that it will use commercially
reasonable efforts to file, on a timely basis, the reports required to be
filed by it under the Securities Act and the Exchange Act and the rules and
regulations adopted by the SEC thereunder, and it will take such


                                      10
<PAGE>

further action as any Holder may reasonably request (including, without
limitation, compliance with the current public information requirements of
Rule 144(c) and Rule 144A), all to the extent required from time to time to
enable such Holder to sell Registrable Securities without registration under
the Securities Act within the limitation of the conditions provided by Rule
144, Rule 144A or any similar rule or regulation hereafter adopted by the
SEC. Upon the request of any Holder, Tetra Tech will promptly deliver to such
Holder a written statement verifying that it has complied with such
information and requirements.

     9.   SPECIFIC PERFORMANCE.  Each Holder, in addition to being entitled
to exercise all rights provided herein or granted by law, including recovery
of damages, will be entitled to specific performance of its rights under this
Agreement. Tetra Tech agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the
provisions of this Agreement and hereby agrees to waive the defense in any
action for specific performance that a remedy at law would be adequate.

     10.  NOTICES.  All notices and other communications required or
permitted hereunder shall be in writing and shall be mailed by United States
first-class mail, postage prepaid, sent by facsimile or delivered personally
by hand or nationally recognized courier addressed (a) if to a Holder, as
indicated on the list of Holders attached hereto as SCHEDULE A, or at such
other address as such Holder or permitted assignee shall have furnished to
Tetra Tech in writing, with a copy to Dowling, Aaron & Keeler, 6051 N. Fresno
Street, Suite 200, Fresno, California 93710-5280, Attention: Christopher A.
Brown, Esq.; Facsimile (559) 432-4590, or (b) if to Tetra Tech, at such
address or facsimile number as Tetra Tech shall have furnished to each Holder
in writing. All such notices and other written communications shall be
effective on the date of mailing, facsimile transfer or delivery.

     11.  SUCCESSORS AND ASSIGNS: ASSIGNMENT OF RIGHTS.  The rights and
benefits of a Holder hereunder may not be assigned to a transferee or
assignee without the consent of Tetra Tech; PROVIDED, HOWEVER, that, no later
than the 10th day prior to the filing of the Registration Statement under
SECTION 2 hereof, the rights and benefits of a Holder hereunder may be
transferred in connection with a transfer or assignment of any Registrable
Securities held by such Holder (i) by gift to immediate family members of
such Holder, or trusts or other entities for the sole benefit thereof, or
(ii) by gift to any entity in which such Holder, his or her immediate family
members, or trusts or other entities for the sole benefit thereof
beneficially own all of the voting securities; PROVIDED, HOWEVER, that in
each case, the transferee executes an instrument pursuant to which the
transferee agrees to be bound by the terms and conditions hereof as a Holder,
and such other documents as Tetra Tech or its counsel may reasonably require,
after which, such transferee shall be deemed a "Holder" hereunder. Any
transfer of Registrable Securities, and rights hereunder, shall be subject to
compliance with applicable securities laws and the restrictions contained in
the Investment Letter executed by each Holder pursuant to the Reorganization
Agreement.


                                      11
<PAGE>

     12.  SEVERABILITY.  In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability
of any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

     13.  ENTIRE AGREEMENT; AMENDMENT; WAIVER.  This Agreement, the
Reorganization Agreement and the other agreements contemplated thereby
constitute the full and entire understanding and agreement among the parties
with regard to the subjects hereof and thereof. Without limiting the
foregoing, the rights of the Holders to registration pursuant to the terms of
this Agreement shall be subject to the limitations on resale contained in the
Investment Letter (as defined in the Reorganization Agreement). Neither this
Agreement nor any term hereof may be amended, waived, discharged or
terminated, except by a written instrument signed by Tetra Tech and the
holders of at least 51% of the Registrable Securities and any such amendment,
waiver, discharge or termination shall be binding upon all the parties
hereto, but in no event shall the obligation of any party hereto be
materially increased, except upon the written consent of such party.

     14.  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be original, and all of which together
shall constitute one instrument.

     15.  GOVERNING LAW.  This Agreement shall be governed by, and construed
in accordance with, the laws of the State of California without giving effect
to principles of conflicts of laws thereof.

     16.  NO THIRD PARTY BENEFICIARIES.  The covenants and agreements set
forth herein are for the sole and exclusive benefit of the parties hereto and
their respective successors and assigns and such covenants and agreements
shall not be construed as conferring, and are not intended to confer, any
rights or benefits upon any other persons.


                                      12
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.


                                      TETRA TECH, INC.

                                      By: /s/ Li-San Hwang
                                         ----------------------------------
                                         Li-San Hwang
                                         Chairman, Chief Executive Officer
                                         and President


                                      HOLDERS:

                                      Kenneth L. Shelton

                                      Lonny B. Cunningham


                                      13
<PAGE>

                                                                     SCHEDULE A


                               SCHEDULE OF HOLDERS

<TABLE>
<CAPTION>
                                             Number of Shares of Tetra Tech
                                             Common Stock Issued Pursuant
Holder's Name/Address/Facsimile No.          to the Reorganization Agreement
- -----------------------------------          --------------------------------
<S>                                          <C>
Kenneth L. Shelton                                    88,275 shares
Utilities & C.C., Inc.
1555 Bedell Court
Roseville, California 95747
Facsimile: (916) 773-9394

Lonny B. Cunningham                                   49,655 shares
Utilities & C.C., Inc.
1555 Bedell Court
Roseville, California 95747
Facsimile: (916) 773-9394

</TABLE>


                                      14

<PAGE>

<TABLE>
<CAPTION>

                                                                                                      Exhibit 11

                                                 Tetra Tech, Inc.
                                  Computation of Net Income Per Common Share
                                                   (Unaudited)


                                                      Three Months Ended                  Nine Months Ended
                                               --------------------------------------------------------------------
                                                   July 4,          June 28,          July 4,          June 28,
                                                    1999              1998             1999              1998
                                               ---------------  ----------------  ---------------  ----------------
<S>                                            <C>              <C>               <C>              <C>
Basic:
   Common stock outstanding, beginning
     of period............................         37,578,160       35,061,500        35,788,250        32,366,022
   Exchanged stock........................              5,891               --           143,382
   Stock options exercised................             73,205          140,773           243,943           244,452
   Stock purchase plan issuance...........            156,170          143,922           156,361           143,922
   Issuance of common stock...............            364,312               --         1,845,802         2,502,197
   Payment of fractional shares...........            (45,720)              --           (45,720)             (398)
                                               ---------------  ----------------  ---------------  ----------------

   Common stock outstanding, end
     of period............................         38,132,018       35,346,195        38,132,018        35,346,195
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

   Weighted average common stock
     outstanding during the period........         37,801,477       35,183,614        36,805,123        34,695,200
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

   Net income as reported in condensed
     consolidated financial statements....     $    8,503,000   $    5,493,000    $   20,392,000   $    14,064,000
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

   Basic Earnings Per Share...............     $         0.22   $         0.16    $         0.55   $          0.41
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

Diluted:
   Weighted average common stock
     outstanding during the period........         37,801,477       35,183,614        36,805,123        34,695,200

   Potential common shares under the
     treasury stock method assuming the
     exercise of options and warrants and
     the conversion of preferred stock and
     exchangeable stock of a subsidiary...          2,343,811        1,318,002         2,460,748         1,549,587
                                               ---------------  ----------------  ---------------  ----------------

         Total............................         40,145,288       36,501,616        39,265,871        36,244,787
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

   Net income as reported in condensed
     consolidated financial statements....     $    8,503,000   $    5,493,000    $   20,392,000   $    14,064,000
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------

   Diluted Earnings Per Share.............     $         0.21   $         0.15    $         0.52   $          0.39
                                               ---------------  ----------------  ---------------  ----------------
                                               ---------------  ----------------  ---------------  ----------------
</TABLE>

   See accompanying Notes to the Condensed Consolidated Financial Statements.

<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5

<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          OCT-03-1999
<PERIOD-START>                             OCT-04-1998
<PERIOD-END>                               JUL-04-1999
<CASH>                                           9,293
<SECURITIES>                                         0
<RECEIVABLES>                                  156,942
<ALLOWANCES>                                     7,279
<INVENTORY>                                          0
<CURRENT-ASSETS>                               171,949
<PP&E>                                          36,881
<DEPRECIATION>                                  18,578
<TOTAL-ASSETS>                                 345,028
<CURRENT-LIABILITIES>                           87,971
<BONDS>                                              0
                                0
                                          0
<COMMON>                                           381
<OTHER-SE>                                     221,340
<TOTAL-LIABILITY-AND-EQUITY>                   345,028
<SALES>                                        157,091
<TOTAL-REVENUES>                               157,091
<CGS>                                          124,541
<TOTAL-COSTS>                                  124,541
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                                 649
<INCOME-PRETAX>                                 15,049
<INCOME-TAX>                                     6,546
<INCOME-CONTINUING>                              8,503
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                     8,503
<EPS-BASIC>                                       0.22
<EPS-DILUTED>                                     0.21


</TABLE>


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