TETRA TECH INC
8-K, 1998-10-01
ENGINEERING SERVICES
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                       SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549



                                    Form 8-K

               Current Report Pursuant to Section 13 or 15(d) of
                           The Securities Act of 1934



     Date of Report (Date of earliest event reported)  September 22, 1998
                                                     ----------------------
                                Tetra Tech, Inc.

     ----------------------------------------------------------------------
             (Exact name of registrant as specified in its charter)


                Delaware            0-19655            95-4148514
     ----------------------------------------------------------------------
             State or other       (Commission       (I.R.S. Employer
              jurisdiction        File Number)    Identification No.)


          670 N. Rosemead Boulevard, Pasadena, California  91107-2190
     ----------------------------------------------------------------------
           (Address of principle executive offices)        (Zip Code)

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

                                 Not applicable
     ----------------------------------------------------------------------
         (Former name or former address if changed since last report.)

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ITEM 2.   ACQUISITION OR DISPOSITION OF ASSETS.

          (a)  On September 22, 1998, the Registrant completed the acquisition
of 1056584 Ontario Limited, an Ontario corporation, 1056585 Ontario Limited, an
Ontario corporation, Cen-Comm Communications Inc., an Ontario corporation,
Sentrex Electronics Inc., an Ontario corporation, Venture Cable Ltd., an Ontario
corporation and LAL Corp., a Delaware corporation (collectively, the "Sentrex
Companies"), pursuant to the terms of a Stock Purchase Agreement dated as of
September 22, 1998 (the "Agreement") among the Registrant, Tetra Tech Canada, an
Ontario corporation and wholly-owned subsidiary of the Registrant ("TTC"), and
the shareholders of the Sentrex Companies (collectively, the "Shareholders").
The Agreement provided for the purchase by TTC of all of the outstanding shares
of capital stock of the Sentrex Companies from the Shareholders (the "Share
Purchase").

          In connection with the Share Purchase, the Shareholders received
aggregate consideration in the amount of $22,646,441 U.S. Dollars, which was
paid by TTC as follows:

               (i)  TTC issued to the Shareholders an aggregate of 920,354 of
its exchangeable shares (the "TTC Exchangeable Shares").  For purposes of the
Agreement, each TTC Exchangeable Share was valued at $19.70, for an aggregate
value of $18,130,973.80.  Each TTC Exchangeable Share is exchangeable,
commencing on February 22, 1999, for one share of the common stock, $.01 par
value ("Common Stock"), of the Registrant.

               (ii) TTC paid to the Stockholders cash in the aggregate amount of
$4,515,467.20.

          In determining the consideration to be paid in the Share Purchase, the
Registrant investigated the Sentrex Companies and their businesses and
determined an approximate aggregate value of the Sentrex Companies to the
Registrant based on investment factors including the book value of the Sentrex
Companies' assets, an appropriate multiple of the Sentrex Companies' current and
future earnings, the Sentrex Companies' backlog and current contracts, the
Sentrex Companies' revenues, the Sentrex Companies' reputation in the field of
design, construction and maintenance of communication and information transport
systems, including fiber optic cable, coaxial cable, microwave and personal
communication systems, and the compatibility of the Sentrex Companies'
geographic scope and technical capabilities.  A final determination of such
value was arrived at by means of arm's length bargaining among the parties to
the Agreement.

          There was no material relationship between the Sentrex Companies
(including their officers, directors and stockholders) and Registrant or any of
its affiliates, or any director or officer of the Registrant, or any associate
of any such officer or director, other than as described below.
                                       2.
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          In February 1998, the Registrant's wholly-owned subsidiary, Whalen
Service Corps Inc., a Delaware corporation ("WSC"), and one of the Sentrex
Companies, LAL Corp., a Delaware corporation ("LAL"), formed Whalen/Sentrex LLC,
a California limited liability company ("Whalen/Sentrex").  Whalen/Sentrex was
formed to engage in the business of providing project management, construction
management and technical services to the U.S. cable television industry.  At the
time of the Share Purchase, WSC and LAL held 52% and 48% membership interests in
Whalen/Sentrex, respectively.  The Registrant will continue to operate the
business of Whalen/Sentrex following the Share Purchase.

          In order to fund, in part, the cash payment made to the Shareholders
in connection with the Merger, the Registrant drew on its line of credit with
Bank of America National Trust and Savings Association (the "Lender") pursuant
to the terms of that certain Credit Agreement dated as of September 15, 1995, as
amended, between the Registrant and the Lender.

          (b)  At the time of the Share Purchase, the Sentrex Companies were
engaged in the business of providing design, construction and maintenance of
communication and information transport systems, including fiber optic cable,
coaxial cable, microwave and personal communication systems.  The Registrant
intends to continue to engage in such business.


ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS.

          (a)  FINANCIAL STATEMENTS OF BUSINESSES ACQUIRED.

          The Registrant is not required to provide financial statements of the
businesses acquired pursuant to Rule 3-05 of Regulation S-X.

          (b)  PRO FORMA FINANCIAL INFORMATION.

          The Registrant is not required to provide pro forma financial
information with respect to the Share Purchase that would be required pursuant
to Article 11 of Regulation S-X.
                                       3.
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          (c)  EXHIBITS.

          2.1* Stock Purchase Agreement dated as of September 22, 1998 by and
               among Tetra Tech, Inc., Tetra Tech Canada Ltd. and the
               Stockholders of the Sentrex Companies named therein.


________________

*    The Schedules to Exhibit 2.1 have not been filed with the Commission
     because the Registrant believes that such Schedules do not contain
     information which is material to an investment decision.  A list of such
     Schedules is set forth on page v. of Exhibit 2.1.  The Registrant hereby
     agrees to furnish supplementally a copy of the omitted Schedules to the
     Commission upon request.
                                       4.
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                                   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 hereunto duly authorized.

          Date:  September 30, 1998


                                        TETRA TECH, INC.


                                        By:  ____________________________
                                             James M. Jaska
                                             Vice President and
                                             Chief Financial Officer
                                       5.




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                                                                EXHIBIT 2.1









                            STOCK PURCHASE AGREEMENT

                                     AMONG

                               TETRA TECH, INC.,
                             TETRA TECH CANADA LTD.

                                      AND

                         THE SHAREHOLDERS NAMED HEREIN





                               September 22, 1998
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                               TABLE OF CONTENTS
                                                                      Page
                                                                     ------
ARTICLE 1 SALE AND PURCHASE OF SHARES  .  .  .  .  .  .  .  .  .  .  .  2

  1.1  SALE AND PURCHASE OF THE SHARES .  .  .  .  .  .  .  .  .  .  .  2
  1.2  CONSIDERATION .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  2
  1.3  FURTHER ASSURANCES  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  2

ARTICLE 2 JOINT REPRESENTATIONS AND WARRANTIES
          OF THE SHAREHOLDERS .  .  .  .  .  .  .  .  .  .  .  .  .  .  3

  2.1  ORGANIZATION AND GOOD STANDING  .  .  .  .  .  .  .  .  .  .  .  3
  2.2  INVESTMENTS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  3
  2.3  CAPITAL STRUCTURE   .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  3
  2.4  TAXES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  4
  2.5  TRANSACTIONS WITH AFFILIATES.  .  .  .  .  .  .  .  .  .  .  .   5
  2.6  FINANCIAL STATEMENTS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  6
  2.7  TITLE TO PROPERTIES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  6
  2.8  REAL PROPERTY.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .   6
  2.9  LEASES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .   6
  2.10 FIXED ASSETS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .   6
  2.11 INTANGIBLE PERSONAL PROPERTY.  .  .  .  .  .  .  .  .  .  .  .   7
  2.12 ACCOUNTS RECEIVABLE.  .  .  .  .  .  .  .  .  .  .  .  .  .  .   7
  2.13 LICENSES AND PERMITS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  7
  2.14 INSURANCE  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  7
  2.15 ABSENCE OF CERTAIN CHANGES.  .  .  .  .  .  .  .  .  .  .  .  .  8
  2.16 COMPLIANCE WITH CONTRACTS .  .  .  .  .  .  .  .  .  .  .  .  .  9
  2.17 COMPLIANCE WITH LAWS.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10
  2.18 NO UNDISCLOSED LIABILITIES   .  .  .  .  .  .  .  .  .  .  .  . 10
  2.19 EMPLOYEES  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10
  2.20 LITIGATION    .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11
  2.21 ENVIRONMENTAL COMPLIANCE  .  .  .  .  .  .  .  .  .  .  .  .  . 12
  2.22 EMPLOYEE BENEFITS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 13
  2.23 BANK ACCOUNTS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15
  2.24 INVENTORY  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15
  2.25 CORPORATE RECORDS   .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15
  2.26 ACCOUNTING RECORDS  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 15
  2.27 BROKERS AND FINDERS .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16
  2.28 ACCURACY OF REPRESENTATIONS AND WARRANTIES  .  .  .  .  .  .  . 16

ARTICLE 3 REPRESENTATIONS AND WARRANTIES OF EACH SHAREHOLDER.  .  .  . 16

  3.1  TITLE TO SHARES  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 16
  3.2  AUTHORIZATION AND APPROVALS  .  .  .  .  .  .  .  .  .  .  .  . 16
  3.3  NO VIOLATIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 17
  3.4  SECURITIES LAW MATTERS .  .  .  .  .  .  .  .  .  .  .  .  .  . 17
  3.5  RESIDENCY  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18
                                       i.

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                         TABLE OF CONTENTS (Continued)
                                                                      Page
                                                                     ------
ARTICLE 4 REPRESENTATIONS AND WARRANTIES
          OF TETRA TECH .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18

  4.1  ORGANIZATION AND POWER; FOREIGN QUALIFICATION  .  .  .  .  .  . 18
  4.2  CAPITAL STRUCTURE.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 18
  4.3  AUTHORIZATION AND APPROVALS  .  .  .  .  .  .  .  .  .  .  .  . 18
  4.4  NO CONFLICTS  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 19
  4.5  FINANCIAL STATEMENTS AND SEC REPORTS  .  .  .  .  .  .  .  .  . 19
  4.6  BROKERS AND FINDERS .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 20
  4.7  NO MATERIAL ADVERSE CHANGES  .  .  .  .  .  .  .  .  .  .  .  . 20
  4.8  ACCURACY OF REPRESENTATIONS AND WARRANTIES     .  .  .  .  .  . 20

ARTICLE 5 COVENANTS.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .20

  5.1  TAXES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 20
  5.2  STOCK OPTIONS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 22
  5.3  ELECTION UNDER SUBSECTION 85(1) OF THE
       INCOME TAX ACT (CANADA).  .  .  .  .  .  .  .  .  .  .  .  .  . 22

ARTICLE 6 CLOSING .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 23

  6.1  THE CLOSING.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 23
  6.2  CLOSING DELIVERIES  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 23
  6.3  FURTHER ACTS  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 24

ARTICLE 7 SURVIVAL OF REPRESENTATIONS, WARRANTIES COVENANTS
          AND RELATED AGREEMENTS; INDEMNIFICATION.  .  .  .  .  .  .  .25

  7.1  GENERAL LIABILITY PERIOD  .  .  .  .  .  .  .  .  .  .  .  .  . 25
  7.2  TAX LIABILITY PERIOD.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 25
  7.3  SURVIVAL OF THE TETRA TECH'S AND TTC'S OBLIGATIONS.  .  .  .  . 25
  7.4  INDEMNITY BY THE SHAREHOLDERS.  .  .  .  .  .  .  .  .  .  .  . 25
  7.5  INDEMNITY BY THE PURCHASER.  .  .  .  .  .  .  .  .  .  .  .  . 26
  7.6  LIMITATIONS ON RECOVERABLE LOSSES  .  .  .  .  .  .  .  .  .  . 26
  7.7  CLAIMS FOR INDEMNIFICATION; DISPUTES  .  .  .  .  .  .  .  .  . 27
  7.8  INDEMNITY AS EXCLUSIVE REMEDY.  .  .  .  .  .  .  .  .  .  .  . 28
  7.9  ASSIGNMENT OF CLAIMS.  .  .  .  .  .  .  .  .  .  .  .  .  .  . 28

ARTICLE 8 GENERAL PROVISIONS  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29

  8.1  ENTIRE AGREEMENT; MODIFICATIONS; WAIVER  .  .  .  .  .  .  .  . 29
  8.2  SEVERABILITY  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
  8.3  SUCCESSORS AND ASSIGNS .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
  8.4  COUNTERPARTS  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
  8.5  GOVERNING LAW .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
  8.6  NOTICES .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
  8.7  EXPENSES.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 30
  8.8  CONFIDENTIALITY  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 30
                                      ii.
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                         TABLE OF CONTENTS (Continued)
                                                                      Page
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  8.9  TIME .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 31
  8.10 NO THIRD PARTIES BENEFITTED  .  .  .  .  .  .  .  .  .  .  .  . 31
  8.11 RECITALS, SCHEDULES AND EXHIBITS.  .  .  .  .  .  .  .  .  .  . 31
  8.12 SECTION HEADINGS .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 31
  8.13 SHAREHOLDERS' AGENT .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 31
  8.14 DOLLAR REFERENCES   .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 32
                                      iii.
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                                 EXHIBIT INDEX


Exhibit 1.2A        Rights of TTC Exchangeable Shares

Exhibit 1.2B        Support Agreement

Exhibit 1.2C        Consideration to be Received by the Shareholders

Exhibit 6.2A        Opinion of Lipman, Zener &Waxman

Exhibit 6.2B        Opinion of Hodgson, Russ, Andrews, Woods & Goodyear LLP

Exhibit 6.2C        Employment and Noncompetition Agreement

Exhibit 6.2D        Registration Rights Agreement

Exhibit 6.2E        Opinion of Riordan & McKinzie

Exhibit 6.2F        Opinion of McCarthy Tetrault
                                      iv.
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                                 SCHEDULE INDEX


Schedule 2.1        Foreign Qualification

Schedule 2.2        Investments

Schedule 2.3        Capital Structure

Schedule 2.4        Tax Matters

Schedule 2.5        Affiliate Transactions

Schedule 2.6        Financial Statements

Schedule 2.7        Liens

Schedule 2.9        Leases

Schedule 2.10       Fixed Assets

Schedule 2.11       Intangible Personal Property

Schedule 2.12       Accounts Receivable

Schedule 2.13       Licenses and Permits

Schedule 2.14       Insurance

Schedule 2.15       Changes

Schedule 2.16       Contracts

Schedule 2.17       Compliance with Laws

Schedule 2.18       Liabilities

Schedule 2.19       Employees

Schedule 2.20       Litigation

Schedule 2.22       Employee Benefits

Schedule 2.23       Bank Accounts
                                       v.
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                            STOCK PURCHASE AGREEMENT


     THIS STOCK PURCHASE AGREEMENT (the "Agreement") is entered into as of
September 22, 1998 by and among Tetra Tech, Inc., a Delaware corporation ("Tetra
Tech"),  Tetra Tech Canada Ltd., an Ontario corporation and wholly-owned
subsidiary of Tetra Tech ("TTC"), and the shareholders (collectively, the
"Shareholders") of 1056584 Ontario Limited, an Ontario corporation ("1056584
Ltd."), 1056585 Ontario Limited, an Ontario corporation ("1056585 Ltd."), Cen-
Comm Communications Inc., an Ontario corporation ("CCC"), Sentrex Electronics
Inc., an Ontario corporation ("SEI"), Venture Cable Ltd., an Ontario corporation
("VCL"), and LAL Corp., a Delaware corporation ("LAL") (1056584 Ltd., 1056585
Ltd., CCC, SEI, VCL and LAL are hereinafter referred to individually as a
"Sentrex Company" and collectively as the "Sentrex Companies"), listed on the
signature pages to this Agreement.


                                R E C I T A L S

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of 1056584 Ltd. (the "1056584 Shares"), and such Shareholders
desire to sell the 1056584 Shares to TTC upon the terms and conditions set forth
herein;

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of 1056585 Ltd. (the "1056585 Shares"), and such Shareholders
desire to sell the 1056585 Shares to TTC upon the terms and conditions set forth
herein;

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of CCC (the "CCC Shares"), and such Shareholders desire to sell
the CCC Shares to TTC upon the terms and conditions set forth herein;

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of SEI (the "SEI Shares"), and such Shareholders desire to sell
the SEI Shares to TTC upon the terms and conditions set forth herein;

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of VCL (the "VCL Shares"), and such Shareholders desire to sell
the VCL Shares to TTC upon the terms and conditions set forth herein;

     WHEREAS, certain Shareholders own 100% of the issued and outstanding shares
of capital stock of LAL (the "LAL Shares"), and such Shareholders desire to sell
the LAL Shares to TTC upon the terms and conditions set forth herein;

     WHEREAS, TTC desire to purchase the 1056584 Shares, the 1056585 Shares, the
CCC Shares, the SEI Shares, the VCL Shares and the LAL Shares (collectively
referred to as the "Shares") upon the terms and conditions set forth herein;
<PAGE>
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     NOW, THEREFORE, Tetra Tech, TTC and the Shareholders, in consideration of
the agreements and covenants contained herein and subject to the satisfaction of
the conditions set forth herein, hereby make the following representations and
warranties, give the following covenants and agree as follows:


                                   ARTICLE 1

                          SALE AND PURCHASE OF SHARES

     1.1  SALE AND PURCHASE OF THE SHARES.  Subject to the terms and conditions
set forth in this Agreement and on the basis of and in reliance upon the
representations, warranties, obligations, covenants and agreements set forth in
this Agreement, the Shareholders shall sell, assign, transfer, convey and
deliver to TTC, and TTC shall purchase, acquire and accept, the Shares.

     1.2  CONSIDERATION.

          (a)  The total price to be paid by TTC to the Shareholders for the
Shares shall be $22,646,441 U.S. Dollars (the "Purchase Price").  Of such
amount, $4,515,467.20 shall be paid in cash on the Closing Date (as defined in
SECTION 6.1 hereof) by wire transfer of immediately available funds.  The
balance of the Purchase Price for the Shares shall be paid in exchangeable
shares of TTC (the "TTC Exchangeable Shares"), having the rights, privileges,
restrictions and conditions set forth in EXHIBIT 1.2A attached hereto (the
"Exchangeable Share Provisions") and a value per share equal to the Average
Price (as defined below).  Each of the TTC Exchangeable Shares is exchangeable
for one share of the common stock, $.01 par value, of Tetra Tech ("Tetra Tech
Common Stock") pursuant to the terms of the Exchangeable Share Provisions and
the Support Agreement attached hereto as EXHIBIT 1.2B.

          (b)  For purposes of the share exchange described in SUBPARAGRAPH (a)
above, the value of one share of Tetra Tech Common Stock shall be $19.70 (the
"Average Price").  No fractional share of Tetra Tech Common Stock will be issued
in exchange for the TTC Exchangeable Shares, but, in lieu thereof, each
Shareholder who would otherwise be entitled to a fraction of a share of Tetra
Tech Common Stock will be entitled to receive from Tetra Tech an amount of cash
(rounded to the nearest whole cent) equal to the product of (a) the fraction
multiplied by (b) the Average Price.

          (c)  The consideration to be received by each Shareholder on the
Closing Date, consisting of cash and TTC Exchangeable Shares, shall be as set
forth in EXHIBIT 1.2C attached hereto.

     1.3  FURTHER ASSURANCES.  The parties shall, at any time and from time to
time after the Closing, upon the written request of the other party and at the
sole cost and expense of the other party, do, execute, acknowledge and deliver,
and cause to be done, executed,
                                       2.
<PAGE>
<PAGE>
acknowledged or delivered, all such further acts, deeds, assignments, transfers,
conveyances, powers of attorney or assurances as may be reasonably required to
effectuate fully the intent and purposes of this Agreement.


                                   ARTICLE 2

                      JOINT REPRESENTATIONS AND WARRANTIES
                              OF THE SHAREHOLDERS

     The Shareholders, jointly and severally, represent and warrant to Tetra
Tech and TTC as follows:

     2.1  ORGANIZATION AND GOOD STANDING.  Each Sentrex Company and each of its
subsidiaries (individually, a "Subsidiary" and collectively, the
"Subsidiaries"), is a corporation duly organized, validly existing and in good
standing under the laws of the jurisdiction of its incorporation.  Except as set
forth on SCHEDULE 2.1, the Company and each Subsidiary is duly qualified to
transact business and is in good standing in every jurisdiction in which the
character of its business makes such qualification necessary, all of which
jurisdictions are listed on SCHEDULE 2.1 attached hereto.  Each Sentrex Company
and each Subsidiary has all necessary power and authority to carry on its
business as it is now being conducted, and to own or lease and operate its
properties and assets.

     2.2  INVESTMENTS.  Except as set forth on SCHEDULE 2.2 attached hereto, no
Sentrex Company, directly or indirectly, owns or controls any interest or
investment (whether equity or debt) in any corporation, partnership, joint
venture, business organization, trust or other entity.

     2.3  CAPITAL STRUCTURE.  The authorized capital stock of each Sentrex
Company is as set forth on SCHEDULE 2.3 attached hereto, and all outstanding
shares of each Sentrex Company are owned of record and beneficially as set forth
on SCHEDULE 2.3.  Except for any of the transactions contemplated pursuant to
this Agreement and as set forth on SCHEDULE 2.3, there are no outstanding
options, warrants, convertible debt or securities, calls, agreements,
arrangements, commitments, understandings or other rights to purchase any
Sentrex Company's capital stock, or any Subsidiary's capital stock or securities
convertible into or exchangeable for any such capital stock.  All of such shares
have been issued in transactions exempt from registration and prospectus
requirements under applicable Canadian securities laws and the Securities Act of
1933, as amended (the "Securities Act"), and no Sentrex Company has violated
applicable Canadian securities laws, the Securities Act or any state securities
laws in connection with the issuance of any such shares.  All of the outstanding
shares of capital stock of each of the Subsidiaries are owned beneficially and
of record by the respective Sentrex Company free and clear of all liens,
charges, encumbrances, options, rights of first refusal or limitations or
agreements regarding voting rights of any nature.  All of the
                                       3.
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<PAGE>
outstanding shares of capital stock of each Sentrex Company and each of the
Subsidiaries have been validly issued and are fully paid and nonassessable.

     2.4  TAXES.

     (a)  Each Sentrex Company has timely filed or been included in all Tax
Returns (as defined in SECTION 5.1 hereof) that are required to be filed by each
Sentrex Company with respect to the activities of such Sentrex Company and its
Subsidiaries, or in which such Sentrex Company is required to be included for
any period ending on or before the Closing Date, which Tax Returns are true,
correct and complete in all material respects, and such Sentrex Company has paid
all Taxes (as defined in SECTION 5.1 HEREOF) shown thereon to be due.

     (b)  Each Sentrex Company has paid or caused to be paid within the time and
in the manner prescribed by law all Taxes payable or owed by such Sentrex
Company and its Subsidiaries for all periods ending on or prior to the Closing
Date.

     (c)  Neither any Sentrex Company nor any Subsidiary has taken any action
that would require an adjustment pursuant to Section 481 of the Internal Revenue
Code of 1986, as amended (the "Code"), by reason of a change in accounting
method or otherwise.  Neither any Sentrex Company nor any Subsidiary has filed a
consent under Section 341(f)(1) of the Code or agreed to have the provisions of
Section 341(f)(2) of the Code apply to any disposition of "subsection (f)
assets" as such term is defined in Section 341(f)(4) of the Code.

     (d)  No Tax assessment or deficiency which has not been paid or for which
an adequate reserve has not been set aside, has been made or proposed against
any Sentrex Company or any Subsidiary, nor are any of the Tax Returns now being
or, to the best knowledge of the Shareholders, threatened to be examined or
audited, and no consents waiving or extending any applicable statutes of
limitations for the Tax Returns, or any Taxes required to be paid thereunder,
have been filed.  All Tax deficiencies determined as a result of any past
completed audit have been satisfied.  The Shareholders have delivered to Tetra
Tech complete and correct copies of all audit reports and statements of
deficiencies with respect to any tax assessed against or agreed to by any
Sentrex Company or any Subsidiary for the three most recent taxable periods for
which such audit reports and statements of deficiencies have been received by
such Sentrex Company or Subsidiary.

     (e)  Prior to the date hereof, each Sentrex Company has made available to
Tetra Tech complete, current and correct copies of the Tax Returns for the years
ended in 1995, 1996 and 1997.

     (f)  Without limiting the foregoing representations in any way, each
Sentrex Company and each Subsidiary has collected all sales, use and value added
Taxes required to be collected, and has remitted, or will remit on a timely
basis, such amounts to the appropriate
                                       4.
<PAGE>
<PAGE>
governmental authorities and have furnished properly completed exemption
certificates for all exempt transactions.

     (g)  Without limiting the foregoing representations in any way, each
Sentrex Company and each Subsidiary has properly withheld income and social
security or other similar Taxes and paid payroll Taxes with respect to all
persons properly characterized as employees for federal, state, provincial or
local Tax purposes.

     (h)  None of the assets of any Sentrex Company or any Subsidiary are
subject to any liens in respect of Taxes (other than for current Taxes not yet
due and payable).

     (i)  Neither any Sentrex Company nor any Subsidiary is a party to or bound
by any Tax sharing, Tax indemnity or Tax allocation agreement or other similar
arrangement.

     (j)  Neither any Sentrex Company nor any Subsidiary has made any payments,
is obligated to make any payments or is a party to any agreement that under
certain circumstances could obligate it to make any payments that will not be
deductible under Section 280G of the Code.

     (k)  The Shareholders have delivered to Tetra Tech complete and correct
copies of all provincial, state, local and foreign income or franchise Tax
Returns filed by each Sentrex Company and each Subsidiary for the three most
recent taxable years for which such Tax Returns have been filed immediately
preceding the Closing Date.  Other than with respect to taxes shown on Tax
Returns described in this subparagraph, neither any Sentrex Company nor any
Subsidiary is subject to any tax imposed on net income in any jurisdiction or by
any Taxing Authority.

     (l)  Neither any Sentrex Company nor any Subsidiary has executed or entered
into any closing agreement pursuant to Section 7121 of the Code, or any
predecessor provisions thereof or any similar provision of state or other law.

     2.5  TRANSACTIONS WITH AFFILIATES.  Except as set forth on SCHEDULE 2.5
attached hereto, neither the Shareholders, any of their Affiliates (as defined
below) or any members of their Families (as defined below), has any interest,
directly or indirectly, in any lease, lien, contract, license, encumbrance, loan
or other agreement to which any Sentrex Company or any Subsidiary is a party,
any interest (other than as a shareholder) in any properties or assets of any
Sentrex Company or any Subsidiary or any interest in any competitor, supplier or
customer of any Sentrex Company or any Subsidiary.  "Affiliate" shall mean, with
respect to any person, any other person controlling, controlled by or under
common control with the subject person, with control being evidenced by
ownership of more than 50% of the capital stock of a person or the ability to
direct the management or policies of another person through any other means.
"Family" shall mean any Shareholder's spouse, parents, children, siblings,
mothers and fathers-in-law, sons and daughters-in-law, and brothers and sisters-
in-law.
                                       5.
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<PAGE>
     2.6  FINANCIAL STATEMENTS.  True and complete copies of the financial
statements for each Sentrex Company and each Subsidiary, as listed on SCHEDULE
2.6 attached hereto (collectively the "Financial Statements"), have been
delivered to Tetra Tech prior to the date hereof, and no changes have been made
thereto since the date of delivery.  Except as expressly set forth or disclosed
in the notes, exhibits or schedules thereto or in SCHEDULE 2.6 hereto, the
Financial Statements (i) present fairly the financial position, results of
operations and cash flows of each Sentrex Company and Subsidiary as of and for
the periods then ended, (ii) were prepared or restated in accordance with United
States generally accepted accounting principles ("GAAP"), (iii) disclose all
liabilities, including contingent and/or unmatured liabilities as of the dates
thereof, which are required by GAAP to be disclosed thereon, and (iv) reflect
that such Sentrex Company and Subsidiary has fully and adequately reserved with
respect to receivables, for all reasonably anticipated uncollectible amounts,
losses and costs and expenses.

     2.7  TITLE TO PROPERTIES.  Each Sentrex Company and each Subsidiary has
good, valid and marketable title to all of the properties and assets which it
purports to own (personal and mixed, tangible and intangible), including,
without limitation, all the properties and assets listed on SCHEDULES 2.10 and
2.11 attached hereto.  Except as set forth on SCHEDULE 2.7, all such properties
and assets are free and clear of all title defects or objections, liens, claims,
charges, security interests or other encumbrances of any kind or nature
whatsoever.

     2.8  REAL PROPERTY.  Neither any Sentrex Company nor any Subsidiary owns
any real property.

     2.9  LEASES.  SCHEDULE 2.9 attached hereto contains a complete, current and
correct list of all leases pursuant to which each Sentrex Company and each
Subsidiary leases real or personal property, including all amendments thereto
(collectively, the "Leases").  Prior to the date hereof, there has been
delivered or made available to Tetra Tech complete, current and correct copies
of the Leases, and no changes have been made thereto since the date of delivery.
Each of the Leases is valid, binding and enforceable in accordance with its
terms, subject to judicial discretion regarding specific performance or other
equitable remedies, and except as may be limited by bankruptcy, reorganization,
insolvency, moratorium or other laws relating to or affecting the enforcement of
creditors' rights and remedies generally.  Except as set forth on SCHEDULE 2.9,
there are no existing material defaults by any Sentrex Company or any Subsidiary
under any of the Leases and no event has occurred which would constitute a
material default (or any event which, with the giving of notice or lapse of time
or both, would constitute a material default) thereunder by such Sentrex Company
or Subsidiary.

     2.10 FIXED ASSETS.  SCHEDULE 2.10 attached hereto contains a complete,
current and correct list, in all material respects, of all fixtures, furniture
and equipment owned, leased or used by each Sentrex Company and each Subsidiary
("Fixed Assets").  The Fixed Assets are in good operating condition and repair,
normal wear and tear excepted, and are adequate for the uses to which they are
being put.  None of the Fixed Assets are in need of maintenance or repairs,
except for ordinary, routine maintenance and repairs.
                                       6.
<PAGE>
<PAGE>
     2.11 INTANGIBLE PERSONAL PROPERTY.  SCHEDULE 2.11 attached hereto contains
a complete, current and correct list of each domestic and foreign patent, patent
application, invention disclosure, copyright, trademark, trademark registration,
trade name, service mark and applications for any of the foregoing, and any
software codes, trade secrets and proprietary know-how owned by each Sentrex
Company and each Subsidiary or used in the conduct of their respective
businesses ("Intangible Personal Property").  Except as set forth in SCHEDULE
2.11, (a) such Sentrex Company or Subsidiary has the right and authority to use
all Intangible Personal Property required for the conduct of its businesses in
the manner presently conducted, and (b)  to the best knowledge of the
Shareholders, such use does not conflict with, infringe upon or violate any
trademark, trade name, copyright, patent or patent rights of any other person or
entity.  There have not been any actions or other judicial or adversary
proceedings involving any Sentrex Company or any Subsidiary concerning the
validity of the Intangible Personal Property, nor, to the best knowledge of the
Shareholders, is any such action or proceeding threatened.

     2.12 ACCOUNTS RECEIVABLE.  A complete, current and correct list of all
accounts receivable of each Sentrex Company and each Subsidiary as of the
Closing Date ("Accounts Receivable") has been delivered to Tetra Tech prior to
the date hereof, and sets forth the aging of such Accounts Receivable.  The
Accounts Receivable represent BONA FIDE sales actually made or services actually
performed on or prior to such date in the ordinary course of business consistent
with past practices.  Except as set forth on SCHEDULE 2.12 attached hereto,
there is no contest, claim or right of set-off contained in any oral or written
agreement with any account debtor relating to the amount or validity of any
Account Receivable, or any other account receivable created after the Closing
Date.  The Accounts Receivable (net of any reserves reflected in the Financial
Statements) are valid and collectible in the ordinary course of business.  The
reserves reflected in the Financial Statements have been established in the
ordinary course of business, in accordance with GAAP, and are consistent with
past practices.

     2.13 LICENSES AND PERMITS.  SCHEDULE 2.13 attached hereto contains a
complete, current and correct list of all governmental licenses, permits,
franchises, rights and privileges necessary for the present conduct of each
Sentrex Company's and each Subsidiary's business (the "Licenses").  Except as
set forth in SCHEDULE 2.13, the Sentrex Companies and the Subsidiaries possess
all such Licenses.  Each of the Licenses is in full force and effect, and there
are no pending or, to the best knowledge of the Shareholders, threatened claims
or proceedings challenging the validity of or seeking to revoke or discontinue,
any of the Licenses.  Prior to the date hereof, there has been delivered or made
available to Tetra Tech a complete, current and correct copy of each of the
Licenses.

     2.14 INSURANCE.  SCHEDULE 2.14 attached hereto contains a complete, current
and correct description of all existing policies of fire, liability, workers'
compensation and all other forms of insurance maintained by each Sentrex Company
and each Subsidiary.  Except as set forth on SCHEDULE 2.14, all such policies
are in full force and effect, all premiums with respect thereto covering all
periods up to and including the Closing Date have been paid, and no notice of
cancellation, termination or denial of coverage has been received with respect
to
                                       7.
<PAGE>
<PAGE>
any such policy.  Such policies (a) are adequate for compliance with all
agreements or instruments to which the Sentrex Companies and the Subsidiaries
are parties, or pursuant to which any of their businesses, properties or assets
may be subject, (b) are valid, outstanding and enforceable, (c) provide
insurance coverage in the amounts indicated in such policies for the Sentrex
Companies' and the Subsidiaries' businesses, properties, assets and operations
of the Sentrex Companies and the Subsidiaries as presently conducted and (d)
will remain in full force and effect through the respective dates set forth on
SCHEDULE 2.14, without the payment of additional premiums.  SCHEDULE 2.14 also
describes all claims of the Sentrex Companies and the Subsidiaries which are
pending under such insurance policies or have been paid to the Sentrex Companies
and the Subsidiaries since January 1, 1995.  Since January 1, 1995, neither any
Sentrex Company nor any Subsidiary has been refused coverage by any insurance
carrier with respect to its properties, assets or operations, nor has its
coverage been limited, by any insurance carrier to which it has applied for any
such insurance or with which it has carried insurance.  Prior to the date
hereof, there have been delivered or made available to Tetra Tech complete,
current and correct copies of all of the policies of insurance which are
maintained by the Sentrex Companies and the Subsidiaries.

     2.15 ABSENCE OF CERTAIN CHANGES.  Except as set forth in SCHEDULE 2.15
attached hereto, and except for the transactions specifically contemplated under
this Agreement, since August 31, 1998, there has not been:

          (a)  Any declaration or payment of dividends by any Sentrex Company
or, except in the ordinary course of business, any transfer of properties or
assets of any kind whatsoever by any Sentrex Company to its shareholders;

          (b)  Any transaction of any Sentrex Company or any Subsidiary not in
the ordinary course of business;

          (c)  Any material adverse change in the results of the operations,
financial condition or business of any Sentrex Company or any Subsidiary;

          (d)  Any loan or advance by any Sentrex Company or any Subsidiary to
any person, except a normal travel advance or other reasonable expense advance
to an officer or employee of any Sentrex Company or any Subsidiary and normal
trade terms extended to customers;

          (e)  Any damage, destruction or loss, whether or not covered by
insurance, which has had or is reasonably likely to have a material adverse
effect on any of the properties, assets or business of any Sentrex Company or
any Subsidiary;

          (f)  Any sale or transfer of any properties or assets not in the
ordinary course of business or any cancellation of any debts or claims of any
Sentrex Company or any Subsidiary;
                                       8.
<PAGE>
<PAGE>
          (g)  Any mortgage, pledge or subjection to lien, charge or encumbrance
of any kind on any of any Sentrex Company's or any Subsidiary's properties or
assets, or any assumption of, or taking any properties or assets subject to, any
liability;

          (h)  Any amendment, modification or termination of any material
contract or agreement to which any Sentrex Company or any Subsidiary is a party
or pursuant to which its properties or assets may be bound;

          (i)  Any sale or granting to any party or parties of any license,
franchise, option or other right of any nature whatsoever with respect to any
Sentrex Company's or any Subsidiary's business or termination of any such
rights;

          (j)  Any increase in, or commitment to increase, the direct or
indirect compensation payable or to become payable to any officer or director of
any Sentrex Company or any Subsidiary, its employees, or to any of its
Affiliates, or any commitment to make severance, bonus or special payments to
any of such parties, upon a change in ownership or management of any Sentrex
Company or any Subsidiary or upon termination of such parties;

          (k)  Any adoption by any Sentrex Company or any Subsidiary of any new
Benefit Plan (as that term is defined in SECTION 2.22), or amendment to any
Benefit Plan to provide any new or additional plans, programs, contracts or
arrangements involving direct or indirect compensation to any officer, director,
employee, former employee, or their dependents or beneficiaries, of any Sentrex
Company or any Subsidiary;

          (l)  Any alteration in the manner of keeping the books, accounts or
records of any Sentrex Company or any Subsidiary or in the manner of preparing
the Financial Statements, or in the accounting practices of any Sentrex Company
or any Subsidiary, except as may be required by any modification or change in
GAAP;

          (m)  Any proposals greater than $50,000 for fixed price contracts or
cost-type contracts containing rate caps or not to exceed prices; or

          (n)  The occurrence of any other event or the development of any other
condition which has had or is reasonably likely to have a material adverse
effect on the results of operations, financial condition or business of any
Sentrex Company or any Subsidiary.

     2.16 COMPLIANCE WITH CONTRACTS.  SCHEULE 2.16 attached hereto contains a
complete, current and correct list of all material contracts, commitments,
obligations or agreements of each Sentrex Company and each Subsidiary.  Other
than as set forth on SCHEDULE 2.16, no event has occurred which would constitute
a default (or any event which, with the giving of notice or lapse of time or
both, would constitute a default) under any term or provision of any of the
Contracts and thereby allow another party to terminate and/or claim damages
therefor.  Each of the Contracts is in full force and effect and is the legal,
valid and binding obligation of the respective Sentrex Company or Subsidiary
and, to the best knowledge of the Shareholders,
                                       9.
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<PAGE>
of the other parties thereto, enforceable in accordance with its terms, subject
to judicial discretion regarding specific performance or other equitable
remedies, and except as may be limited by bankruptcy, reorganization,
insolvency, moratorium or other laws relating to or affecting the enforcement of
creditors' rights and remedies generally.  Neither any Sentrex Company nor any
Subsidiary is a party to any Contract that restricts it from carrying on its
business or any part thereof, or from competing in any line of business with any
person, corporation or entity.  Prior to the date hereof, there has been
delivered or made available to Tetra Tech a complete, current and correct copy
of each of the written Contracts, as well as a written summary of each of the
oral Contracts, including all amendments and modifications thereto.

     2.17 COMPLIANCE WITH LAWS.  Except as disclosed on SCHEDULE 2.17, each
Sentrex Company's and each Subsidiary's business has been conducted in
compliance with all, and is not in violation of, applicable laws, statutes,
ordinances, rules, regulations, orders and other requirements of all Canadian
and United States governmental authorities, and of all territories, states,
provinces, municipalities and other political subdivisions and agencies thereof,
having jurisdiction over the Sentrex Companies and the Subsidiaries and their
businesses, including without limitation all such laws, regulations, ordinances
and requirements relating to insurance, environmental, antitrust, consumer
protection, labor and employment, zoning and land use, immigration, health,
occupational safety, pension and securities matters, except where noncompliance
or violation would not have a material adverse effect on the financial
condition, results of operation or business of such Sentrex Company or
Subsidiary.  Except as disclosed on SCHEDULE 2.17, since January 1, 1997,
neither any Sentrex Company nor any Subsidiary has received any written
notification of any asserted present or past failure by such Sentrex Company or
such Subsidiary to comply with such laws, statutes, ordinances, rules,
regulations, orders or other requirements that is unresolved as of the date
hereof.

     2.18 NO UNDISCLOSED LIABILITIES.  Except as disclosed in the Financial
Statements or on SCHEDULE 2.18 attached hereto, neither any Sentrex Company nor
any Subsidiary is directly or indirectly (i) liable, by guaranty, surety or
otherwise, upon or with respect to, or (ii) obligated in any way to provide
funds in respect of, or (iii) obligated to guaranty or assume any debt, dividend
or other obligation of any person, corporation, association, partnership,
limited liability company or other entity.  Specifically, but in no way limiting
the foregoing, neither any Sentrex Company nor any Subsidiary has any contingent
liability arising in connection with or in any way related to the divestiture of
the SEI's Ottawa, Ontario office.

     2.19 EMPLOYEES.  SCHEDULE 2.19 attached hereto contains a complete, current
and correct list of all of each Sentrex Company's and each Subsidiary's
employees ("Employees"), which includes the compensation payable to each of the
Employees.  Except to the extent set forth in SCHEDULE 2.19:

          (a)  Each Sentrex Company and each Subsidiary is in material
compliance with all U.S. and Canadian federal, state, provincial and local laws,
statutes, ordinances,
                                      10.
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<PAGE>
rules, regulations, orders, guidelines and other requirements relating to the
employment of labor, including without limitation Title VII of the federal Civil
Rights Act of 1964, the federal Age Discrimination in Employment Act of 1967,
the federal Americans with Disabilities Act, the federal Employee Retirement
Income Security Act of 1974 ("ERISA"), and any and all provisions thereof
relating to wages, hours, collective bargaining and the payment of social
security and similar Taxes;

          (b)  There is no pending or, to the best knowledge of the
Shareholders, threatened charge, complaint, allegation, application or other
process or claim against any Sentrex Company or any Subsidiary before any
federal, territorial, state, provincial or local or other governmental or
administrative agency or other entity;

          (c)  No employees of any Sentrex Company or any Subsidiary are covered
by any collective bargaining agreement, nor, to the best knowledge of the
Shareholders, is there any effort being made by any union to organize any
Sentrex Company's or any Subsidiary's employees; and

          (d)  Each Sentrex Company and each Subsidiary has paid and performed
all obligations when due with respect to its employees, consultants, agents,
officers and directors, including without limitation the payment of any accrued
and payable wages, severance pay, vacation pay, benefits and commissions, except
those obligations which are in good faith being challenged by such Sentrex
Company or such Subsidiary as not valid obligations as more fully described on
SCHEDULE 2.19.

     2.20 LITIGATION.  Except as set forth in SCHEDULE 2.20 attached hereto:

          (a)  There is no pending or, to the best knowledge of the
Shareholders, threatened action, suit, arbitration proceeding, investigation or
inquiry before any court or governmental or administrative body or agency, or
any private arbitration tribunal, against, relating to or affecting any Sentrex
Company or any Subsidiary or any director, officer or employee of any Sentrex
Company or any Subsidiary in his or her capacity as such, or the assets,
properties or business of any Sentrex Company or any Subsidiary, or the
transactions contemplated by this Agreement, nor to the best knowledge of the
Shareholders, are there any facts or circumstances which could reasonably lead
to or provide the basis for any such threatened action, suit, arbitration
proceeding, investigation or inquiry;

          (b)  There is not in effect any order, judgment or decree of any court
or governmental or administrative body or agency enjoining, barring, suspending,
prohibiting or otherwise limiting any Sentrex Company or any Subsidiary, or any
officer, director or employee of any Sentrex Company or any Subsidiary, from
conducting or engaging in any aspect of any Sentrex Company's or any
Subsidiary's business, or requiring any Sentrex Company or any Subsidiary, or
any officer, director or employee of any Sentrex Company or any Subsidiary to
take certain action with respect to any aspect of any Sentrex Company's or any
Subsidiary's business which could reasonably be anticipated to have a material
adverse
                                      11.
<PAGE>
<PAGE>
effect on the business, operations or financial condition of such Sentrex
Company or Subsidiary; and

          (c)  Neither any Sentrex Company nor any Subsidiary has received
written notice that it is in violation of or in default under any order,
judgment, writ, injunction or decree of any court or governmental or
administrative body or agency.

     2.21 ENVIRONMENTAL COMPLIANCE.

          (a)  The Shareholders have no knowledge of any past or present events,
settlements, consent decrees, conditions, circumstances, activities, practices,
incidents, actions or plans, or federal, state, local or private litigation or
proceedings relating to Hazardous Substances, which may materially adversely
impact any Sentrex Company's or Subsidiary's financial condition, or interfere
with or prevent any Sentrex Company's or any Subsidiary's continued compliance
with, Hazardous Materials Laws (as defined below), including those relating to
the manufacture, storage or disposal of Hazardous Substances (as defined below).

          (b)  Neither the Shareholders nor any Sentrex Company or any
Subsidiary has discovered or caused, and, to the best knowledge of the
Shareholders, no other person has discovered or caused, any discharge, emission,
disposal or release of Hazardous Substances on any Sentrex Company's or any
Subsidiary's premises, or any occurrence or condition on such premises or in the
vicinity of such premises, which could make such premises subject to
restrictions on the ownership, occupancy, transferability or use under any
Hazardous Materials Laws.

          (c)  No lien in favor of any governmental authority for liability
under or resulting from Hazardous Materials Laws, or damages arising from, or
costs incurred by such governmental authority in response to, a release of
Hazardous Substances is now, or, to the best knowledge of the Shareholders, has
ever been filed against any Sentrex Company's or any Subsidiary's premises.

          (d)  Neither any Sentrex Company nor any Subsidiary is responsible or
potentially responsible (as defined under Hazardous Materials Laws), for the
remediation or cost of remediation of wastes, substances or materials at, on or
below any property to which  such Company or Subsidiary has possession as a
result of the manufacture, storage or disposal of Hazardous Substances by such
Sentrex Company or Subsidiary, or at, on or below any land adjacent thereto or
in connection with any site or location, wherever located, where pollutants,
contaminants or hazardous or toxic wastes, substances or materials shall have
been deposited, stored, treated, reclaimed, disposed, placed or otherwise come
to be located due to acts or omissions of such Sentrex Company or Subsidiary.

          (e)  Each Sentrex Company and each Subsidiary has made available to
Tetra Tech copies of all (i) environmental audits, studies and reports assessing
Hazardous Substance risks at any property previously or currently owned, leased
or operated by any Sentrex
                                      12.
<PAGE>
<PAGE>
Company or Subsidiary, and (ii) communications, agreements and pleadings with
any governmental authority or any private entity or individual relating in any
way to the presence, discharge, release or threat of release of Hazardous
Substances at, on under or about any property previously or currently owned,
leased or operated by any Sentrex Company or Subsidiary.

          (f)  "Hazardous Materials Law" shall mean any Canadian or United
States federal, state, provincial or local law, order, rule, guideline or
regulation relating to the discharge, remediation, removal, manufacture,
processing, distribution, use, treatment, storage, disposal, transport or
handling of Hazardous Substances.

          (g)  "Hazardous Substance" shall mean any substance, material,
chemical or waste, the presence, quantity or concentration of which requires
investigation or remediation under, or may form the basis for liability under
Hazardous Materials Laws, or which is regulated by, any Canadian or United
States federal, provincial, state or local governmental authority, due to its
properties of being toxic, hazardous, explosive, corrosive, flammable,
infectious, radioactive, carcinogenic or mutagenic.

     2.22 EMPLOYEE BENEFITS.

          (a)  SCHEDULE 2.22 sets forth a true and complete list of:

               (i)  All employee benefit plans, including those as defined in
     Section 3(3) of ERISA; and

               (ii) All other profit-sharing, deferred compensation, bonus,
     stock option, stock purchase, stock bonus, phantom stock, vacation pay,
     holiday pay, severance, dependent care assistance, excess benefit,
     incentive compensation, salary continuation, medical, life or other
     insurance, supplemental unemployment and other employee benefit plans,
     programs, agreements or arrangements, including all unwritten employee
     benefit plans, programs, agreements and arrangements, if any;

maintained or contributed to by any Sentrex Company or any Subsidiary for the
benefit of its employees (or former employees) and/or their beneficiaries.  Both
of these types of plans shall be collectively referred to as "Benefit Plans."
An arrangement will not fail to be a Benefit Plan simply because it only covers
one individual, or because any Sentrex Company's or any Subsidiary's obligations
under the plan arise by reason of its being a "successor employer" under
applicable law.

          (b)  There has been delivered or made available to Tetra Tech a true
and complete copy of each Benefit Plan and any related funding agreements (e.g.,
trust agreements or insurance contracts), including all amendments (and SCHEDULE
2.22 includes a description of any such amendment that is not in writing).
                                      13.
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<PAGE>
          (c)  Neither any Sentrex Company, any Subsidiary nor any other trade
or business, whether or not incorporated, that together with any Sentrex Company
or any Subsidiary would be deemed a "single employer" within the meaning of
Section 4001 of ERISA either maintains or at any time has maintained any (i)
employee benefit plan, as that term is defined at Section 3(3) of ERISA, (ii)
any employee retirement plan subject to the requirements of Section 401(a) et.
seq. of the Code (or any predecessor thereto) or (iii) any employee welfare plan
subject to the requirements of the Consolidated Omnibus Budget Reconciliation
Act of 1985 ("COBRA").

          (d)  All costs of administering and contributions required to be made
by any Sentrex Company or any Subsidiary to each Benefit Plan under the terms of
that Benefit Plan, ERISA, the Code or any other applicable law have been timely
made, and are fully deductible.  All amounts properly accrued to date as
liabilities of any Sentrex Company or Subsidiary under or with respect to each
Benefit Plan (including administrative expenses and incurred but not reported
claims) for the current plan year of the Benefit Plan have been recorded on such
Sentrex Company's or Subsidiary's books.

          (e)  Except as set forth on SCHEDULE 2.22, each Benefit Plan complies
currently, and has complied in the past, both in form and operation, with all
applicable laws, including but not limited to ERISA and the Code.  Each Benefit
Plan has been operated in accordance with its terms.

          (f)  Except as set forth on SCHEDULE 2.22, neither any Sentrex Company
nor any Subsidiary maintains any plan that provides (or will provide) medical or
death benefits to one or more, current or future former employees (including
retirees) beyond their retirement or other termination of service, other than
benefits that are required to be provided pursuant to Section 4980B of the Code
or state law continuation coverage or conversion rights.

          (g)  Except as set forth on SCHEDULE 2.22, there are no proceedings or
lawsuits, and to the best knowledge of the Shareholders, there are no
investigations, either currently in progress or expected to be instituted in the
future, relating to any Benefit Plan, by any administrative agency, whether
local, state, provincial or federal.

          (h)  Except as set forth on SCHEDULE 2.22, there are no pending or
threatened lawsuits or other claims (other than routine claims for benefits
under the plan) against or involving any Benefit Plan.

          (i)  Neither any Sentrex Company nor any Subsidiary has any intention
or commitment, whether legally binding or not, to create any additional Benefit
Plan, or to modify or change any existing Benefit Plan.  The benefits under all
Benefit Plans are as represented, and except in the ordinary course of business
and consistent with past practices or as required by law, have not been, and
will not be, increased subsequent to the date documents are provided to Tetra
Tech.
                                      14.
<PAGE>
<PAGE>
          (j)  Except as set forth on SCHEDULE 2.22, none of the Benefit Plans
or any other employment agreement or arrangement entered into by any Sentrex
Company or any Subsidiary will entitle any current or former employee to any
benefits or other compensation that become payable solely as a result of the
consummation of the transactions contemplated by this Agreement.

          (k)  Except as set forth on SCHEDULE 2.22, all reports, notices and
other disclosure relating to Benefit Plans required to be filed with, or
furnished to, governmental entities, plan participants or plan beneficiaries
have been timely filed and furnished in accordance with applicable law.

          (l)  To the knowledge of the Shareholders, none of the persons
performing services for any Sentrex Company or any Subsidiary have been
improperly classified as independent contractors or as being exempt from the
payment of wages for overtime.

          (m)  SCHEDULE 2.22 lists each individual who is absent from active
employment with any Sentrex Company or any Subsidiary by reason of (i) short-
term or long term disability, (ii) leave of absence under the Family and Medical
Leave Act of 1993 (or comparable state or provincial statute), (iii) military
leave (under conditions that give the employee re-employment rights) or
(iv) other Sentrex Company-approved or Subsidiary-approved leave of absence.

     2.23 BANK ACCOUNTS.  SCHEDULE 2.23 sets forth the names and locations of
all banks, trust companies, savings and loan associations and other financial
institutions at which any Sentrex Company or any Subsidiary maintains safe
deposit boxes or accounts of any nature.

     2.24 INVENTORY.  With respect to inventory held by any Sentrex Company or
Subsidiary that is supplied by a customer of a Sentrex Company or Subsidiary,
there are no pending or, to the knowledge of the Shareholders, threatened claims
by any such customer with respect to lost, damaged or destroyed inventory.

     2.25 CORPORATE RECORDS.  The minute books of each Sentrex Company and each
Subsidiary reflect all material actions taken to this date by the shareholders,
board of directors and committees of the board of directors of such Sentrex
Company or Subsidiary, and contain true and complete copies of their respective
charters or articles, Bylaws and all amendments thereto.

     2.26 ACCOUNTING RECORDS.  Each Sentrex Company and each Subsidiary
maintains accounting records which fairly and validly reflect, in all material
respects, its transactions and maintain accounting controls sufficient to
provide reasonable assurances that such transactions are, in all material
respects, (i) executed in accordance with management's general or specific
authorization, and (ii) recorded as necessary to permit the preparation of
financial statements in conformity with GAAP.
                                      15.
<PAGE>
<PAGE>
     2.27 BROKERS AND FINDERS.  Neither any Sentrex Company, any Subsidiary nor
any of the Shareholders have engaged or authorized any broker, finder,
investment banker or other third party to act on their behalf, directly or
indirectly, as a broker, finder, investment banker or in any other like capacity
in connection with this Agreement or the transactions contemplated hereby, or
has consented to or acquiesced in anyone so acting, and the Shareholders do not
know of any claim for compensation from any such broker, finder, investment
banker or other third party for so acting on behalf of the Shareholders or of
any basis for such a claim.

     2.28 ACCURACY OF REPRESENTATIONS AND WARRANTIES.  No representation or
warranty made in this Agreement or any other document delivered in connection
herewith, by or on behalf of any Sentrex Company, any Subsidiary or the
Shareholders to Tetra Tech, with respect to any Sentrex Company, any Subsidiary
or the Shareholders, contains any untrue statement of a material fact or omits
to state a material fact necessary in order to make the statements so made, in
light of the circumstances under which they are made, not misleading.


                                   ARTICLE 3

               REPRESENTATIONS AND WARRANTIES OF EACH SHAREHOLDER

     Each Shareholder, severally and not jointly, represents and warrants to
Tetra Tech as follows:

     3.1  TITLE TO SHARES.  The Shareholder is the record and beneficial owner
of the Shares set forth opposite such Shareholder's name on SCHEDULE 2.3 hereto,
free and clear of any liens, encumbrances, security interests, restrictions or
claims whatsoever, with full power and authority to convey such shares in
accordance with the terms of this Agreement.

     3.2  AUTHORIZATION AND APPROVALS.  The Shareholder has all requisite legal
power and authority to enter into this Agreement, the Employment and
Noncompetition Agreement (as hereinafter defined), and the Registration Rights
Agreement (as hereinafter defined), and to perform his obligations hereunder and
thereunder.  This Agreement, the Employment and Noncompetition Agreement, and
the Registration Rights Agreement have been duly executed and delivered by the
Shareholder and, upon execution and delivery, will constitute the legal, valid
and binding obligations of the Shareholder, enforceable in accordance with their
terms, subject to judicial discretion regarding specific performance or other
equitable remedies, and except as may be limited by bankruptcy, reorganization,
insolvency, moratorium or other laws relating to or affecting the enforcement of
creditors' rights and remedies generally.  No approvals or consents by, or
filings with, any Canadian or United States federal, state, provincial,
municipal, foreign or other court or governmental or administrative body, agency
or other third party is required in connection with the execution and delivery
by the Shareholder of this Agreement, the Employment and Noncompetition
Agreement, and the Registration Rights Agreement or the consummation by the
Shareholder of the transactions
                                      16.
<PAGE>
<PAGE>
contemplated hereby and thereby, except for those filings required by the
Registration Rights Agreement and those which, if not obtained, would not have a
material adverse impact on the ability of the Shareholder to execute and deliver
this Agreement, the Employment and Noncompetition Agreement, and the
Registration Rights Agreement, or to consummate the transactions contemplated
hereby and thereby.

     3.3  NO VIOLATIONS.  Neither the execution and delivery of this Agreement,
the Employment and Noncompetition Agreement, and the Registration Rights
Agreement, nor the consummation of the transactions contemplated hereby and
thereby will (a) violate, or be in conflict with, or constitute a default (or
other event which, with the giving of notice or lapse of time or both, would
constitute a default) under, or give rise to any right of termination,
cancellation or acceleration under any of the terms, conditions or provisions of
any material lease, license, promissory note, contract, agreement, mortgage,
deed of trust or other instrument or document to which the Shareholder is a
party or by which the Shareholder or any of his or its properties or assets may
be bound, other than obligations to be discharged on or immediately after
Closing, (b) violate any order, writ, injunction, decree, law, statute, rule or
regulation of any court or governmental authority applicable to the Shareholder
or any of his or its properties or assets or (c) give rise to a declaration or
imposition of any claim, lien, charge, security interest or encumbrance of any
nature whatsoever upon the Shares held by the Shareholder or upon any of the
assets of any Sentrex Company or any Subsidiary.

     3.4  SECURITIES LAW MATTERS.  The Shareholder hereby confirms that the
Shareholder has been informed that the shares of Tetra Tech Common Stock
issuable upon exchange for TTC Exchangeable Shares pursuant to this Agreement
will be restricted securities under the Securities Act and may not be resold or
transferred unless first registered under the federal securities laws or unless
an exemption from such registration is available.  Accordingly, the Shareholder
hereby acknowledges that, except for sales of shares of Tetra Tech Common Stock
pursuant to the Registration Statement filed in accordance with the Registration
Rights Agreement, the Shareholder is prepared to hold Tetra Tech Common Stock
during the applicable restricted period and that the Shareholder is aware that,
due to a one year holding period requirement set forth in Rule 144(d), Rule 144
of the Securities and Exchange Commission ("SEC") issued under the Securities
Act is not presently available to exempt the offer and sale of Tetra Tech Common
Stock from the registration requirements of the Securities Act.  The Shareholder
is aware of the adoption of Rule 144 promulgated under the Securities Act by the
SEC, which permits limited public resales of securities acquired in a nonpublic
offering, subject to the satisfaction of certain conditions.  The Shareholder
understands that Rule 144 is conditioned upon, among other things:  (i) the
availability of certain current public information about Tetra Tech, (ii) the
resale occurring not fewer than one (1) year after the party has purchased and
paid for the securities to be sold, (iii) the sale being made through a broker
in an unsolicited "broker's transaction", and (iv) the amount of securities
being sold during any three-month period not exceeding specified limitations.
Prior to the Shareholder's acquisition of the shares of Tetra Tech Common Stock,
the Shareholder will acquire sufficient information about the Tetra Tech to
reach an informed and knowledgeable decision to acquire Tetra Tech Common Stock.
The Shareholder has such
                                      17.
<PAGE>
<PAGE>
knowledge and experience in financial and business matters so as to make the
Shareholder capable of utilizing such information to evaluate the risks of the
prospective investment and to make an informed investment decision.  The
Shareholder will acquire Tetra Tech Common Stock for investment purposes without
a view to or for sale in connection with such shares, and is able to bear the
economic risk of the investment in Tetra Tech Common Stock.

     3.5  RESIDENCY.  The Shareholder is not a non-resident of Canada for
purposes of Section 116 of the INCOME TAX ACT (Canada).


                                   ARTICLE 4

                         REPRESENTATIONS AND WARRANTIES
                             OF TETRA TECH AND TTC

     Tetra Tech and TTC jointly and severally represent and warrant to the
Shareholders as follows:

     4.1  ORGANIZATION AND POWER; FOREIGN QUALIFICATION.  Each of Tetra Tech and
TTC is a corporation duly organized, validly existing and in good standing under
the laws of the jurisdiction of its incorporation, and has all requisite
corporate power and authority to own, lease and operate its properties, and to
carry on its businesses, as such are now being conducted.  Tetra Tech is duly
qualified to transact business and is in good standing in every jurisdiction in
which the character of its business makes such qualification necessary, except
for such jurisdictions where the failure to so qualify would not have a material
adverse effect on the financial condition, results of operation or business of
Tetra Tech.  TTC has not transacted business prior to the date hereof.

     4.2  CAPITAL STRUCTURE.  The authorized capital stock of Tetra Tech
consists of 2,000,000 shares of Preferred Stock, $.01 par value, of which no
shares are issued and outstanding, and 50,000,000 shares of common stock, $.01
par value, of which 28,613,393 shares were issued and outstanding as of
September 16, 1998.  Except for (i) the transactions contemplated pursuant to
this Agreement, (ii) 2,372,296 outstanding stock options as of September 16,
1998 granted to Tetra Tech's officers, directors, employees and advisors and
(iii) 2,455,888 stock options or shares of Tetra Tech Common Stock that may be
granted or issued pursuant to existing plans as of September 16, 1998, there are
no outstanding options, warrants, convertible debt or securities, calls,
agreements, arrangements, commitments, understandings or other rights to
purchase any of Tetra Tech's capital stock, or securities convertible into or
exchangeable for any such capital stock.  All of the outstanding shares of
capital stock of Tetra Tech have been validly issued and are fully paid and
nonassessable.  [Insert capitalization of TTC]

     4.3  AUTHORIZATION AND APPROVALS.  Each of Tetra Tech and TTC, as
applicable, has all requisite corporate power and authority to enter into this
Agreement, the Employment and
                                      18.
<PAGE>
<PAGE>
Noncompetition Agreements, and the Registration Rights Agreement and to perform
its obligations hereunder and thereunder.  This Agreement, Employment and
Noncompetition Agreements, and the Registration Rights Agreement have been duly
executed and delivered by Tetra Tech and TTC, as applicable, and constitute the
legal, valid and binding obligations of Tetra Tech and TTC, as applicable,
enforceable in accordance with their terms, subject to judicial discretion
regarding specific performance or other equitable remedies, and except as may be
limited by bankruptcy, reorganization, insolvency, moratorium or other laws
relating to or affecting the enforcement of creditors' rights and remedies
generally.  This Agreement, the Employment and Noncompetition Agreements, and
the Registration Rights Agreement have been, duly and validly authorized by and
approved by all requisite action on the part of Tetra Tech and TTC, as
applicable.  No further approvals or consents by, or filings with, any federal,
state, provincial, municipal, foreign or other court or governmental or
administrative body, agency or other third party is required in connection with
the execution and delivery by Tetra Tech and TTC, as applicable, of this
Agreement, the Employment and Noncompetition Agreements, and the Registration
Rights Agreement, or the consummation by Tetra Tech and TTC, as applicable, of
the transactions contemplated hereby and thereby, except for those filings
required by the Registration Rights Agreement  and those which, if not obtained,
would not have a material adverse impact on the ability of Tetra Tech to perform
its businesses as currently conducted or the ability of Tetra Tech and TTC, as
applicable, to execute and deliver this Agreement, the Employment and
Noncompetition Agreements, and the Registration Rights Agreement, or to
consummate the transactions contemplated hereby and thereby.

     4.4  NO CONFLICTS.  Neither the execution and delivery of this Agreement,
the Employment and Noncompetition Agreements, and the Registration Rights
Agreement, nor the consummation of the transactions contemplated hereby or
thereby will (a) violate any provisions of the charter, articles or Bylaws of
Tetra Tech or TTC, (b) violate, or be in conflict with, or constitute a default
(or other event which, with the giving of notice or lapse of time or both, would
constitute a default) under, or give rise to any right of termination,
cancellation or acceleration under any of the terms, conditions or provisions of
any material lease, license, promissory note, contract, agreement, mortgage,
deed of trust or other instrument or document to which Tetra Tech or TTC is a
party or by which Tetra Tech or TTC or any of their respective properties or
assets may be bound, (c) violate any order, writ, injunction, decree, law,
statute, rule or regulation of any court or governmental authority applicable to
Tetra Tech or TTC or any of their respective properties or assets or (d) give
rise to a declaration or imposition of any claim, lien, charge, security
interest or encumbrance of any nature whatsoever upon any of the assets of
either Tetra Tech or TTC.

     4.5  FINANIAL STATEMENTS AND SEC REPORTS.  Tetra Tech has timely filed all
required forms, reports, statements and documents with the SEC, all of which
have complied in all material respects with all applicable requirements of the
Securities Act or the Securities Exchange Act of 1934, as amended.  Tetra Tech
has heretofore delivered or made available to the Shareholders true and complete
copies of (i) its Annual Report on Form 10-K for the fiscal year ended September
29, 1997, (ii) its Quarterly Reports on Form 10-Q for the fiscal quarters ended
December 28, 1997, March 29, 1998 and June 29, 1998, (iii) its proxy statement
                                      19.
<PAGE>
<PAGE>
relating to its Annual Meeting of Stockholders held on February 11, 1998 and
Special Meeting of Stockholders to be held on September 14, 1998, and (iv) all
other reports, statements and registration statements filed or required to be
filed by it with the SEC (the documents referred to in CLAUSES (i), (ii), (iii)
and (iv) being hereinafter referred to as the "Tetra Tech SEC Reports").  As of
their respective dates, the Tetra Tech SEC Reports did not contain any untrue
statement of a material fact or omit to state a material fact necessary in order
to make the statements made therein, in light of the circumstances under which
they were made, not misleading.  The financial statements (including any related
notes) of Tetra Tech included in the Tetra Tech SEC Reports were prepared in
conformity with GAAP applied on a consistent basis, and present fairly the
consolidated financial position, results of operations and cash flows of the
Tetra Tech and its consolidated subsidiaries as of the date and for the periods
indicated, subject, in the case of unaudited interim consolidated financial
statements, to condensation, the absence of certain notes thereto and normal
year-end audit adjustments.

     4.6  BROKERS AND FINDERS.  Neither Tetra Tech nor TTC has engaged or
authorized any broker, finder, investment banker or other third party to act on
its behalf, directly or indirectly, as a broker, finder, investment banker or in
any other like capacity in connection with this Agreement or the transactions
contemplated hereby, or consented to or acquiesced in anyone so acting, and
neither Tetra Tech nor TTC knows of any claim for compensation from any such
broker, finder, investment banker or other third party for so acting on behalf
of Tetra Tech or TTC or of any basis for such a claim.

     4.7  NO MATERIAL ADVERSE CHANGES.  Since June 29, 1998, there has not
occurred any event, nor has there been the development of any condition, which
has had or is reasonably likely to have a material adverse effect on the results
of operations, financial condition or business of Tetra Tech and its
subsidiaries.

     4.8  ACCURACY OF REPRESENTATIONS AND WARRANTIES.  No representation or
warranty made in this Agreement or any other document delivered in connection
herewith, by or on behalf of Tetra Tech or TTC to the Shareholders, with respect
to Tetra Tech or TTC contains any untrue statement of a material fact or omits
to state a material fact necessary in order to make the statements so made, in
light of the circumstances under which they are made, not misleading.


                                   ARTICLE 5

                                   COVENANTS

     5.1  TAXES.

          (a)  For purposes of this Agreement, the following terms shall have
the following meanings:
                                      20.
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<PAGE>
               (i)    "Taxes" means any net income, alternative or add-on
minimum tax, gross income, gross receipts, sales, goods and services, use, ad
valorem, franchise, profits, license, withholding, payroll, employment, excise,
severance, stamp, occupation, premium, real property, personal property, or
windfall profit tax, custom duty or other tax, governmental fee or other like
assessment or charge of any kind whatsoever, addition to tax or additional
amount imposed by any Taxing Authority responsible for the imposition of any
such tax (domestic or foreign), but only if and to the extent attributable to
periods (or partial periods) prior to and including the Effective Date, together
with any interest and any penalty thereon.

               (ii)   "Tax Return" means any return, report, information return,
registration form or other document (including any related or supporting
information) filed or required to be filed with any Taxing Authority in
connection with the determination of any Tax or the administration of any laws,
regulations or administrative requirements relating to any Tax.

               (iii)  "Taxing Authority" means, with respect to federal income
taxes, Revenue Canada and the Internal Revenue Service, and, with respect to any
other taxes, the applicable governmental body with the authority to audit and
collect such taxes.

          (b)  Subject to SECTIONS 7.6 and 7.7, and the conditions and
limitations contained therein, the Shareholders shall, jointly and severally,
indemnify and hold harmless Tetra Tech and TTC for all Taxes and expenses
(including reasonable accounting and legal fees and the costs and expenses of
enforcing such indemnification against the Shareholders) in connection with any
tax audit or proceeding, with respect to the operations of the Sentrex Companies
and Subsidiaries for all periods (or partial periods) prior to and including the
Closing Date, but not including those in connection with the transactions
contemplated by this Agreement.

          (c)  The covenants and agreements contained in this SECTION 5.1 and
all of the terms, covenants, warranties, representations and agreements
hereunder of the Shareholders related to federal and state taxes shall survive
the Closing until the expiration of the applicable statutory period of
limitation for the payment of such taxes, giving effect to any waiver,
mitigation or extension thereof (the "Tax Liability Period").

          (d)  Tetra Tech agrees that in the event it receives notice, whether
orally or in writing, of any federal, state, provincial or local examination,
claim, proposed adjustment or related matter with respect to any Tax Return for
Taxes covered by the Shareholders' indemnity in SECTION 5.1(b) (the "Tax
Controversies"), Tetra Tech shall timely notify the Shareholders' Agent (as
defined in SECTION 7.6).  Failure of Tetra Tech to timely notify the
Shareholders' Agent of any Tax Controversies shall not constitute a waiver of
any rights of Tetra Tech with respect to the indemnification thereof by the
Shareholders.  Any claim under this SECTION 5.1 shall be treated similarly to a
Third Party Claim under SECTION 7.7 hereof.
                                      21.
<PAGE>
<PAGE>

          (e)  After the Closing Date, each of the Shareholders shall:

               (i)    assist Tetra Tech in preparing any Tax Returns for periods
prior to the Closing Date;

               (ii)   cooperate fully in preparing for any audits of, or
disputes, contests or proceedings with, taxing authorities regarding any Tax
Returns which relate to the Sentrex Companies and Subsidiaries for periods prior
to the Closing Date;

               (iii)  make available to Tetra Tech and to any taxing authority
as reasonably requested all information, records and documents relating to tax
liabilities which are attributable to the businesses of the Sentrex Companies
and Subsidiaries relating to periods beginning prior to the Closing Date.

               (iv)   preserve all such information, records and documents until
the expiration of any applicable statutes of limitations or extensions thereof
and as otherwise required by law;

               (v)    make himself reasonably available, without charge, to
Tetra Tech, as reasonably requested, in connection with tax disputes related to
periods prior to the Closing Date; and

               (vi)   keep confidential any Tax information except as may
otherwise be necessary in connection with the filing of returns or claims for
refund or in conducting any audit or other Tax proceeding.

     5.2  STOCK OPTIONS.  On the Closing Date, Tetra Tech will grant incentive
stock options covering an aggregate of 100,000 shares of Tetra Tech Common Stock
to the key employees of the Sentrex Companies and the Subsidiaries as set forth
on a list to be provided by Leonard Stanmore that is approved by Tetra Tech.
The exercise price of each stock option will be the closing price of Tetra Tech
Common Stock on the Nasdaq Stock Market on the Closing Date.

     5.3  ELECTION UNDER SUBSECTION 85(1) OF THE INCOME TAX ACT (CANADA).  An
election under subsection 85(1) of the INCOME TAX ACT (Canada) (the "Act") must
be made and filed by each of the parties hereto in the form and manner and
within the time prescribed by the Act and Regulations made thereunder.  Such
elections shall specify that the deemed proceeds of disposition to each
Shareholder and the cost to TTC of the Shares (the "Agreed Amount") (A) shall
not be less than the greater of (i) the cost amount to the electing Shareholder
of its Shares and (ii) the non-share consideration received by such Shareholder
for such Shares and (B) shall not be greater than the fair market value to such
Shareholder of such Shares immediately before the Closing Date.  Subject to the
foregoing restrictions, the Agreed Amount for each election shall be as
determined by the electing Shareholder.  The Shareholders shall be responsible
for filing such elections, which shall be signed by Tetra Tech.

                                      22.
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<PAGE>

                                   ARTICLE 6

                                    CLOSING

     6.1  THE CLOSING.  The closing of purchase of the Shares (the "Closing")
shall occur on September 22, 1998 (the "Closing Date") at the offices of Lipman,
Zener & Waxman, 1220 Eglinton Avenue West, Toronto, Ontario, Canada M6C 2E3, or
at such other place mutually agreed to by the parties hereto.  At the Closing,
each of the parties shall take all such action and deliver all such documents,
instruments, certificates and other items as may be required, under this
Agreement or otherwise, in order to perform or fulfill all covenants and
agreements on its part to be performed or fulfilled at or prior to the Closing
Date.

     6.2  CLOSING DELIVERIES.

          (a)  DELIVERIES BY THE SHAREHOLDERS.  At the Closing, the Shareholders
will make the following deliveries to Tetra Tech:

               (i)    Stock certificates, duly endorsed for transfer and with
appropriate stock powers, sufficient to transfer good and marketable title to
the Shares to TTC, together with a certified copy of such resolutions as may be
necessary to permit the Shares to be duly and regularly transferred to and
registered in the name of TTC.

               (ii)   An opinion of counsel of Lipman, Zener & Waxman, counsel
for 1056584 Ltd., 1056585 Ltd., 946489 Ltd., CCC, SEI, VCL and the Shareholders,
dated the Closing Date and addressed to Tetra Tech, in substantially the form of
EXHIBIT 6.2A attached hereto.

               (iii)  An opinion of counsel of Hodgson, Russ, Andrews, Woods &
Goodyear LLP, counsel for Sentrex Electronics USA, Inc. and LAL, dated the
Closing Date and addressed to Tetra Tech, in substantially the form of EXHIBIT
6.2B attached hereto.

               (iv)   An Employment and Noncompetition Agreement in the form of
EXHIBIT 6.2C attached hereto (the "Employment and Noncompetition Agreements"),
signed by each of Raymond Conroy, Leonard Stanmore, Peter Nicoletti, James Suen,
Gordon Brooks and Andre Greco.

               (v)    A Registration Rights Agreement in the form of EXHIBIT
9.2E attached hereto (the Registration Rights Agreement"), signed by each of the
Shareholders.

               (vi)   Evidence satisfactory to Tetra Tech that all obligations
of the Sentrex Companies and the Subsidiaries to the Shareholders has been
forgiven or will be paid with the proceeds of the transactions contemplated by
this Agreement.

                                      23.
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<PAGE>

               (vii)  Evidence satisfactory to Tetra Tech that the management
agreements between (i) Cen-Comm Management and CCC, and (ii) Sentrex Management
and Sentrex Communication Systems Inc. have been terminated without cost to CCC
or Sentrex Communication Systems Inc.

               (viii) Evidence satisfactory to Tetra Tech that the assets of
946489 Ontario Limited, an Ontario corporation, have been transferred to SEI.

               (ix)   Such other documents as counsel for Tetra Tech may
reasonably request.

          (b)  DELIVERIES BY TETRA TECH.  At the Closing, Tetra Tech will make
the following deliveries to the Shareholders:

               (i)    A Certificate of the President of Tetra Tech and TTC,
dated the Closing Date, certifying that the resolutions attached to the
Certificate, which authorize and approve this Agreement and the transactions
contemplated herein, have been adopted by the Board of Directors of Tetra Tech
and TTC.

               (ii)   An opinion of Riordan & McKinzie, counsel for Tetra Tech,
dated the Closing Date and addressed to the Shareholders, in substantially the
form of EXHIBIT 6.2E attached hereto.

               (iii)  An opinion of McCarthy Tetrault, counsel for TTC, dated
the Closing Date and addressed to the Shareholders, in substantially the form of
EXHIBIT 6.2F attached hereto.

               (iv)   The Employment and Noncompetition Agreements, signed by
Tetra Tech.

               (v)    The Registration Rights Agreement, signed by Tetra Tech.

               (vi)   The consideration specified in SECTION 1.2 hereof.

               (vii)  Evidence satisfactory to the Shareholders that all
outstanding bank debt of the Sentrex Companies and Subsidiaries has been repaid.

               (viii) Such other documents as counsel for the Shareholders may
reasonably request.

     6.3  FURTHER ACTS.  If at any time after the Closing, any further action by
any of the parties to this Agreement is necessary or desirable to carry out the
purposes of this Agreement, such parties shall take all such necessary or
desirable action or use such parties' commercially reasonable efforts to cause
such action to be taken.
                                      24.

<PAGE>
<PAGE>
                                   ARTICLE 7

                    SURVIVAL OF REPRESENTATIONS, WARRANTIES
               COVENANTS AND RELATED AGREEMENTS; INDEMNIFICATION

     7.1  GENERAL LIABILITY PERIOD.  All of the terms, covenants, warranties,
representations and agreements made by the Shareholders in this Agreement, or in
any document, certificate, schedule or instrument delivered in connection
herewith shall survive the Closing and shall continue in effect, notwithstanding
any investigation by or on behalf of the Purchaser, for a period of 18 months
after the Closing Date (as specified, the "General Liability Period").

     7.2  TAX LIABILITY PERIOD.  The Tax Liability Period shall be as described
in SECTION 5.1 hereof.

     7.3  SURVIVAL OF THE TETRA TECH'S AND TTC'S OBLIGATIONS.  All the terms,
covenants, warranties, representations and agreements made by Tetra Tech and TTC
in this Agreement or in any document, certificate, schedule or instrument
delivered in connection herewith shall survive the Closing and shall continue in
effect, notwithstanding any investigation by or on behalf of the Shareholders.

     7.4  INDEMNITY BY THE SHAREHOLDERS

          (a)  Except as otherwise provided in this ARTICLE 7, the Shareholders
shall jointly and severally indemnify and hold harmless Tetra Tech and TTC and
the officers, directors, agents, affiliates and representatives of Tetra Tech
and TTC or any of them (the "Purchaser Indemnitees") from and against, and shall
reimburse the Purchaser Indemnitees on demand for any loss, liability, damage or
expense that the Purchaser Indemnitees shall incur or suffer, but subject at all
times to SECTION 7.6 hereof (collectively, "Purchaser's Recoverable Losses"),
resulting from any breach by the Shareholders of any (i) representation or
warranty contained in ARTICLE 2 hereof; (ii) agreement or covenant under or
pursuant to this Agreement; or (iii) document, certificate, schedule or
instrument delivered by or on behalf of the Shareholders pursuant hereto
(collectively with respect to which a claim for Purchaser's Recoverable Losses
is  made by the Purchaser Indemnitees during the General Liability Period or Tax
Liability Period, as applicable, hereinafter referred to as a "Shareholders
Agreement Breach").  Provided that with respect to the following, the
Shareholders shall jointly and severally indemnify and hold harmless the
Purchaser Indemnitees from and against, and shall reimburse the Purchaser
Indemnitees on demand for, 50% of all Purchaser's Recoverable Losses resulting
from (i) any personnel practices engaged in by LAL on behalf of Whalen/Sentrex
LLC prior to the Closing Date, including but not limited to any violations of
the immigration, labor, employment, criminal or other laws of the United States;
or (ii) any determination that Tetra Tech is, or was in the past, an employer or
joint employer of any persons engaged, hired or retained by LAL on behalf of
Whalen/Sentrex LLC to perform
                                      25.
<PAGE>
<PAGE>
duties for, on behalf of, or at the direction of, any United States or foreign
entity now or previously owned in whole or in part by any Shareholder, any
Sentrex Company or any Subsidiary.

          (b)  Each Shareholder shall severally indemnify and hold harmless the
Purchaser Indemnitees from and against, and shall reimburse the Purchaser
Indemnitees on demand for any of Purchaser's Recoverable Losses resulting from,
any misrepresentation by such Shareholder or breach by such Shareholder of any
representation or warranty made by such Shareholder contained in ARTICLE 3
hereof.

     7.5  INDEMNITY BY THE PURCHASER.  Tetra Tech shall indemnify and hold
harmless the Shareholders, their heirs, personal representatives, successors and
assigns (the "Shareholders Indemnitees") from and against, and shall reimburse
the Shareholders Indemnitees on demand for any loss, liability, damage or
expense, including reasonable attorneys' fees and cost of investigation incurred
as a result thereof, that the Shareholders Indemnitees shall incur or suffer
(collectively, the "Shareholders' Recoverable Losses") resulting from any breach
by Tetra Tech and TTC of any (i) representation or warranty contained in ARTICLE
4 hereof, (ii) agreement or covenant under or pursuant to this Agreement or
(iii) document, certificate, schedule or instrument delivered by or on behalf of
Tetra Tech and TTC in connection herewith (collectively with respect to which a
claim for the Shareholders' Recoverable Losses is made by the Shareholders
Indemnitees during the General Liability Period hereinafter referred to as a
"Purchaser Agreement Breach").

     7.6  LIMITATIONS ON RECOVERABLE LOSSES.  Notwithstanding anything to the
contrary, express or implied, set forth herein, claims for payment of the
Purchaser's Recoverable Losses in respect of a Shareholders Agreement Breach or
breach of SECTION 7.4(b), (a) may be made only with respect to claims arising
during the General Liability Period or the Tax Liability Period, as applicable;
(b) must be made, if at all, by giving the written Claim Notice (as defined in
SECTION 7.7(a) hereof) during the General Liability Period or Tax Liability
Period, as applicable, with respect to such claim; and (c) may be made only to
the extent that the aggregate amount of the Purchaser's Recoverable Losses
exceeds $50,000, in which case all the Purchaser's Recoverable Losses in excess
of $50,000 which are covered by CLAUSES (a) and (b) hereinabove shall be paid by
the Shareholders; and (d) solely with respect to each of Gordon Brooks and Andre
Greco, shall not exceed the aggregate consideration received by each such
Shareholder pursuant to SECTION 1.2 hereof.  Notwithstanding anything to the
contrary, express or implied, set forth herein, claims for payment of the
Shareholders' Recoverable Losses in respect of a Purchaser Agreement Breach (a)
may be made only with respect to claims arising during the General Liability
Period and (b) must be made, if at all, by giving written Claim Notice during
the General Liability Period or Tax Liability Period, as applicable, with
respect to such claim.
                                      26.
<PAGE>
<PAGE>
     7.7  CLAIMS FOR INDEMNIFICATION; DISPUTES.

          (a)  CLAIMS FOR INDEMNIFICATION.  Any person entitled to
indemnification hereunder (individually or with others, collectively, the
"Indemnitee") shall give Leonard Stanmore, as agent for the Shareholders (the
"Shareholders' Agent") or Tetra Tech, as the case may be (the "Indemnitor"),
written notice (the "Claim Notice") of any claim (including the receipt of any
demand) or the commencement of any action with respect to which indemnity may be
sought by the Indemnitee (individually, a "Claim" and collectively, the
"Claims"); PROVIDED, HOWEVER, that if the Indemnitee fails to give such Claim
Notice prior to the expiration of the General Liability Period or Tax Liability
Period, as applicable, all rights of the Indemnitee to assert any such Claims
for a Purchaser Agreement Breach or Shareholders Agreement Breach or breach of
SECTION 7.4(b), as the case may be, shall terminate and be forever waived.  The
Claim Notice shall state (i) the aggregate amount of the Purchaser's Recoverable
Losses or the Shareholders' Recoverable Losses (in either case, "Recoverable
Losses") as to which indemnification is being sought (which amount may be
estimated and updated from time to time); (ii) the components of the amount of
Recoverable Losses for which indemnification is being sought (which components
may be estimated and updated from time to time); and (iii) the specific grounds
upon which the Claim for indemnification is being made.  The Claims Notice shall
be given within ten (10) business days after the Indemnitee is notified of the
Claim.  The right of the Indemnitee to indemnification for a Claim shall be
deemed to be accepted by the Indemnitor unless, within 30 days after the
Indemnitor's receipt of the Claim Notice, the Indemnitor shall notify the
Indemnitee in writing that it objects in whole or in part to the right of the
Indemnitee to indemnification with respect to the Claim.

          (b)  CONTROL OF LITIGATION; MUTUAL COOPERATION.  If a Claim is based
upon a claim asserted by a third party against the Indemnitee (a "Third Party
Claim") and the Indemnitor objects in whole to the right of the Indemnitee to
indemnification with respect to the Claim, the Indemnitee shall be entitled to
control the defense of the Third Party Claim, including, without limitation, the
employment of counsel and the right to settle the Third Party Claim without any
participation by or consent from the Indemnitor.  All fees and expenses of
counsel retained by the Indemnitee to defend such Third Party Claim, expert
witness fees and other costs incurred in such action, shall be payable by the
Indemnitee defending such Third Party Claim; PROVIDED, HOWEVER, that if such
Third Party Claim results in a Recoverable Loss for which the Indemnitor,
notwithstanding any denial of liability, is found to be liable hereunder, such
reasonable fees and expenses of counsel, expert witness fees and other
reasonable costs incurred in such action shall be deemed to be included in such
Recoverable Loss and payable by the Indemnitor to the extent and under the
limitations provided in this ARTICLE 7.  If the Indemnitor does not object in
whole to the right of the Indemnitee to indemnification with respect to the
Claim, the Indemnitor shall be entitled, in his or its discretion, to assume the
defense of the Third Party Claim, including, without limitation, the employment
of counsel reasonably satisfactory to the Indemnitee.  If the Indemnitor does
not object in whole to the right of the Indemnitee to indemnification with
respect to the Claim, but does not elect to assume the defense of the Third
Party Claim, the Indemnitee shall be entitled to assume the defense of the Third
Party Claim.  Regardless of which party is controlling the
                                      27.
<PAGE>
<PAGE>
defense of the Third Party Claim for which the Indemnitor admits liability
hereunder, (i) the Indemnitor and the Indemnitee shall act in good faith; (ii)
no settlement of the Third Party Claim may be agreed to without the written
consents of the Indemnitor and the Indemnitee, which consents shall not be
unreasonably withheld or delayed; (iii) the reasonable fees and expenses of
counsel retained to defend the Third Party Claim, expert witness fees and other
costs incurred in such action shall be deemed to be included in such Recoverable
Losses and shall be payable by the Indemnitor to the extent and under the
limitations provided in this ARTICLE 7; and (iv) the party controlling the
defense of the Third Party Claim shall deliver, or cause to be delivered, to the
other party copies of all correspondence, pleading, motions, briefs, appeals or
other written statements relating to or submitted in connection with the defense
of the Third Party Claim, and timely notices of, and the right to participate in
(as an observer), any hearing or other court proceeding relating to the Third
Party Claim.

          (c)  RESOLUTION OF DISPUTES.  The Indemnitor and the Indemnitee shall
undertake in good faith to or to have their representatives promptly meet and
attempt to resolve all disputes regarding indemnification.  If the Indemnitor
and the Indemnitee are unable to resolve such disputes within 20 days after the
Claims Notice, the resolution of the disputes shall be referred to and settled
by arbitration to be held in Denver, Colorado and conducted in accordance with
the then current Commercial Arbitration Rules of the American Arbitration
Association.  Judgment upon the award may be entered in any court of competent
jurisdiction or application may be made to such court for a judicial acceptance
of the award and an order of enforcement, as the case may be.  The successful or
prevailing party or parties shall be entitled to recover all attorneys' fees,
expert witness fees and other costs incurred in such action, in addition to any
other relief to which it or they may be entitled.  Such attorneys' fees, expert
witness fees and other costs shall be payable in cash.

     7.8  INDEMNITY AS EXCLUSIVE REMEDY.  Each party hereto acknowledges and
agrees that, from and after the Closing Date, its sole and exclusive remedy with
respect to any and all claims relating to the subject matter of this Agreement
shall be pursuant to the indemnification provisions set forth in this ARTICLE 7,
except that nothing in this Agreement shall be deemed to constitute a waiver of
any tort claims of, or causes of action arising from, intentionally fraudulent
misrepresentation or deceit, and except that with respect to claims covered by
insurance, such insurance proceeds (to the extent of policy limits) shall be the
sole and exclusive remedy.  In furtherance of the foregoing, each party hereto
waives, from and after the Closing Date, to the fullest extent permitted under
applicable law, any and all claims, rights and causes of action (other than tort
claims of, or causes of action arising from, intentionally fraudulent
misrepresentation or deceit, and claims arising under this ARTICLE 7) it may
have relating to the subject matter of this Agreement arising under or based
upon any Canadian, United States, state, provincial, or local statute, law,
ordinance, rule or regulation or otherwise.

     7.9  ASSIGNMENT OF CLAIMS.  Upon satisfaction of an obligation to indemnify
hereunder, and in consideration thereof, the Indemnitor shall automatically be
assigned any and all rights, claims, causes of action and demands of whatever
kind and nature which the
                                      28.
<PAGE>
<PAGE>
Indemnitee may have against any person, firm or entity giving rise or relating
to such Claims. Specifically, but in not in limitation of the foregoing, Tetra
Tech shall assign uncollected accounts receivable to the Shareholders to the
extent that a Claim hereunder is based upon a breach of the representation and
warranty set forth in SECTION 2.12 hereof.  The Indemnitee shall cooperate so
that all such rights vest fully in the Indemnitor and shall cooperate in any
efforts of the Indemnitor to recover.


                                   ARTICLE 8

                               GENERAL PROVISIONS

     8.1  ENTIRE AGREEMENT; MODIFICATIONS; WAIVER.  This Agreement supersedes
any and all agreements heretofore made relating to the subject matter hereof,
and constitutes the entire agreement of the parties relating to the subject
matter hereof.  This Agreement may be amended only by an instrument in writing
signed by each of the parties hereto.  Inspection of documents or the receipt of
information pursuant to this Agreement shall not constitute a waiver of any
representation, warranty, covenant or condition hereunder.  No waiver shall be
binding unless executed in writing by the party making such waiver.

     8.2  SEVERABILITY.  If any clause or provision of this Agreement shall be
held invalid or unenforceable by the final determination of a court of competent
jurisdiction, and all appeals therefrom shall have failed or the time for such
appeals shall have expired, such clause or provision shall be deemed eliminated
from this Agreement but the remaining provisions shall nevertheless be given
full force and effect.

     8.3  SUCCESSORS AND ASSIGNS.  This Agreement shall be binding upon and
inure to the benefit of each of the parties hereto, and their respective
successors and assigns.

     8.4  COUNTERPARTS.  This Agreement may be executed in several counterparts,
each of which shall be deemed an original, and all of which together shall
constitute one and the same instrument.

     8.5  GOVERNING LAW.  This Agreement shall be construed and interpreted in
accordance with the internal substantive laws of the State of California.

     8.6  NOTICES.  All notices required or desired to be given hereunder shall
be given in writing and signed by the party so giving notice, and shall be
effective when personally delivered, one business day after transmission if sent
by facsimile and appropriate confirmation is received, or five (5) days after
being deposited in the United States or Canadian mail, as certified or
registered mail, return receipt requested, first class postage and fees prepaid,
addressed as set forth below.  Any party from time to time may change such
party's address for giving notice by giving notice thereof in the manner
outlined above:
                                      29.
<PAGE>
<PAGE>
          If to Tetra Tech:

               Tetra Tech, Inc.
               630 N. Rosemead Boulevard
               Pasadena, California  91107-2190
               Attention:  Li-San Hwang
               Facsimile:  (626) 351-1188

          With a copy to:

               Riordan & McKinzie
               300 South Grand Avenue, 29th Floor
               Los Angeles, California  90071
               Attention:  Janis B. Salin, Esq.
               Facsimile:  (213) 229-5024

          If to the Shareholders:

          at the addresses listed under their respective signatures
          on the signature pages of this Agreement.

          With a copy to:

               Lipman, Zener & Waxman
               1220 Eglinton Avenue West
               Toronto, Ontario
               Canada, M6C 2E3
               Attention:  Allan L. Lipman, Esq.
               Facsimile:  (416) 789-9015


     8.7  EXPENSES.  The Shareholders will pay, or cause the Sentrex Companies
to pay, their fees and expenses, and Tetra Tech will pay its own fees and
expenses, and those of TTC incurred in connection with this Agreement or any
transaction contemplated by this Agreement.

     8.8  CONFIDENTIALITY.  From and after the date hereof, the parties shall
not disclose or communicate to any person, firm or corporation in any manner
whatsoever any Confidential Information (as defined below) of the other, which
any party learns, discovers or otherwise acquires pursuant to this Agreement and
the transactions contemplated hereunder; PROVIDED, HOWEVER, that the parties
shall be permitted to make such disclosures or communications to their financial
advisors, consultants, attorneys, accountants and lenders provided that such
Confidential Information shall be accompanied by directions that such
information is to remain confidential in accordance with the provisions
contained herein.  The term "Confidential Information," as used herein, means
all information of a business or technical nature relative to
                                      30.
<PAGE>
<PAGE>
Tetra Tech, the Sentrex Companies' and the Subsidiaries' businesses currently
being conducted by Tetra Tech, the Sentrex Companies and the Subsidiaries.  Said
term shall not include information (i) which is or becomes so generally known as
to be part of the public domain, (ii) which is lawfully received from a third
party, without restriction, (iii) which was known by Tetra Tech or the Sentrex
Companies or Subsidiaries without restriction on disclosure prior to receipt
from the other party or (iv) which is independently developed by persons who had
no access to the Confidential Information, or (v) which is disclosed pursuant to
subpoena, court order or similar legal process where the party whose
Confidential Information is to be disclosed has had a reasonable opportunity to
appear and object to disclosure.

     8.9  TIME.  Time is of the essence in the performance of the parties'
respective obligations herein contained.

     8.10 NO THIRD PARTIES BENEFITTED.  This Agreement is made and entered into
for the sole protection and benefit of the parties hereto, their successors and
assigns, and no other person or persons shall have any right or action under
this Agreement.

     8.11 RECITALS, SCHEDULES AND EXHIBITS.  The recitals, schedules and
exhibits to this Agreement are incorporated herein and, by this reference, made
a part hereof as if fully set forth at length herein.

     8.12 SECTION HEADINGS.  The section headings used herein are inserted for
reference purposes only and shall not in any way affect the meaning or
interpretation of this Agreement.

     8.13 SHAREHOLDERS' AGENT.  For purposes of this Agreement, Tetra Tech shall
be entitled to rely on the actions of the Shareholders' Agent, as representative
of the Shareholders, without independent investigation of the authority of
Shareholders' Agent.
                                      31.
<PAGE>
<PAGE>
     8.14 DOLLAR REFERENCES.  Except as otherwise noted, all references to
dollar ($) amounts in this Agreement shall be deemed to refer to United States
Dollars.

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


                                   SHAREHOLDERS:


                                   _____________________________________
                                   Raymond Conroy
                         Address:  303 Dods Crescent
                                   Alton, Ontario
                                   L0N 1A0
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   Elizabeth Stanmore
                         Address:  26 Grand Oaks Crescent
                                   Brampton, Ontario
                                   L6Z 3K7
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   Leonard Stanmore
                         Address:  26 Grand Oaks Crescent
                                   Brampton, Ontario
                                   L6Z 3K7
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   Peter Nicoletti
                         Address:  101 Flushing Avenue
                                   Woodbridge, Ontario
                                   L4L 3H9
                                   Facsimile:  (905) 459-9686
                                      32.
<PAGE>
<PAGE>



                                   _____________________________________
                                   Silvana Nicoletti
                         Address:  101 Flushing Avenue
                                   Woodbridge, Ontario
                                   L4L 3H9
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   James Suen
                         Address:  5812 Fieldon Road
                                   Mississauga, Ontario
                                   L5M 5K1
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   Gordon Brooks
                         Address:  520 Fralicks Beach Road
                                   Port Perry, Ontario
                                   L9L 1B6
                                   Facsimile:  (905) 459-9686


                                   _____________________________________
                                   Andre Greco
                         Address:  3472 Church Street
                                   Blackstock, Ontario
                                   L0B 1B0
                                   Facsimile:  (905) 459-9686
                                      33.
<PAGE>
<PAGE>

                                   TETRA TECH, INC.


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


                                   TETRA TECH CANADA LTD.


                                   By:  ______________________________
                                        Li-San Hwang
                                        President
                                           34.

<PAGE>
<PAGE>
                                                               EXHIBIT 1.2A

     The Exchangeable Shares shall have the following rights, privileges,
restrictions and conditions:

                                   ARTICLE 1
                                 INTERPRETATION

1.1  DEFINITIONS

     In these Exchangeable Share Provisions, unless something in the subject
matter or context is inconsistent therewith:

     "BOARD OF DIRECTORS" means the board of directors of the Corporation.

     "BUSINESS DAY" means any day other than a Saturday, a Sunday or a day when
banks are not open for business in Toronto, Ontario.

     "CANADIAN DOLLAR EQUIVALENT" means in respect of an amount expressed in a
foreign currency (the "Foreign Currency Amount") at any date the product
obtained by multiplying (a) the Foreign Currency Amount by (b) the official noon
spot exchange rate on such date for such foreign currency as reported by the
Bank of Canada or, in the event such spot exchange rate is not available, such
exchange rate on such date for such foreign currency as may be deemed by the
Board of Directors to be appropriate for such purpose.

     "COMMON SHARES" means the Common Shares of the Corporation.

     "CORPORATION" means Tetra Tech Canada Ltd., a corporation existing under
the laws of the Province of Ontario.

     "CURRENT MARKET PRICE" means, in respect of a Tetra Tech Common Share on
any date, the Canadian Dollar Equivalent of the average trading price for the 5
day period preceding that date of the Tetra Tech Common Shares on the exchange
on which it principally trades.

     "DIVIDEND AMOUNT" means an amount equal to the full amount of all dividends
and distributions declared and unpaid on each Exchangeable Share and all
dividends and distributions declared on a Tetra Tech Common Share that have not
been declared on each Exchangeable Share in accordance with Section 2.1, in each
case with a record date prior to the Liquidation Date, Retraction Date or
Exchange Date, as applicable.

     "EXCHANGE DATE" has the meaning set out in Section 5.2.

     "EXCHANGE RIGHT" has the meaning set out in Section 4.1.

     "EXCHANGEABLE SHARE PROVISIONS" means the rights, privileges, restrictions
and conditions set out in these articles of incorporation.

     "EXCHANGEABLE SHARES" mean the Exchangeable Shares of the Corporation to
which are attached the Exchangeable Share Provisions.

     "LIQUIDATION AMOUNT" has the meaning set out in Section 3.1(a).
<PAGE>
<PAGE>
     "LIQUIDATION DATE" has the meaning set out in Section 3.1(a).

     "OBCA" means the Business Corporations Act (Ontario), as amended.

     "RETRACTED SHARES" has the meaning set out in Section 4.1(a).

     "RETRACTION CALL PURCHASE PRICE" has the meaning set out in Section 4.2(a).

     "RETRACTION CALL RIGHT" has the meaning set out in Section 4.2(a).

     "RETRACTION DATE" has the meaning set out in Section 4.1(a).

     "RETRACTION PRICE" has the meaning set out in Section 4.1(a).

     "RETRACTION REQUEST" has the meaning set out in Section 4.1(a).

     "SUPPORT AGREEMENT" means that agreement executed by Tetra Tech and the
Corporation on September 22, 1998.

     "TETRA TECH COMMON SHARES" means shares of common stock, par value $.01, of
Tetra Tech and any other securities into which such shares may be changed or for
which such shares may be exchanged (whether or not Tetra Tech shall be the
issuer of such other securities) or any other consideration which may be
received by the holders of such shares, pursuant to a recapitalization,
reconstruction, reorganization or reclassification of, or amalgamation, merger,
liquidation or similar transaction, affecting such shares.

     "TETRA TECH" means Tetra Tech, Inc. a corporation existing under the laws
of the State of Delaware.


                                   ARTICLE 2
                                   DIVIDENDS

2.1  DIVIDENDS

     A holder of an Exchangeable Share shall be entitled to receive and the
Board of Directors shall, subject to applicable law, on each date a dividend is
declared on a Tetra Tech Common Share, declare a dividend on each Exchangeable
Share (a) in the case of a cash dividend or distribution declared on the Tetra
Tech Common Shares, in an amount in cash for each Exchangeable Share as is equal
to the Canadian Dollar Equivalent on the said date of the cash dividend or
distribution declared on each Tetra Common Share, (b) in the case of a stock
dividend or distribution declared on the Tetra Tech Common Shares to be paid in
Tetra Tech Common Shares, in such number of Exchangeable Shares for each
Exchangeable Share as is equal to the number of Tetra Tech Common Shares to be
paid on each Tetra Tech Common Share or (c) in the case of a dividend or
distribution declared on the shares of Tetra Tech Common Shares to be paid in
property other than cash or shares of Tetra Tech Common Shares, in such type and
amount of property for each Exchangeable Share as is the same as or economically
equivalent to the type and amount of property declared as a dividend or
distribution on each Tetra Tech Common Share.
<PAGE>
<PAGE>
Such dividends or distributions shall be paid out of the assets of the
Corporation properly applicable to the payment of dividends, or out of
authorized but unissued shares or other securities of the Corporation.

2.2  PAYMENT OF DIVIDENDS

     Cheques of the Corporation payable at par at any branch of the bankers of
the Corporation shall be issued in respect of any cash dividends or
distributions contemplated hereby and the sending of such a cheque to each
holder of an Exchangeable Share shall satisfy the cash dividend represented
thereby unless the cheque is not paid on presentation. Certificates registered
in the name of the registered holder of Exchangeable Shares shall be issued or
transferred in respect of any stock dividends or other distribution of
Exchangeable Shares contemplated by Section 2.1(b) hereof and the sending of
such a certificate to each holder of an Exchangeable Share shall satisfy the
stock dividend or other distribution of Exchangeable Shares represented thereby.
Such other type and amount of property in respect of any dividends or
distributions contemplated by Section 2.1(c) hereof shall be issued, distributed
or transferred by the Corporation in such manner as it shall determine and the
issuance, distribution or transfer thereof by the Corporation to each holder of
an Exchangeable Share shall satisfy the dividend or distribution represented
thereby. No holder of an Exchangeable Share shall be entitled to recover by
action or other legal process against the Corporation any dividend that is
represented by a cheque that has not been duly presented to the Corporation's
bankers for payment or that otherwise remains unclaimed for a period of six
years from the date on which such dividend or distribution was payable.

2.3  RECORD AND PAYMENT DATES

     The record date for the determination of the holders of Exchangeable Shares
entitled to receive payment of, and the payment date for, any dividend or
distribution declared on the Exchangeable Shares under Section 2.1 hereof shall
be the same as the record date and payment date, respectively, for the
corresponding dividend or distribution declared on the Tetra Tech Common Shares.

2.4  PARTIAL PAYMENTS

     If on any payment date for any dividends or distributions declared on the
Exchangeable Shares under Section 2.1 hereof the dividends or distributions are
not paid in full on all of the Exchangeable Shares then outstanding, any such
dividends or distributions that remain unpaid shall be paid on a subsequent date
or dates determined by the Board of Directors on which the Corporation shall
have sufficient money or other assets properly applicable to the payment of such
dividends or distributions.


                                   ARTICLE 3
                                  LIQUIDATION

3.1  PARTICIPATION UPON LIQUIDATION, DISSOLUTION OR WINDING UP OF THE
CORPORATION
<PAGE>
<PAGE>
     (a)  In addition to any other approval required by law, any voluntary
liquidation, dissolution or winding up of the Corporation or any other
distribution of the assets of the Corporation among its shareholders for the
purpose of winding up its affairs shall be subject to the approval of the
holders of the Exchangeable Shares.

     (b)  Subject to applicable law, in the event of the liquidation,
dissolution or winding up of the Corporation or any other distribution of the
assets of the Corporation among its shareholders for the purpose of winding up
its affairs (the effective date thereof being referred to herein as the
"Liquidation Date"), a holder of an Exchangeable Share shall be entitled to
exercise its Exchange Right, which shall be satisfied in full by the delivery to
such holder one Tetra Tech Common Share, plus (b) the Dividend Amount, if any
(collectively, the "Liquidation Amount").

     (c)  In the case of a distribution on Exchangeable Shares under this
Section 3.1, on or promptly after the Liquidation Date, the Corporation shall
cause to be delivered to the holders of the Exchangeable Shares the Liquidation
Amount for each such Exchangeable Share upon presentation and surrender of the
certificates representing such Exchangeable Shares, together with such other
documents and instruments as may be required to effect a transfer of
Exchangeable Shares under the OBCA and such additional documents as the
Corporation may reasonably require, at the registered office of the Corporation.
Payment of the aggregate Liquidation Amount for such Exchangeable Shares shall
be made by delivery to each holder, at the address of the holder recorded in the
securities register of the Corporation for the Exchangeable Shares or by holding
for pick-up by the holder at the registered office of the Corporation,
certificates representing the aggregate number of Tetra Tech Common Shares
deliverable by the Corporation to such holder (which shares shall be duly issued
as fully paid and non-assessable and shall be free and clear of any lien, claim,
encumbrance, security interest or adverse claim) and a cheque of the Corporation
payable at par at any branch of the bankers of the Corporation in payment of the
remaining portion, if any, of the aggregate Liquidation Amount payable to such
holder. On or before the Liquidation Date, the Corporation shall deposit or
cause to be deposited the total Liquidation Amount in respect of the
Exchangeable Shares in a custodial account with any chartered bank or trust
company in Canada named in such notice. Upon such deposit being made, the rights
of the holders of Exchangeable Shares as such shall be limited to receiving
their proportionate part of the total Liquidation Amount for such Exchangeable
Shares so deposited, against presentation and surrender of the said certificates
held by them, respectively, in accordance with the foregoing provisions and any
interest allowed on such deposit shall belong to the Corporation. Upon such
payment or deposit of the total Liquidation Amount, the holders of the
Exchangeable Shares shall thereafter be considered and deemed for all purposes
to be the holders of the Tetra Tech Common Shares delivered to them.

     (d)  After the Corporation has satisfied its obligations to pay the holders
of the Exchangeable Shares the total Liquidation Amount pursuant to this Section
3.1, such holders shall not be entitled to share in any further distribution of
the assets of the Corporation.
<PAGE>
<PAGE>
                                   ARTICLE 4
                         RETRACTION AT OPTION OF HOLDER

4.1  RETRACTION AT OPTION OF HOLDER

     (a)  Subject to applicable law and the due exercise by Tetra Tech of a
Retraction Call Right, a holder of Exchangeable Shares shall be entitled at any
time after five months from the date of issue of the Exchangeable Shares to
require the Corporation to redeem, on the fifth Business Day after the date on
which the Retraction Request is received by the Corporation (the "Retraction
Date"), all or any part of the Exchangeable Shares registered in the name of
such holder for an amount per share equal to (a) the Current Market Price of a
share of Tetra Tech Common Shares on the last Business Day prior to the
Retraction Date, which shall be satisfied in full by the Corporation causing to
be delivered to such holder one Tetra Tech Common Share for each Exchangeable
Share presented and surrendered by the holder, plus (b) the Dividend Amount, if
any (collectively, the "Retraction Price"), provided that the Retraction Price
shall only apply so long as the Exchangeable Shares are held by any holder other
than Tetra Tech.  To effect a redemption under this Section 4.1, the holder must
present and surrender at the registered office of the Corporation the
certificate representing the Exchangeable Shares that the holder desires to have
the Corporation redeem, together with such other documents and instruments as
may be required to effect a transfer of Exchangeable Shares under the OBCA and
such additional documents and instruments as the Corporation may reasonably
require, together with a duly executed statement (the "Retraction Request") in
the form of Schedule A hereto or in such other form as may be acceptable to the
Corporation specifying that the holder desires to have all or any number
specified therein of the Exchangeable Shares represented by such certificate
(the "Retracted Shares") redeemed by the Corporation.

     (b)  In the case of a redemption of Exchangeable Shares under this Section
4.1, upon receipt by the Corporation of a certificate representing the number of
Exchangeable Shares which the holder desires to have the Corporation redeem,
together with a Retraction Request, and provided that the Retraction Request is
not revoked by the holder in the manner specified in Section 4.1(5), the
Corporation shall redeem the Retracted Shares effective at the close of business
on the Retraction Date.  On the Retraction Date, the Corporation shall deliver
to the relevant holder, at the address of the holder recorded in the securities
register of the Corporation for the Exchangeable Shares or at the address
specified in the holder's Retraction Request or by holding for pick-up by the
holder at the registered office of the Corporation, (i) a certificate
representing the number of Tetra Tech Common Shares to which such holder is
entitled (which shares shall be duly issued as fully paid and non-assessable and
shall be free and clear of any lien, claim, encumbrance, security interest or
adverse claim) registered in the name of the holder or in such other name as the
holder may request in payment of the Retraction Price, (ii) a cheque of the
Corporation payable at par at any branch of the bankers of the Corporation in
payment of the remaining portion, if any, of the aggregate Retraction Price to
which such holder is entitled and (iii) if a part only of the Exchangeable
Shares represented by any certificate are redeemed a new certificate, at the
expense of the Corporation, for the balance.
<PAGE>
<PAGE>
Such delivery of a certificate for Tetra Tech Common Shares and a cheque by the
Corporation shall be deemed to be payment of and shall satisfy and discharge all
liability for the Retraction Price to the extent that the same is represented by
such share certificates and cheque, unless such cheque is not paid on due
presentation.

     (c)  On and after the close of business on the Retraction Date, the holder
of the Retracted Shares shall cease to be a holder of such Retracted Shares and
shall not be entitled to exercise any of the rights of a holder in respect
thereof, other than the right to receive its proportionate part of the aggregate
Retraction Price for such Retracted Shares, unless upon presentation and
surrender of certificates in accordance with the foregoing provisions, payment
of the aggregate Retraction Price payable to such holder shall not be made, in
which case the rights of such holder shall remain unaffected until such
aggregate Retraction Price has been paid in the manner hereinbefore provided. On
and after the close of business on the Retraction Date, provided that
presentation and surrender of certificates and payment of such aggregate
Retraction Price has been made in accordance with the foregoing provisions, the
holder of the Retracted Shares so redeemed by the Corporation shall thereafter
be considered and deemed for all purposes to be a holder of Tetra Tech Common
Shares delivered to such holder.

     (d)  Notwithstanding any other provision of this Section 4.1, the
Corporation shall not be obligated to redeem Retracted Shares specified by a
holder in a Retraction Request to the extent that such redemption of Retracted
Shares would be contrary to solvency requirements or other provisions of
applicable law. If the Corporation believes that on any Retraction Date it would
not be permitted by any of such provisions to redeem the Retracted Shares
tendered for redemption on such date, and Tetra Tech shall not have exercised
its Retraction Call Right with respect to the Retracted Shares, the Corporation
shall only be obligated to redeem Retracted Shares specified by a holder in a
Retraction Request to the extent of the maximum number that may be so redeemed
(rounded down to a whole number of shares) as would not be contrary to such
provisions and shall notify the holder at least two Business Days prior to the
Retraction Date as to the number of Retracted Shares which will not be redeemed
by the Corporation. In any case in which the redemption by the Corporation of
Retracted Shares would be contrary to solvency requirements or other provisions
of applicable law and more than one holder has delivered a Retraction Request,
the Corporation shall redeem Retracted Shares in accordance with Section 4.1(2)
on a pro rata basis and shall issue to each such holder of Retracted Shares a
new certificate, at the expense of the Corporation, representing the Retracted
Shares not redeemed by the Corporation.

     (e)  A holder of Retracted Shares may, by notice in writing given by the
holder to the Corporation before the close of business on the Business Day
immediately preceding the Retraction Date, withdraw its Retraction Request in
which event such Retraction Request shall be null and void.
<PAGE>
<PAGE>
4.2  RETRACTION CALL RIGHTS

     (a)  In the event that a holder of Exchangeable Shares delivers a
Retraction Request pursuant to Section 4.1 and subject to the limitations set
forth in Section 4.2(2), Tetra Tech shall have the overriding right (a
"Retraction Call Right"), notwithstanding the proposed redemption of the
Exchangeable Shares by the Corporation pursuant to Section 4.1 hereof, to
purchase from such holder on the Retraction Date all but not less than all of
the Retracted Shares held by such holder on payment by Tetra Tech of an amount
per share equal to the Retraction Price (the "Retraction Call Purchase Price").
In the event of the exercise of a Retraction Call Right, a holder of
Exchangeable Shares who has delivered a Retraction Request shall be obligated to
sell all the Retracted Shares to Tetra Tech on the Retraction Date on payment by
Tetra Tech of an amount per share equal to (a) the Current Market Price of the
Tetra Tech Common Shares on the last Business Day prior to the Retraction Date,
which shall be satisfied in full by Tetra Tech causing to be delivered to such
holder one Tetra Tech Common Share for each Exchangeable Share presented and
surrendered by the holder, plus (b) the Dividend Amount, if any.

     (b)  Upon receipt by the Corporation of a Retraction Request, the
Corporation shall immediately notify Tetra Tech thereof.  In order to exercise
its Retraction Call Right, Tetra Tech must notify the Corporation in writing of
its determination to do so (an "Tetra Tech Call Notice") within two Business
Days of notification by the Corporation of the receipt by the Corporation of the
Retraction Request. If Tetra Tech so notifies the Corporation within such two
Business Day period, the Corporation shall notify the holders of Exchangeable
Shares as soon as possible thereafter as to the exercise of a Retraction Call
Right. If Tetra Tech delivers an Tetra Tech Call Notice within such two Business
Day period and duly exercises its Retraction Call Right in accordance with this
Section 4.2, the obligation of the Corporation to redeem the Retracted Shares
shall terminate and, provided that the Retraction Request is not revoked by the
holder in the manner specified in Section 4.1(5), Tetra Tech shall purchase from
such holder and such holder shall sell to Tetra Tech on the Retraction Date the
Retracted Shares for the Retraction Call Purchase Price. For the purposes of
completing a purchase pursuant to a Retraction Call Right, Tetra Tech shall
deposit with the Corporation, on or before the Retraction Date, certificates
representing the number of shares of Tetra Tech Common Shares to which such
holder is entitled and a cheque in the amount of the remaining portion, if any,
of the aggregate Retraction Call Purchase Price to which such holder is
entitled. Provided that the aggregate Retraction Call Purchase Price has been so
deposited with the Corporation, the closing of the purchase and sale of the
Retracted Shares pursuant to the Retraction Call Right shall be deemed to have
occurred as at the close of business on the Retraction Date and, for greater
certainty, no redemption by the Corporation of such Retracted Shares shall take
place on the Retraction Date. In the event that Tetra Tech shall not deliver a
Tetra Tech Call Notice within such two Business Day period, and provided that
the Retraction Request is not revoked by the holder in the manner specified in
Section 4.1(5), the Corporation shall redeem the Retracted Shares on the
Retraction Date and in the manner otherwise contemplated in Section 4.1.
<PAGE>
<PAGE>
     (c)  For the purpose of completing a purchase of Exchangeable Shares
pursuant to the exercise of a Retraction Call Right, Tetra Tech shall deliver or
cause the Corporation to deliver to the relevant holder, at the address of the
holder recorded in the securities register of the Corporation for the
Exchangeable Shares or at the address specified in the holder's Retraction
Request or by holding for pick-up by the holder at the registered office of the
Corporation, a certificate representing the number of Tetra Tech Common Shares
to which such holder is entitled (which shares shall be duly issued as fully
paid and non-assessable and shall be free and clear of any lien, claim,
encumbrance, security interest or adverse claim) registered in the name of the
holder or in such other name as the holder may request in payment of the
Retraction Call Purchase Price and a cheque of Tetra Tech payable at par at any
branch of the bankers of Tetra Tech or of the Corporation in Canada in payment
of the remaining portion, if any, of such aggregate Retraction Call Purchase
Price and such delivery of such certificate and cheque on behalf of Tetra Tech
by the Corporation shall be deemed to be payment of and shall satisfy and
discharge all liability for the Retraction Call Purchase Price to the extent
that the same is represented by such share certificates and cheque, unless such
cheque is not paid on due presentation.  The Corporation shall, for the purposes
of endorsing the certificates evidencing the Exchangeable Shares, act as the
attorney in fact for all holders of Exchangeable Shares.

     (d)  On and after the close of business on the Retraction Date, the holder
of the Retracted Shares shall not be entitled to exercise any of the rights of a
holder in respect thereof, other than the right to receive the Retraction Call
Purchase Price unless upon presentation and surrender of certificates in
accordance with the foregoing provisions, payment of the Retraction Call
Purchase Price shall not be made, in which case the rights of such holder shall
remain unaffected until the Retraction Call Purchase Price has been paid in the
manner hereinbefore provided. On and after the close of business on the
Retraction Date, provided that presentation and surrender of certificates and
payment of the Retraction Call Purchase Price has been made in accordance with
the foregoing provisions, the holder of the Retracted Shares so purchased by
Tetra Tech shall thereafter be considered and deemed for all purposes to be a
holder of the Tetra Tech Common Shares delivered to such holder.

     (e)  At any time after the exercise of any Retraction Call Right, the
Exchangeable Shares then held by Tetra Tech may be redeemed by the Corporation
upon payment by the Corporation to Tetra Tech of a redemption price equivalent
to $.0001 per Exchangeable Share.


                                   ARTICLE 5
                                EXCHANGE RIGHT

5.1  GRANT AND OWNERSHIP OF THE EXCHANGE RIGHT

     All holders of Exchangeable Shares (defined in this Article 5 as the
"Shareholders") shall have the right (the "Exchange Right") at any time after
five months from the date of issue of the Exchangeable Shares, to require Tetra
Tech to purchase all or any part of the Exchangeable Shares held by the
Shareholder, all in accordance with the provisions of the Support Agreement.
<PAGE>
<PAGE>
5.2  PURCHASE PRICE

     The purchase price payable by Tetra Tech for each Exchangeable Share to be
purchased by Tetra Tech under the Exchange Right shall be an amount per share
equal to (a) the Current Market Price of a Tetra Tech Common Share on the last
Business Day prior to the day of closing of the purchase and sale of such
Exchangeable Share under the Exchange Right (the "Exchange Date"), which shall
be satisfied in full by causing to be delivered to such holder one Tetra Tech
Common Share, plus (b) the Dividend Amount, if any. The purchase price for each
such Exchangeable Share so purchased shall be satisfied only by Tetra Tech
delivering or causing to be delivered to the Shareholder, one Tetra Tech Common
Share and a cheque payable at par at any branch of the bankers of Tetra Tech or
of the Corporation in Canada in payment of the balance, if any, of the purchase
price.

5.3  EXERCISE INSTRUCTIONS

     Subject to the terms and conditions hereof, to exercise the Exchange Right,
a Shareholder shall deliver in person or by certified or registered mail, at the
principal office of the Corporation, the certificates representing the
Exchangeable Shares which such Shareholder desires Tetra Tech to purchase, duly
endorsed in blank, and accompanied by such other documents and instruments as
may be required to effect a transfer of Exchangeable Shares under the OBCA and
such additional documents and instruments as the Corporation may reasonably
require together with a duly completed form of notice of exercise of the
Exchange Right, contained on the reverse of or attached to the Exchangeable
Share certificates, stating (i) that the Shareholder thereby exercises the
Exchange Right so as to require Tetra Tech to purchase from the Shareholder the
number of Exchangeable Shares specified therein, (ii) that such Shareholder has
good title to and owns all such Exchangeable Shares to be acquired by Tetra Tech
free and clear of all liens, claims and encumbrances, (iii) the names in which
the certificates representing Tetra Tech Common Shares issuable in connection
with the exercise of the Exchange Right are to be issued and (iv) the names and
addresses of the persons to whom such new certificates should be delivered.

5.4  DELIVERY OF TETRA TECH COMMON SHARES; EFFECT OF EXERCISE

     Promptly after receipt of the certificates representing the Exchangeable
Shares that a Shareholder desires Tetra Tech to purchase under the Exchange
Right duly endorsed for transfer to Tetra Tech, the Corporation shall notify
Tetra Tech of its receipt of the same, which notice to Tetra Tech shall
constitute exercise of the Exchange Right by the Shareholder, and Tetra Tech
shall immediately thereafter deliver to the relevant Shareholder of such
Exchangeable Shares, a certificate for the number of Tetra Tech Common Shares
deliverable in connection with such exercise of the Exchange Right (which shares
shall be duly issued as fully paid and non-assessable and shall be free and
clear of any lien, claim or encumbrance, security interest or adverse claim) and
a cheque for the balance, if any, of the purchase price therefor; provided,
however, that no such delivery shall be made unless and until the Shareholder
requesting the same shall have paid any applicable taxes.
<PAGE>
<PAGE>
Immediately upon the giving of notice by the Shareholder to Tetra Tech and the
Corporation of the exercise of the Exchange Right, as provided in this section
5.4, the closing of the transaction of purchase and sale contemplated by the
Exchange Right shall be deemed to have occurred, and the Shareholder of such
Exchangeable Shares shall be deemed to have transferred to Tetra Tech all of its
right, title and interest in and to such Exchangeable Shares and shall not be
entitled to exercise any of the rights of a holder in respect thereof, other
than the right to receive the purchase price therefor, unless the requisite
number of Tetra Tech Common Shares (together with a cheque for the balance, if
any, of such purchase price) is not delivered by Tetra Tech to the Shareholder
within five Business Days of the date of the giving of such notice by the
Shareholder, in which case the rights of the Shareholder shall remain unaffected
until such Tetra Tech Common Shares are so delivered and any such cheque is so
delivered and paid.  Concurrently with the closing of the transaction of
purchase and sale contemplated by the Exchange Right, such Shareholder shall be
considered and deemed for all purposes to be the holder of the Tetra Tech Common
Shares delivered to it pursuant to the Exchange Right.


                                   ARTICLE 6
                     RECIPROCAL CHANGES, ETC. IN RESPECT OF
                            TETRA TECH COMMON SHARES

6.1  The Exchangeable Share Provisions shall be adjusted to fully reflect the
effect of any stock split, reverse split, reorganization, recapitalization or
other like change with respect to the Tetra Tech Common Shares; provided,
however, that no such adjustment shall require a fractional Tetra Tech Common
Share to be delivered to a holder of Exchange Shares on any retraction or
exchange thereof.  In lieu thereof, each holder of Exchangeable Shares who wold
otherwise be entitled to a fraction of a Tetra Tech Common Share will be
entitled to receive a cheque for an amount (rounded to the nearest cent) equal
to the product of (i) such fraction and (ii) the Current Market Price of a Tetra
Tech Common Share on the last Business Day prior to the Retraction Date or the
Exchange Date, as applicable.


                                   ARTICLE 7
                                 VOTING RIGHTS

7.1  Except as required by applicable law and the provisions hereof, the holders
of the Exchangeable Shares shall not be entitled as such to receive notice of or
to attend any meeting of the shareholders of the Corporation or to vote at any
such meeting.  Without limiting the generality of the foregoing, the holders of
the Exchangeable Shares shall not be entitled to vote separately as a class on
any proposal to amend the articles to:

     (a)  increase any maximum number of authorized shares of a class having
rights equal to or superior
               to the Exchangeable Shares; or

     (b)  create a new class of shares equal to or superior to the Exchangeable
Shares.
<PAGE>
<PAGE>
The holders of the Exchangeable Shares shall, however, be entitled to notice of
meetings of the shareholders called for the purpose of authorizing the
dissolution of the Corporation or the sale, lease or exchange of all or
substantially all the property of the Corporation other than in the ordinary
course of business of the Corporation.


                                   ARTICLE 8
                             AMENDMENT AND APPROVAL

8.1  The rights, privileges, restrictions and conditions attaching to the
Exchangeable Shares may be added to, changed or removed only with the approval
of the holders of the Exchangeable Shares given as hereinafter specified.

8.2  Any approval given by the holders of the Exchangeable Shares to add to,
change or remove any right, privilege, restriction or condition attaching to the
Exchangeable Shares or any other matter requiring the approval or consent of the
holders of the Exchangeable Shares shall be deemed to have been sufficiently
given if it shall have been given in accordance with applicable law subject to a
minimum requirement that such approval be evidenced by resolution passed by not
less than two-thirds of the votes cast on such resolution at a meeting of
holders of Exchangeable Shares duly called and held at which the holders of at
least 50% of the outstanding Exchangeable Shares at that time are present or
represented by proxy.  If at any such meeting the holders of at least 50% of the
outstanding Exchangeable Shares at that time are not present or represented by
proxy within one-half hour after the time appointed for such meeting then the
meeting shall be adjourned to such date not less than 10 days thereafter and to
such time and place as may be designated by the chairman of such meeting.  At
such adjourned meeting the holders of Exchangeable Shares present or represented
by proxy thereat may transact the business for which the meeting was originally
called and a resolution passed thereat by the affirmative vote of not less than
two-thirds of the votes cast on such resolution at such meeting shall constitute
the approval or consent of the holders of the Exchangeable Shares.


                                   ARTICLE 9
                           ACTIONS BY THE CORPORATION
                          UNDER THE SUPPORT AGREEMENT

9.1  The Corporation shall take all such actions and do all such things as shall
be necessary or advisable to perform and comply with and to ensure performance
and compliance by Tetra Tech with all provisions of the Support Agreement
applicable to the Corporation and Tetra Tech, respectively, in accordance with
the terms thereof including, without limitation, taking all such actions and
doing all such things as shall be necessary or advisable to enforce to the
fullest extent possible for the direct benefit of the Corporation and the
holders of the Exchangeable Shares all rights and benefits in favour of the
Corporation and the holders of the Exchangeable Shares under or pursuant to such
agreement.  The Corporation shall take all such action and do all such things as
aforesaid upon the reasonable direction of a holder of Exchangeable Shares, at
such holder's cost and expense and upon the Corporation being indemnified to its
reasonable satisfaction against all such costs and expenses and any liabilities
that may be incurred.
<PAGE>
<PAGE>
9.2  The Corporation shall not agree to or otherwise give effect to any
amendment to, or waiver or forgiveness of its rights or obligations under the
Support Agreement without the approval of the holders of the Exchangeable Shares
other than such amendments, waivers and/or forgiveness as may be necessary or
advisable for the purposes of:

     a)   adding to the covenants of the other party or parties to such
agreement for the protection of the Corporation or the holders of Exchangeable
Shares;

     b)   making such provisions or modifications not inconsistent with such
agreement as may be necessary or desirable with respect to matters or questions
arising thereunder which, in the opinion of the Board of Directors, it may be
expedient to make, provided that the Board of Directors shall be of the opinion,
after consultation with counsel, that such provisions and modifications will not
be prejudicial to the interests    of the holders of the Exchangeable Shares; or

     c)   making such changes in or corrections to such agreement which, on the
advice of counsel to the Corporation, are required for the purpose of curing or
correcting any ambiguity or defect or inconsistent provision or clerical
omission or mistake or manifest error contained therein, provided that the Board
of Directors shall be of the opinion, after consultation with counsel, that such
changes or corrections will not be prejudicial to the interests of the holders
of the Exchangeable Shares.


                                   ARTICLE 10
                                     LEGEND

10.1 The certificates evidencing the Exchangeable Shares shall contain or have
affixed thereto a legend, in form and on terms approved by the Board of
Directors, with respect to the provisions of the Support Agreement (including
the provisions with respect to the call rights and exchange rights thereunder).
<PAGE>
<PAGE>
                                                               EXHIBIT 1.2B
                               SUPPORT AGREEMENT


                    AGREEMENT made as of September 22, 1998

                                    BETWEEN:


               TETRA TECH, INC., a corporation existing under the
               laws of the State of Delaware (the "Parent"),

                                    - and -

               TETRA TECH CANADA LTD., a corporation existing under
               the laws of the Province of Ontario (the "Corporation"),


     WHEREAS the Corporation has agreed to acquire all of the issued and
outstanding shares of Cen-Comm Communications Inc., 1056585 Ontario Limited,
1056584 Ontario Limited, Venture Cable Ltd., Sentrex Electronics Limited and LAL
Corp. (collectively the "Sentrex Companies") and the shareholders of the Sentrex
Companies will receive Exchangeable Shares (as hereinafter defined) of the
Corporation as consideration for the sale of such shares;

     AND WHEREAS pursuant to the Exchangeable Share Provisions (as hereinafter
defined), the Parent has certain rights and obligations in respect of Parent
Common Stock (as hereinafter defined);

     AND WHEREAS the Parent intends to grant to and in favour of Holders (as
hereinafter defined) from time to time of Exchangeable Shares the right, in the
circumstances set forth herein, to require the Parent to purchase from each
Holder all or any part of the Exchangeable Shares held by the Holder;

     NOW THEREFORE, in consideration of the respective covenants and agreements
provided in this Agreement and for other good and valuable consideration (the
receipt and sufficiency of which are hereby acknowledged), the parties agree as
follows:

<PAGE>
<PAGE>
                                   ARTICLE 1

                         DEFINITIONS AND INTERPRETATION

1.1  DEFINITIONS.  In this Agreement, unless something in the subject matter or
content is inconsistent therewith:

     "BOARD OF DIRECTORS" means the board of directors of the Corporation.

     "BUSINESS DAY" means a day other than a Saturday, a Sunday or a day when
banks are not open for business in Ottawa, Ontario.

     "CANADIAN DOLLAR EQUIVALENT" means in respect of an amount expressed in a
foreign currency (the "Foreign Currency Amount") at any date the product
obtained by multiplying (a) the Foreign Currency Amount by (b) the official noon
spot exchange rate on such date for such foreign currency as reported by the
Bank of Canada or, in the event such spot exchange rate is not available, such
exchange rate on such date for such foreign currency as may be deemed by the
Board of Directors to be appropriate for such purpose.

     "CURRENT MARKET PRICE" means, in respect of a share of Parent Common Stock
on any date, the Canadian Dollar Equivalent of the fair market value of a share
of Parent Common Stock as determined by averaging the closing trading price for
the Parent Common Stock for the 5 day period preceding the particular date on
the Exchange on which the Parent Common Stock principally trades.

     "DIVIDEND AMOUNT" has the meaning set out in Section 1.1 of the
Exchangeable Share Provisions.

     "EXCHANGE DATE" has the meaning set out in Section 5.2 of the Exchangeable
Share Provisions

     "EXCHANGE RIGHT" has the meaning set out in Section 5.1 of the Exchangeable
Share Provisions and Section 2.1 hereof.

     "EXCHANGEABLE SHARE PROVISIONS" means the rights, privileges, restrictions
and conditions attaching to the Exchangeable Shares, a copy of which are
attached hereto as Schedule A.

     "EXCHANGEABLE SHARES" means the special shares which are known as
exchangeable shares to be issued by the Corporation to holders of shares of the
Sentrex Companies.

     "HOLDERS" means the registered holders of Exchangeable Shares.

     "PARENT COMMON STOCK" means shares of common stock, par value $.01, of the
Parent and any other securities into which such shares may be changed or for
which such shares may be exchanged (whether or not the Parent shall be the
issuer of such other securities) or any other consideration which may be
received by the holders of such shares, pursuant to a recapitalization,
reconstruction, reorganization or reclassification of, or amalgamation, merger,
liquidation or similar transaction, affecting such shares.
<PAGE>
<PAGE>
     "RETRACTED SHARES has the meaning set out in Section 2.6 hereof.

     "RETRACTION CALL RIGHT" has the meaning set out in Section 4.2(a) of the
Exchangeable Share Provisions.

     "RETRACTION DATE" has the meaning set out in Section 4.1(a) of the
Exchangeable Share Provisions.

     "RETRACTION PRICE" has the meaning set out in Section 4.1(a) of the
Exchangeable Share Provisions.

1.2  INTERPRETATION NOT AFFECTED BY HEADINGS, ETC.  The division of this
Agreement into articles and sections and the insertion of headings are for
reference purposes only and shall not affect the interpretation of this
Agreement.  Unless otherwise indicated, any reference in this Agreement to an
article or section refers to the specified article or section of this Agreement.

1.3  NUMBER GENDER AND PERSONS.  In this Agreement, unless the context otherwise
requires, words importing the singular number include the plural and vice versa,
words importing any gender include all genders and words importing persons
include individuals, corporations, partnerships, companies, associations,
trusts, unincorporated organizations, governmental bodies and other legal or
business entities of any kind.

1.4  DATE FOR ANY ACTION.  If any date on which any action is required to be
taken under this Agreement is not a Business Day, such action shall be required
to be taken on the next succeeding Business Day.

1.5  PAYMENTS.  All payments to be made hereunder will be made without interest
and less any tax required by law to be deducted and withheld.


                                   ARTICLE 2

                       EXCHANGE RIGHT AND PARENT SUPPORT

2.1  GRANT AND OWNERSHIP OF THE EXCHANGE RIGHT.  The Parent hereby grants to the
Holders the right (the "Exchange Right") to require the Parent to purchase from
each or any Holder all or any part of the Exchangeable Shares held by the
Holder, all in accordance with the provisions of this Agreement.  The Parent
hereby acknowledges receipt from the Corporation and on behalf of the Holders,
of good and valuable consideration (and the adequacy thereof) for the grant of
the Exchange Right by the Parent to the Holders.

2.2  LEGENDED SHARE CERTIFICATES.  The Corporation will cause each certificate
representing Exchangeable Shares to bear an appropriate legend notifying the
Holders of their right to instruct the Corporation with respect to the exercise
of the Exchange Right in respect of the Exchangeable Shares held by a Holder.
<PAGE>
<PAGE>
2.3  PURCHASE PRICE.  The purchase price payable by the Parent for each
Exchangeable Share to be purchased by the Parent under the Exchange Right shall
be an amount per share equal to (a) the Current Market Price of a share of
Parent Common Stock on the last Business Day prior to the Exchange Date, which
shall be satisfied in full by causing to be delivered to such Holder one share
of Parent Common Stock, plus (b) the Dividend Amount, if any. The purchase price
for each such Exchangeable Share so purchased shall be satisfied only by the
Parent delivering or causing to be delivered to the Holder or the Corporation,
on behalf of the relevant  Holder, one share of Parent Common Stock and a cheque
payable at par at any branch of the bankers of the Parent or of the Corporation
in Canada in payment of the balance, if any, of the purchase price.

2.4  EXERCISE INSTRUCTIONS.  Subject to the terms and conditions herein set
forth, a Holder shall be entitled to exercise the Exchange Right with respect to
any number of the Exchangeable Shares registered in the name of such Holder on
the books of the Corporation at any time after the fifth month from the date of
issue of the Exchangeable Shares.  To exercise of the Exchange Right, the Holder
shall deliver in person or by certified or registered mail, at the principal
office of the Corporation, the certificates representing the Exchangeable Shares
which such Holder desires the Parent to purchase, duly endorsed in blank, and
accompanied by such other documents and instruments as may be required to effect
a transfer of Exchangeable Shares under the Business Corporations Act (Ontario)
and such additional documents and instruments as the Corporation may reasonably
require together with a duly completed form of notice of exercise of the
Exchange Right, contained on the reverse of or attached to the Exchangeable
Share certificates, stating (i) that the Holder thereby exercises the Exchange
Right so as to require the Parent to purchase from the Holder the number of
Exchangeable Shares specified therein, (ii) that such Holder has good title to
and owns all such Exchangeable Shares to be acquired by the Parent free and
clear of all liens, claims and encumbrances, (iii) the names in which the
certificates representing Parent Common Stock issuable in connection with the
exercise of the Exchange Right are to be issued and (iv) the names and addresses
of the persons to whom such new certificates should be delivered.

2.5  DELIVERY OF PARENT COMMON STOCK; EFFECT OF EXERCISE.  Promptly after
receipt of the certificates representing the Exchangeable Shares that a Holder
desires the Parent to purchase under the Exchange Right duly endorsed for
transfer to the Parent, the Corporation shall notify the Parent of its receipt
of the same, which notice to the Parent shall constitute exercise of the
Exchange Right by the Holder of such Exchangeable Shares, and the Parent shall
immediately thereafter deliver to the Corporation, on behalf of the relevant
Holder of such Exchangeable Shares, a certificate for the number of shares of
Parent Common Stock deliverable in connection with such exercise of the Exchange
Right (which shares shall be duly issued as fully paid and non-assessable and
shall be free and clear of any lien, claim or encumbrance, security interest or
adverse claim) and a cheque for the balance, if any, of the purchase price
therefor; provided, however, that no such delivery shall be made unless and
until the Holder requesting the same shall have paid any applicable taxes.
<PAGE>
<PAGE>
Immediately upon the giving of notice by the Corporation to the Parent of the
exercise of the Exchange Right, as provided in this Section 2.5, the closing of
the transaction of purchase and sale contemplated by the Exchange Right shall be
deemed to have occurred, and the Holder of such Exchangeable Shares shall be
deemed to have transferred to the Parent all of its right, title and interest in
and to such Exchangeable Shares and shall not be entitled to exercise any of the
rights of a Holder in respect thereof, other than the right to receive the
purchase price therefor, unless the requisite number of shares of Parent Common
Stock (together with a cheque for the balance, if any, of the total purchase
price therefor) is not delivered by the Parent to the Holder or to the
Corporation on behalf of the Holder within five Business Days of the date of the
giving of such notice by the Holder, in which case the rights of the Holder
shall remain unaffected until such shares of Parent Common Stock are so
delivered and any such cheque is so delivered and paid.  Concurrently with the
closing of the transaction of purchase and sale contemplated by the Exchange
Right, such Holder shall be considered and deemed for all purposes to be the
holder of the shares of Parent Common Stock delivered to it pursuant to the
Exchange Right.

2.6  EXERCISE OF EXCHANGE RIGHT SUBSEQUENT TO RETRACTION.  In the event that a
Holder has exercised its right under Article 4 of the Exchangeable Share
Provisions to require the Corporation to redeem any or all of the Exchangeable
Shares held by the Holder (the "Retracted Shares"), the Parent shall be entitled
to exercise the Retraction Call Right in respect of such shares.  If the Parent
has not exercised the Retraction Call Right in respect of the Retracted Shares
and such Holder is notified by the Corporation pursuant to Section 4.1(d) of the
Exchangeable Share Provisions that the Corporation will not be permitted as a
result of solvency requirements or other provisions of applicable law to redeem
all such Retracted Shares, provided that the Holder shall not have revoked the
retraction request delivered by the Holder to the Corporation pursuant to
Section 4.1(e) of the Exchangeable Share Provisions, the retraction request will
constitute and will be deemed to constitute notice from the Holder of its
exercise of the Exchange Right with respect to those Retracted Shares that the
Corporation is unable to redeem.  In any such event, the Corporation hereby
agrees in favour of the Holder immediately to notify the Holder of such
prohibition against the Corporation redeeming all of the Retracted Shares and
immediately to forward or cause to be forwarded to the Parent all relevant
materials delivered by the Holder to the Corporation in connection with such
proposed redemption of the Retracted Shares and the Holders will thereupon
exercise the Exchange Right with respect to the Retracted Shares that the
Corporation is not permitted to redeem and will require the Parent to purchase
such shares in accordance with the provisions of this Article 2.

<PAGE>
<PAGE>
                                   ARTICLE 3

                   COVENANTS, REPRESENTATIONS AND WARRANTIES

3.1  CERTAIN REPRESENTATIONS.  The Parent hereby represents, warrants and
covenants that it has irrevocably reserved for issuance and will at all times
keep available, free from preemptive and other rights, out of its authorized and
unissued capital stock such number of shares of Parent Common Stock (or other
shares or securities into which the Parent Common Stock may be reclassified or
changed) (a) as is equal to the sum of (i) the number of Exchangeable Shares
issued and outstanding from time to time and (ii) the number of Exchangeable
Shares issuable upon the exercise of all rights to acquire Exchangeable Shares
outstanding from time to time and (b) as is now and may hereafter be required to
enable and permit each of the Corporation and the Parent to meet its obligations
hereunder and under the Exchangeable Share Provisions.

3.2  DELIVERY OF SHARES OF PARENT COMMON STOCK.  Upon notice of any event that
requires the Corporation to cause to be delivered shares of Parent Common Stock
to any holder of Exchangeable Shares, the Parent shall, in any manner deemed
appropriate by it, provide such shares or cause such shares to be provided to
the Corporation, which shall forthwith deliver the requisite shares of Parent
Common Stock to or to the order of the former holder of the surrendered
Exchangeable Shares, as the Corporation shall direct.  All such shares of Parent
Common Stock shall be duly issued as fully paid, non-assessable, free of pre-
emptive rights and shall be free and clear of any lien, claim, encumbrance,
security interest or adverse claim.

3.3  QUALIFICATION OF SHARES OF PARENT COMMON STOCK.  The Parent covenants that
if any shares of Parent Common Stock (or other shares or securities into which
the Parent Common Stock may be reclassified or changed) to be issued and
delivered hereunder, require registration or qualification with or approval of
or the filing of any document including any prospectus or similar document or
the taking of any proceeding with or the obtaining of any order, ruling or
consent from any governmental or regulatory authority under any Canadian or
United States federal, provincial or state law or regulation or pursuant to the
rules and regulations of any regulatory authority or the fulfilment of any other
legal requirement (collectively, the "Applicable Laws") before such shares may
be issued and delivered by the Parent to the initial holder thereof, the Parent
will in good faith expeditiously take all such actions and do all such things as
are necessary to cause such shares of Parent Common Stock to be and remain duly
registered, qualified or approved.

3.4  RECIPROCAL CHANGES, ETC. IN RESPECT OF PARENT COMMON STOCK.  The
Exchangeable Share Provisions and the provisions of this Agreement shall be
adjusted to fully reflect the effect of any stock split, reverse split,
reorganization, recapitalization or other like change with respect to the shares
of Parent Common Stock; provided, however, that no such adjustment shall require
a fractional share of Parent Common Stock to be delivered to a holder of
Exchange Shares on any retraction or exchange thereof.
<PAGE>
<PAGE>
In lieu thereof, each holder of Exchangeable Shares who wold otherwise be
entitled to a fraction of a share of Parent Common Stock will be entitled to
receive a cheque for an amount (rounded to the nearest cent) equal to the
product of (i) such fraction and (ii) the Current Market Price of a share of
Parent Common Stock on the last Business Day prior to the Retraction Date or the
Exchange Date, as applicable

3.5  ENFORCEMENT OF RIGHTS.  The Parent acknowledges that in the event it fails
to perform any obligation hereunder in favour of the Holder, the Corporation
may, and shall at the reasonable direction of a Holder, enforce any such
obligation of the Holder on behalf of such Holder.

3.6  CONSENT TO TRANSFER OF EXCHANGEABLE SHARES.  The Parent, as the sole holder
of common shares of the Corporation, hereby irrevocably consents to any and all
transfers of Exchangeable Shares made in compliance with the Exchangeable Share
Provisions and this Agreement.


                                   ARTICLE 4

                               PARENT SUCCESSORS

4.1  CERTAIN REQUIREMENTS IN RESPECT OF COMBINATION, ETC.  The Parent shall not
enter into any transaction (whether by way of reconstruction, reorganization,
consolidation, merger, transfer, sale, lease or otherwise) whereby all or
substantially all of its undertaking, property and assets would become the
property of any other person or, in the case of a merger, of the continuing
corporation resulting therefrom unless, but may do so if:

     (a)  such other person or continuing corporation (the "Parent Successor"),
          by operation of law, becomes, without more, bound by the terms and
          provisions of this Agreement or, if not so bound, executes, prior
          to or contemporaneously with the consummation of such transaction an
          agreement supplemental hereto and such other instruments (if any) as
          are satisfactory to the Corporation and in the opinion of legal
          counsel to the Corporation are necessary or advisable to evidence the
          assumption by the Parent Successor of liability for all money payable
          and property deliverable hereunder and the covenant of such Parent
          Successor to pay and deliver or cause to be delivered the same and its
          agreement to observe and perform all the covenants and obligations of
          the Parent under this Agreement; and

     (b)  such transaction shall, to the satisfaction of the Corporation and in
          the opinion of legal counsel to the Corporation, be upon such terms as
          substantially to preserve and not to impair in any material respect
          any of the rights, duties, powers and authorities of the Corporation
          or of the Holders hereunder.
<PAGE>
<PAGE>
4.2  VESTING OF POWERS IN SUCCESSOR.  Whenever the conditions of Section 4.1
hereof have been duly observed and performed, if required by Section 4.1 hereof,
the Corporation and the Parent Successor shall execute and deliver the
supplemental agreement provided and thereupon the Parent Successor shall possess
and from time to time may exercise each and every right and power of the Parent
under this Agreement in the name of the Parent or otherwise and any act or
proceeding by any provision of this Agreement required to be done or performed
by the board of directors of the Parent or any officers of the Parent may be
done and performed with like force and effect by the directors or officers of
such Parent Successor.


                                   ARTICLE 5

                                   AMENDMENTS

5.1  AMENDMENTS, MODIFICATIONS, ETC.  This Agreement may not be amended or
modified except by an agreement in writing executed by the Corporation and the
Parent and approved by the Holders in accordance with Section 8.2 of the
Exchangeable Share Provisions.

5.2  MINISTERIAL AMENDMENTS.  Notwithstanding the provisions of Section 5.1
hereof, the parties to this Agreement may in writing, at any time and from time
to time, without the approval of the Holders, amend or modify this Agreement for
the purposes of:

     (a)  adding to the covenants of any or all of the parties hereto for the
          protection of the Holders hereunder;

     (b)  making such amendments or modifications not inconsistent with this
          Agreement as may be necessary or desirable with respect to matters or
          questions which, in the opinion of the Board of Directors and the
          board of directors of the Parent  having in mind the best interests of
          the Holders as a whole, it may be expedient to make, provided that
          such boards of directors shall be of the opinion that such amendments
          and modifications will not be prejudicial to the interests of the
          Holders as a whole; or

     (c)  making such changes or corrections which, on the advice of counsel to
          the Corporation and the Parent, are required for the purpose of curing
          or correcting any ambiguity or defect or inconsistent provision or
          clerical omission or mistake or manifest error, provided that the
          Corporation and its counsel and the Board of Directors and the board
          of directors of the Parent shall be of the opinion that such changes
          or corrections will not be prejudicial to the interests of the Holders
          as a whole.

Any other amendments hereto require the approval of Holders in accordance with
Section 8.2 of the Exchangeable Share Provisions.
<PAGE>
<PAGE>
5.3  MEETING TO CONSIDER AMENDMENTS.  The Corporation, at the request of the
Parent, shall call a meeting or meetings of the Holders for the purpose of
considering any proposed amendment or modification requiring approval pursuant
hereto. Any such meeting or meetings shall be called and held in accordance with
the by-laws of the Corporation, the Exchangeable Share Provisions and all
applicable laws.

5.4  CHANGES IN CAPITAL OF PARENT AND THE CORPORATION.  At all times after the
occurrence of any event effected pursuant to Section 3.4 or 4.1 of this
Agreement, as a result of which either the Parent Common Stock or the
Exchangeable Shares or both are in any way changed, this Agreement shall
forthwith be amended and modified as necessary in order that it shall apply with
full force and effect, MUTATIS MUTANDIS, to all new securities into which the
Parent Common Stock or the Exchangeable Shares or both are so changed and the
parties hereto shall execute and deliver an agreement giving effect to and
evidencing such necessary amendments and modifications.


                                   ARTICLE 6

                                  TERMINATION

6.1  SURVIVAL OF AGREEMENT.  This Agreement shall terminate at such time as
there are no Exchangeable Shares outstanding held by any Holder other than the
Parent.


                                   ARTICLE 7

                                    GENERAL

7.1  SEVERABILITY.  If any provision of this Agreement is held to be invalid,
illegal or unenforceable, the validity, legality or enforceability of the
remainder of this Agreement shall not in any way be affected or impaired thereby
and this Agreement shall be carried out as nearly as possible in accordance with
its original terms and conditions.

7.2  ENUREMENT.  This Agreement shall be binding upon and enure to the benefit
of the parties hereto and their respective successors and permitted assigns and
to the benefit of the Holders.

7.3  COUNTERPARTS.  This Agreement may be executed in counterparts, each of
which shall be deemed an original, but all of which taken together shall
constitute one and the same instrument.

7.4  JURISDICTION.  This Agreement shall be construed and enforced in accordance
with the laws of the Province of Ontario and the laws of Canada applicable
therein.
<PAGE>
<PAGE>
7.5  ATTORNMENT.  The Parent agrees that any action or proceeding arising out of
or relating to this Agreement may be instituted in the courts of Ontario, waives
any objection which it may have now or hereafter to the venue of any such action
or proceeding, irrevocably submits to the jurisdiction of the said courts in any
such action or proceeding, agrees to be bound by any judgment of the said courts
and agrees not to seek, and hereby waives, any review of the merits of any such
judgment by the courts of any other jurisdiction and hereby appoints the
Corporation at its registered office in the Province of Ontario as its attorney
for service of process.

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the date first above written.


                                        TETRA TECH, INC.

                                        By:    ______________________________
                                        Name:
                                        Title:


                                        TETRA TECH CANADA LTD.

                                        By:    ______________________________
                                        Name:
                                        Title:

<PAGE>
<PAGE>
                                                                            
EXHIBIT 1.2C
<TABLE>
<CAPTION>
                                    STOCK PURCHASE AGREEMENT AMONG TETRA TECH, INC. AND
                                              THE SENTREX GROUP OF COMPANIES

Consideration to be Received by the Company's Shareholders

                                           Relative        Total         Desired Share     Shares @       Share           Cash
    Shareholder               Shares      Ownership    Consideration         Value*         19.70         Value          Value 
  ---------------           ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  <C>                       <S>          <S>           <S>              <S>               <S>         <S>             <S>
  1056584 ONTARIO LIMITED
  Leonard Stanmore               101        100.00%        3,064,789         2,451,831     124,458     2,451,822.60     612,966.40
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                          101        100.00%        3,064,789         2,451,831     124,458     2,451,822.60     612,966.40
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  1056585 ONTARIO LIMITED
  Peter Nicoletti                101        100.00%        2,417,714         1,934,171      98,181     1,934,165.70     483,548.30
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                          101        100.00%        2,417,714         1,934,171      98,181     1,934,165.70     483,548.30
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  VENTURE CABLE LIMITED
  Leonard Stanmore                32         32.00%           68,265            54,612       2,772        54,608.40      13,656.60
  Peter Nicoletti                 32         32.00%           68,265            54,612       2,772        54,608.40      13,656.60
  Andre Greco                     18         18.00%           69,615            69,615       3,533        69,600.10          14.90
  Gordon Brooks                   18         18.00%           69,615            55,692       2,827        55,691.90      13,923.10
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                          100        100.00%          275,760           234,531      11,904       234,508.80      41,251.20
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  CEN-COMM COMMUNICATION, INC.
  Raymond Conroy                 124         40.00%        1,223,635           978,908      49,690       978,893.00     244,742.00
  Elizabeth Stanmore             186         60.00%        1,844,046         1,475,237      74,885     1,475,234.50     368,811.50
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                          310        100.00%        3,067,681         2,454,145     124,575     2,454,127.50     613,553.50 
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  SENTREX ELECTRONICS INC.
  Leonard Stanmore               100         16.67%          116,060            92,848       4,713        92,846.10      23,213.90
  Peter Nicoletti                100         16.67%          116,060            92,848       4,713        92,846.10      23,213.90
  James Suen                     200         33.33%          219,257           175,406       8,903       175,389.10      43,867.90
  Elizabeth Stanmore             100         16.67%          116,060            92,848       4,713        92,846.10      23,213.90
  Silvana Nicoletti              100         16.67%          116,060            92,848       4,713        92,846.10      23,213.90
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                          600        100.00%          683,497           546,798      27,755       546,773.50     136,723.50
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  LAL CORP.
  Leonard Stanmore             1,350         45.00%        5,911,650         4,729,320     240,067     4,729,319.90   1,182,330.10
  Peter Nicoletti                750         25.00%        3,284,250         2,627,400     133,370     2,627,389.00     656,861.00
  James Suen                     300         10.00%        1,313,700         1,050,960      53,348     1,050,955.60     262,744.40
  Raymond Conroy                 600         20.00%        2,627,400         2,101,920     106,696     2,101,911.20     525,488.80
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                        3,000        100.00%       13,137,000        10,509,600     533,481    10,509,575.70   2,627,424.30
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
<PAGE>
<PAGE>

  GRAND TOTALS
  Leonard Stanmore             1,583         37.58%        9,160,764         7,328,611     372,010     7,328,597.00   1,832,167.00
  Peter Nicoletti                983         23.34%        5,886,289         4,709,031     239,036     4,709,009.20   1,177,279.80
  Raymond Conroy                 724         17.19%        3,851,035         3,080,828     156,386     3,080,804.20     770,230.80
  James Suen                     500         11.87%        1,532,957         1,226,366      62,251     1,226,344.70     306,612.30
  Elizabeth Stanmore             286          6.79%        1,960,106         1,568,085      79,598     1,568,080.60     392,025.40
  Silvana Nicoletti              100          2.37%          116,060            92,848       4,713        92,846.10      23,213.90
  Andre Greco                     18          0.43%           69,615            69,615       3,533        69,600.10          14.90
  Gordon Brooks                   18          0.43%           69,615            55,692       2,827        55,691.90      13,923.10
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
  Total                        4,212        100.00%       22,646,411        18,131,076     920,354    18,130,973.80   4,515,467.20
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------
                            ----------   ------------  ---------------  ---------------   ----------  -------------- -------------

  *Given the effect of cash in lieu of fractional shares
                                                                                                              80.06%         19.94%
</TABLE>
<PAGE>
<PAGE>
                                                               EXHIBIT 6.2A



September 22, 1998

VIA TELECOPIER TRANSMISSION TO 1 (626) 351-1188

Tetra Tech Canada Ltd.
and
Tetra Tech, Inc.
630 North Rosemead Blvd.
Pasadena, California
91107

Dear Sirs:

RE:  SENTREX AND TETRA TECH CANADA LTD.
- ---------------------------------------

We have acted as counsel to Leonard Stanmore, Liz Stanmore, Peter Nicoletti,
Silvana Nicoletti, Raymond Conroy, James Suen, Gord Hillis and Andre Greco (the
"Vendors") in connection with the sale by the Vendors to Tetra Tech Canada Ltd
(the "Purchaser") of all of the issued and outstanding share capital (the
"Purchased Shares") of each of 1056584 Ontario Limited, 1056585 Ontario Limited,
946489 Ontario Limited, Cen-Comm Communications Inc., Sentrex Electronics Inc.
and Venture Cable Ltd. (each a "Sentrex Company" and collectively the "Sentrex
Companies") and each of their subsidiaries (each a "Subsidiary" and collectively
the "Subsidiaries") pursuant to an agreement of purchase and sale (the "Sale
Agreement") made as of the 22nd day of September, 1998 among the Vendors, the
Purchaser and Tetra Tech, Inc.

This opinion is given pursuant to section 6.2 of the Sale Agreement.  We have
examined  certificates of status for the Sentrex Companies issued by the
Ministry of Consumer and Commercial Relations under the BUSINESS CORPORATIONS
ACT (Ontario) and have relied on such certificate as to those matters certified
therein. In addition, we have examined such statutes and other legislative
instruments, corporate documents and records and have made such other
investigations as we have deemed necessary in connection with the opinions
hereinafter set forth. In giving the opinions set forth herein, we assumed that
the Purchaser had the corporate power to enter into and perform all its
obligations under the Sale Agreement and have also assumed the due authorization
by all requisite corporate action of the execution, delivery and performance,
and the due execution and delivery of the Sale Agreement, by the Purchaser and
the validity and binding effect of the Sale Agreement on the Purchaser.

In our examination, we have assumed the authenticity of all documents submitted
to us as  originals, the genuineness of all signatures and the conformity to
originals of all documents submitted to us as certified or conformed copies or
facsimiles. We have not made any independent examination of the
<PAGE>
<PAGE>
Lipman, Zener and Waxman              -2-                    September 22, 1998

laws of any jurisdiction other than Canada and the Province of Ontario. We have
also assumed the legal capacity of the individual Vendors to execute and deliver
the documentation hereinafter referred to.

Based on and subject to the foregoing and relying on the foregoing to the extent
referred to above, we are of the opinion that:


1.   The Sale Agreement has been duly executed and delivered by each of the
Vendors and constitutes valid and binding obligations of the Vendors enforceable
in accordance with its terms subject to. (i) bankruptcy and other laws affecting
the enforcement of creditors' rights generally, and (ii) the discretion of a
court in granting equitable remedies including the remedy of specific
performance;

2.   Each of the Sentrex Companies is a corporation duly organized, validly
existing and in good standing under the laws of its jurisdiction of
incorporation and has all necessary corporate power and authority to own, lease,
and operate its properties and to carry on business

3.   The authorized capital stock of each Sentrex Company is as set forth on
Schedule 2.3 to the Sale Agreement. All of the outstanding shares of Common
Stock are duly authorized and validly issued, fully paid and nonassessable.

4.   Each Vendor is the record owner of the shares of each Sentrex Company set
out opposite such Vendor's name on Schedule 2.3 to the Sale Agreement;

5.   Each Vendor has all requisite legal power and authority to enter into the
Sale Agreement and the Employment, the Noncompetition Agreement and Registration
Rights Agreement and each Vendor has duly executed and delivered the Sale
Agreement, the Employment and Noncompetition Agreement and the Registration
Rights Agreement and such agreements constitute the legal, valid and binding
obligations of the Vendor, enforceable in accordance with their respective terms
subject to. (i) bankruptcy and other laws affecting the enforcement of
creditors' rights generally, and (ii) the discretion of a court in granting
equitable remedies including the remedy of specific performance;

6.   The execution and delivery by each Vendor of the Sale Agreement, the
Employment and Noncompetition Agreement or Noncompetition Agreement to which he
or she is a party and the Registration Rights Agreement, and the consummation by
each Vendor of the transactions contemplated thereby will not (i) violate, or be
in conflict with, or constitute a default (or other event which, with the giving
of notice or lapse of time or both, would constitute a default) under, or give
rise to any right of termination, cancellation or acceleration under any of the
terms, conditions or provisions of any material lease, license, promissory note,
contract, agreement, mortgage, deed of trust or other instrument or document
known to us to which the Vendor is a party or by which the Vendor or any of his
or her properties or assets may be bound, other than obligations to be
discharged on or immediately after Closing, (ii) violate any order, writ,
injunction or decree known to us, or any law, statute, rule or regulation of the
Province of Ontario or Canada applicable to the Vendor or any of his or her
properties or assets, or (iii) to the best of our knowledge, give rise to a
declaration or imposition of any claim, lien, charge, security interest or
encumbrance of any nature whatsoever upon the shares of Common Stock held by the
Vendor or upon any of the
<PAGE>
<PAGE>
Lipman, Zener and Waxman              -3-                    September 22, 1998

assets of any  Sentrex Company or any Subsidiary except for violations,
conflicts, breaches, liens, charges or encumbrances referred to in clauses (i)
through (iii) above as would not have a material adverse effect upon the
transactions contemplated by the Sale Agreement.

Yours very truly,

LIPMAN, ZENER & WAXMAN



Per:Bradley J. Miller
BJM:lgp
<PAGE>
<PAGE>
                                                               EXHIBIT 6.2B

September 22, 1998


Tetra Tech Canada Ltd.
670 N. Rosemead Boulevard
Pasadena, California  91107-2190

Ladies and Gentlemen:

          We have acted as special United States counsel to Raymond Conroy, Liz
Stanmore, Leonard Stanmore, Peter Nicoletti, Silvana Nicoletti, James Suen,
Gordon Hillis and Andre Greco for the purpose of providing to you certain
opinions in connection with the transactions contemplated by a Stock Purchase
Agreement, dated as of September 22, 1998, with you (the "Purchase Agreement").

          The opinions set forth in this letter are subject to the following
qualifications:

          1.   The opinions set forth in this letter are based solely upon (a)
our review of, as submitted to us, (i) the Articles of Incorporation, Bylaws and
records of the corporate proceedings of Sentrex Electronics USA, Inc. ("Sentrex
USA"), (ii) the Certificate of Incorporation, Bylaws and records of the
corporate proceedings of LAL Corp. ("LAL"), (iii) the governmental certificates
listed on Exhibit A attached to this letter (individually a "Governmental
Certificate"), (iv) an Officer's Certificate, dated the dated of this letter,
executed by the President of Sentrex USA (the "Sentrex USA Officer's
Certificate) and (v) an Officer's Certificate, dated the date of this letter,
executed by the Chief Executive Officer of LAL (the "LAL Officer's Certificate")
(items (i) through (v) being collectively the "Reviewed Documents"), (b) the
current recollection of those of our present attorneys who have had primary
responsibility for the incorporation and organization of Sentrex USA and LAL
(collectively the "Attorney Information") and (c) such review of published
sources of law as we have deemed necessary based solely upon our review of the
Reviewed Documents and the Attorney Information.  Other than our review of the
Reviewed Documents, we have made no inquiry or other investigation as to any
factual matter (including, but not limited to, (a) any review of any of the
files and other records of the Companies or any court or other governmental
authority or (b) any review of any of our files).

          2.   We have assumed without any inquiry or other investigation (a)
the legal capacity of each natural person, (b) the accuracy on the date of this
letter as well as on the date stated in any Governmental Certificate of each
statement as to any factual matter contained in such Governmental Certificate
and the accuracy on the date of this letter as well as on the date made of each
statement as to any factual matter contained in any other of the Reviewed
<PAGE>
<PAGE>
HODGSON, RUSS, ANDREWS, WOODS & GOODYEAR LLP

September 28, 1998
Page 2

Documents and (c) the genuineness of each signature on any of the Reviewed
Documents, the completeness of each of the Reviewed Documents, the authenticity
of each of the Reviewed Documents submitted to us as an original, the conformity
to the original of each of the Reviewed Documents submitted to us as a copy and
the authenticity of the original of each of the Reviewed Documents submitted to
us as a copy.

          3.   We do not express any opinion concerning any law other than the
Business Corporation Act of Illinois and the General Corporation Law of
Delaware.

          4.   To the extent that any opinion set forth in this letter is based
upon any statement contained in any Governmental Certificate, such opinion is
limited to the meaning ascribed to such statement by the issuer of such
Governmental Certificate.

          5.   Any opinion set forth in this letter (a) deals only with the
specific legal issue or issues it explicitly addresses and (b) does not address
any other matter.

          Subject to the qualifications set forth in this letter, it is our
opinion that:

          1.   Sentrex USA (a) is a corporation validly existing under the
Business Corporation Act of Illinois, (b) is in good standing in Illinois and
(c) has the corporate power to conduct its business as described in the Sentrex
USA Officer's Certificate and to own, lease and operate assets in connection
with such business.

          2.   The authorized capital stock of Sentrex USA is as set forth on
Schedule 2.3 to the Purchase Agreement.  All of the outstanding shares of common
stock of Sentrex USA are duly authorized, validly issued and, if fully paid,
nonassessable.

          3.   LAL (a) is a corporation validly existing under the General
Corporation Law of Delaware, (b) is in good standing in Delaware, (c) is duly
qualified to do business as a foreign corporation and in good standing in
Washington, Utah and Colorado and (d) has the corporate power to conduct its
business as described in the LAL Officer's Certificate and to own, lease and
operate assets in connection with such business.

          4.   The authorized capital stock of LAL is as set forth on Schedule
2.3 to the Purchase Agreement.  All of the outstanding shares of common stock of
LAL are duly authorized, validly issued and, if fully paid, nonassessable.
<PAGE>
<PAGE>
HODGSON, RUSS, ANDREWS, WOODS & GOODYEAR LLP

September 28, 1998
Page 3


          This letter is intended solely for your benefit and, without our
express written consent, may not be furnished to or relied upon, referred to or
otherwise used by any third party or relied upon, referred to or otherwise used
other than in connection with the transactions contemplated by the Purchase
Agreement.


                         Very truly yours,

                         HODGSON, RUSS, ANDREWS, WOODS & GOODYEAR, LLP


                    By   ____________________________________

                         Robert B. Fleming, Jr.
<PAGE>
<PAGE>
                                   EXHIBIT A

                           GOVERNMENTAL CERTIFICATES


1.   A certificate, dated September 18, 1998, from the Secretary of State of
     Illinois as to the corporate status of Sentrex USA in Illinois.

2.   A certificate, dated September 18, 1998, from the Secretary of State of
     Delaware as to the corporate status of LAL in Delaware.

3.   A certificate, dated September 21, 1998, from the Secretary of State of
     Washington as to the corporate status of LAL in Washington.

4.   A certificate, dated September 21, 1998, from the Secretary of State of
     the State of   Utah, as to the corporate status of LAL in Utah.

5.   A certificate, dated September 10, 1998, from the Secretary of State of
     the State of   Colorado, as to the corporate status of LAL in Colorado.
<PAGE>
<PAGE>
                                                               EXHIBIT 6.2C



                    EMPLOYMENT AND NONCOMPETITION AGREEMENT


          This Employment and Noncompetition Agreement (the "Agreement") is made
and entered into as of this 22nd day of September, 1998 by and among
____________________, an individual ("Shareholder"), Tetra Tech Canada Ltd., an
Ontario corporation ("TTC"), and Tetra Tech, Inc., a Delaware corporation
("Tetra Tech").


                                R E C I T A L S

          A.   Concurrently herewith, Shareholder, TTC and Tetra Tech are
consummating the transactions contemplated by that certain Stock Purchase
Agreement of even date (the "Stock Purchase Agreement").

          B.   This Agreement is the Employment and Noncompetition Agreement
referred to in SECTION 6.2 of the Stock Purchase Agreement, and pursuant
thereto, must be entered into by the parties hereto in connection with the
consummation of the transactions contemplated by the Stock Purchase Agreement.
The execution and performance of this Agreement is a substantial inducement to
Tetra Tech, TTC and Shareholder to enter into and consummate the transactions
contemplated by the Stock Purchase Agreement.

          C.   Shareholder, in connection with the Stock Purchase Agreement and
this Agreement, shall be compensated for the covenants contained herein, and
Shareholder is willing to refrain from competing with Tetra Tech and TTC as
provided herein.


                               A G R E E M E N T

          NOW, THEREFORE, in consideration of the mutual covenants and the
agreements hereinafter set forth, and in consideration of Tetra Tech, TTC and
Shareholder consummating the transactions contemplated by the Stock Purchase
Agreement, the parties hereto covenant and agree as follows:

          1.   COVENANT AGAINST COMPETITION; CONFIDENTIALITY AND DISCLOSURE.
Shareholder acknowledges that (i) the principal business to be acquired by TTC
pursuant to the Stock Purchase Agreement is site acquisition, planning, design,
construction, maintenance, equipment repair and support services associated with
the cable television and telephony
                                       1.
<PAGE>
<PAGE>
industries (such business being referred to as the "Business"); (ii) Shareholder
is one of a limited number of persons who has developed the Business conducted
by the Sentrex Companies (as defined in the Stock Purchase Agreement); (iii)
Shareholder's work has brought Shareholder, and Shareholder's employment with
TTC will continue to bring Shareholder, into close contact with many
confidential affairs not readily available to the public; and (iv) Tetra Tech
and TTC would not have consummated the transactions contemplated by the Stock
Purchase Agreement unless Shareholder entered into this Agreement.  Accordingly,
Shareholder covenants and agrees, that:

               (a)  Subject to SECTION 4(e) hereof, until the fourth anniversary
of the date hereof (the "Restricted Period"), Shareholder will not, within the
Geographic Area (as defined below), without the prior written consent of Tetra
Tech (1) compete directly or indirectly, or participate, directly or indirectly,
as agent, employee, consultant, representative or otherwise, or as a
stockholder, partner, member or joint venturer, or have any direct or indirect
financial interest, including, without limitation, the interest of a creditor,
in any enterprise engaging within the Geographic Area in the Business (as
defined above), or any business substantially similar to the Business; PROVIDED,
HOWEVER, that Shareholder may own, directly or indirectly, solely as an
investment, securities of any entity which are traded on any U.S. or Canadian
securities exchange if Shareholder (A) is not a controlling person of or a
member of a group which controls such entity and (B) does not, directly or
indirectly, own 5% or more of any class of securities of such entity; or (2)
engage in the Business or any business substantially similar to the Business for
Shareholder's own account.

               (b)  During and after the Restricted Period, Shareholder shall
keep secret and retain in strictest confidence, and shall not use for the
benefit of Shareholder or others except in connection with the business and
affairs of Tetra Tech and TTC and their respective subsidiaries and affiliates,
all non-public matters relating to the Business and to Tetra Tech and TTC and
their respective subsidiaries and affiliates, including, without limitation, and
to the extent confidential, trade secrets, "know-how," client lists,
subscription lists, details of contracts, pricing policies, operational methods,
marketing plans or strategies, business acquisition, disposition or
reorganization plans, requisition forms or procedures, software programs, new
personnel acquisition plans, technical processes, designs and design projects,
inventions and research projects, technical services, and other business affairs
relating to, arising from or in connection with the Business or to Tetra Tech
and TTC and their respective subsidiaries and affiliates learned by Shareholder
heretofore or hereafter, and shall not disclose them to anyone outside of Tetra
Tech and TTC and their respective subsidiaries and affiliates, either during or
after retention as an employee by Tetra Tech or TTC or any of their respective
subsidiaries and affiliates, except as required in the course of performing
duties hereunder, by law, or with Tetra Tech's express written consent.  For
purposes of this Agreement, confidential information concerning Tetra Tech and
TTC shall not include any information which (i) at the time of disclosure or
thereafter is generally available to and known by the public (other than as a
result of the disclosure directly or indirectly by
                                       2.
<PAGE>
<PAGE>
Shareholder) or (ii) has been independently acquired or developed by Shareholder
without violating any of Shareholder's obligations under this Agreement.

               (c)  During the Restricted Period, Shareholder shall not,
directly or indirectly, (i) solicit or encourage to leave the employment or
service of Tetra Tech and TTC or any of their respective subsidiaries or
affiliates, any employee or consultant of Tetra Tech and TTC or any of their
respective subsidiaries or affiliates, or (ii) hire or retain any employee or
consultant who is employed or retained by, or who, within one year prior to the
date of solicitation or encouragement, has left the employment or service of,
Tetra Tech and TTC or any of their respective subsidiaries or affiliates to
engage in the Business or any business substantially similar to the Business.

               (d)  The parties agree that due to the nature of TTC's Business
operations from and after the date hereof as a service provider throughout
Canada and the United States, due to the fact that such services can be
performed throughout the world and due to the nature of Tetra Tech's business
operations as a service provider throughout the world and its intention to
extend the Business throughout the world in connection with the transactions
contemplated by the Stock Purchase Agreement, in order for this Agreement to be
meaningful it must restrict Shareholder from competing with the Business
throughout Canada, the United States and the world.  Therefore, the parties
agree that for the purposes of this Agreement, "Geographic Area" shall mean (i)
each and every province and territory of Canada, (ii) the District of Columbia
and each and every county of each and every state, commonwealth and territory of
the United States, and (iii) each and every country and territory throughout the
world in which TTC, Tetra Tech, or any subsidiary or affiliate thereof, engages
in the Business at any time during the Restricted Period.

          2.   RIGHTS AND REMEDIES UPON BREACH OF THE RESTRICTIVE COVENANTS.

               (a)  Shareholder recognizes that Tetra Tech and TTC do not have
an adequate remedy at law to protect their respective rights hereunder.
Accordingly, Shareholder agrees that Tetra Tech and TTC shall have the right to
an injunction without bond in any court of competent jurisdiction permanently
enjoining Shareholder from a violation of SECTION 1 hereof (the "Restrictive
Covenants").

               (b)  Shareholder recognizes and agrees that in the event of a
violation of any of the Restrictive Covenants, the period during which
Shareholder shall not compete shall be suspended during the period Shareholder
is engaged in conduct constituting such violation and shall resume after such
violation has been remedied to the satisfaction of Tetra Tech and TTC.
                                       3.
<PAGE>
<PAGE>
               (c)  Tetra Tech and TTC shall provide notice to Shareholder, in
the manner provided in SECTION 5 hereof, at such time as (i) a suspension is in
effect and (ii) the violation has been remedied to the satisfaction of Tetra
Tech and TTC.

               (d)  The remedies set forth in SUBPARAGRAPH (a) above shall not
limit, eliminate, prohibit or restrict any other rights that Tetra Tech and TTC
may have under law for violation by Shareholder of this Agreement and shall not
be mutually exclusive and any one or all may be pursued without the pursuit of
one impairing or precluding the pursuit of another.

          3.   SEVERABILITY OF RESTRICTIVE COVENANTS.  It is understood and
agreed by the parties hereto that the provisions of each of the preceding
sections of this Agreement are independent of and severable from each other and
the invalidity of any section or any portion thereof shall not affect the
validity or hinder the enforceability of the remaining provisions of this
Agreement.  The parties expressly agree and declare that the time limitation and
geographic scope set forth in SECTION 1 hereof are reasonable, are properly
required for the adequate protection of the business of Tetra Tech and TTC and
that in the event such time limitation and/or geographic scope is deemed to be
unreasonable by the final decision of an arbitrator or a court of competent
jurisdiction, Tetra Tech, TTC and Shareholder agree to submit to such revision
or modification thereof as said arbitrator or court shall deem reasonable.

          4.   AGREEMENTS REGARDING EMPLOYMENT.

               (a)  For so long as Shareholder is an employee of TTC or any of
its affiliates, TTC shall pay or provide, and Tetra Tech shall cause TTC to pay
or provide, to Shareholder the following:

                    (i)    an annual base salary of $_________ Canadian Dollars*
to serve in the capacity of __________________**.  In consideration of such
salary, Shareholder shall devote his full business time and attention to the
operation of TTC's business;

- -----------------------------
          *    $271,800 for Stanmore; $250,000 for Nicoletti; $196,000 for
Conroy; $189,000 for Suen; $70,000 for Brooks; and $90,000 for Greco.

          **   President for Stanmore; Vice President for Nicoletti; Vice
President for Conroy; Operations Director for Suen; Manager for Brooks; and
Manager for Greco.
                                       4.
<PAGE>
<PAGE>
                    (ii)   employee benefits that are consistent with those
provided on the date hereof to Shareholder; and

                    (iii)  reimbursement for reasonable business expenses
actually incurred or paid by him, consistent with the policies of TTC, in
rendering the services provided for hereunder, upon presentation of expense
statements or such other supporting information as TTC may customarily require
of its executives.

               (b)  Shareholder's principal place of employment shall be at the
principal offices of TTC located in Toronto, Ontario, Canada; provided, however,
that Shareholder may be required to perform certain duties in Denver, Colorado;
Salt Lake City, Utah; Seattle, Washington; or Chicago, Illinois.

               (c)  For so long as Shareholder is an employee of TTC or any of
its affiliates, Shareholder shall be entitled to participate in and receive
benefit under Tetra Tech's annual bonus plan for TTC and its subsidiaries (the
"Bonus Plan").   Under the Bonus Plan, bonuses will not be payable unless TTC
and its subsidiaries achieve, commencing with the fiscal year beginning on
October 5, 1998, annual Operating Profit (as hereinafter defined) of at least
$11,250,000 U.S. Dollars.  The Bonus Plan shall consist of a pool determined by
multiplying the Operating Profit, if it exceeds $11,250,000 U.S. Dollars, from
TTC and its subsidiaries for any fiscal year in excess of 6.5% of TTC's and its
subsidiaries' gross revenues for such fiscal year by 25%.  For purposes of this
SUBPARAGRAPH (b), "Operating Profit" is defined as income from the operations of
the Sentrex Companies (as defined in the Stock Purchase Agreement) acquired by
TTC pursuant to the Stock Purchase Agreement, including all income from
Whalen/Sentrex LLC or its successor, after consideration of the payment of all
bonuses to the employees of TTC and its subsidiaries for the applicable period,
before income taxes and interest income/expense.  For purposes of determining
Operating Profit, overhead, administrative or similar charges of Tetra Tech
shall be charged to TTC in accordance with Tetra Tech's normal policies;
PROVIDED, HOWEVER, that such charges will not exceed a reasonable allocation
consistent with Tetra Tech's allocations to its other business units.  The bonus
payable to Shareholder shall be determined by TTC, subject to approval by Tetra
Tech.

               (d)  TTC may terminate Shareholder's employment for any reason or
no reason and with or without cause, upon providing the greater of 30 days prior
written notice to Shareholder, or any entitlements under the ONTARIO EMPLOYMENT
STANDARDS ACT  notice or severance, whichever is greater.  Shareholder may
terminate his employment hereunder for any reason or no reason upon 30 days
prior written notice to TTC.  Upon the termination of Shareholder's employment
hereunder, Shareholder shall be entitled to, and TTC's obligations hereunder
shall be limited to, the payment of the compensation accrued under SUBPARAGRAPHS
(a) and (c) hereof to the effective date of such termination.
                                       5.
<PAGE>
<PAGE>
               (e)  In the event that Shareholder's employment hereunder is
terminated by TTC other than "for cause" (as defined below), then (i)
Shareholder shall not be subject to the restrictions set forth in SECTION 1(a)
hereof as of the date of termination and (ii) Shareholder shall have the right
to use the confidential information described in SECTION 1(b) hereof solely for
purposes of his subsequent employment.  For purposes of this Agreement,
Shareholder shall be deemed to have been terminated by TTC "for cause" in any
case where Shareholder repeatedly neglects or fails to perform his duties after
written notice thereof from TTC, breaches any material covenants or undertakings
hereunder or under the Stock Purchase Agreement, or commits any material act not
approved of or ratified by TTC knowingly involving any conflict of interest or
self-dealing relating to any aspect of TTC, Tetra Tech or any affiliate thereof.

          5.   NOTICES.  Any notice or other communication required or permitted
hereunder will be in writing and will be deemed sufficiently given only if
delivered in person or sent by registered airmail letter, postage prepaid, or by
facsimile transmission followed by U.S. or Canadian Mail, addressed as follows:

               (a)  If to Tetra Tech or TTC:

                         Tetra Tech, Inc.
                         670 N. Rosemead Boulevard
                         Pasadena, California  91107-2190
                         Attention:  Dr. Li-San Hwang
                         Facsimile:  (818) 351-1188

               (b)  If to Shareholder:

                         _________________________
                         _________________________
                         _________________________
                         _________________________
                         Facsimile:  _____________

or to such other address or facsimile number as any of the persons designated
above may have specified in a notice or communication duly given to the other
designated person as provided herein.  Such notice or communication will be
deemed to have been given as of the date so delivered or telecopied, or if
mailed, two days thereafter.

          6.   ASSIGNABILITY.  This Agreement shall be binding upon and inure to
the benefit of Tetra Tech and TTC, and their respective assigns and successors.
This Agreement shall not be assignable by Shareholder.
                                       6.
<PAGE>
<PAGE>
          7.   ENTIRE AGREEMENT.  This Agreement contains the entire agreement
among Shareholder, Tetra Tech and TTC with respect to the subject matter hereof.

          8.   WAIVERS, AMENDMENTS AND FURTHER AGREEMENTS.  Neither this
Agreement nor any term or condition hereof, including without limitation the
terms and conditions of this SECTION 8, may be waived, modified or amended in
whole or in part as against Tetra Tech, TTC or Shareholder except by written
instrument executed by each of the parties expressly stating that it is intended
to operate as a waiver, modification or amendment of this Agreement or the
applicable term or condition hereof.  Each of the parties hereto agrees to
execute all such further instruments and documents and to take all such further
action as the other party may reasonably require in order to effectuate the
terms and purposes of this Agreement.

          9.   COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, but all of which shall
constitute one and the same instrument.

          10.  GOVERNING LAW.  This Agreement shall be governed by and construed
and enforced in accordance with the laws of the State of California.

          11.  ARBITRATION.  Any controversy between the parties to this
Agreement involving the construction or application of any element of this
Agreement (including but not limited to those regarding calculation of amounts
due under the Bonus Plan, but excluding injunction actions contemplated by
SECTION 2(a)) shall be submitted to arbitration on the written request of either
party served on the other party.  The arbitration shall be held in Denver,
Colorado and conducted in accordance with the then current Commercial
Arbitration Rules of the American Arbitration Association.  Judgment upon the
award may be entered in any court of competent jurisdiction or application may
be made to such court for a judicial acceptance of the award and an order of
enforcement, as the case may be.

          12.  ATTORNEYS' FEES.  In the event of arbitration or litigation
arising out of or related to this Agreement, the prevailing party shall be
entitled to reimbursement of its reasonable attorneys' fees and costs of suit in
addition to such other relief as may be granted,
                                       7.
<PAGE>
<PAGE>
including but not limited to such fees and costs incurred in collections and in
enforcement and appeal of any judgment that may be rendered.

          IN WITNESS WHEREOF, the parties hereto have executed or caused to be
executed this Agreement as of the date first above written.

                                        TETRA TECH, INC.


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


                                        TETRA TECH CANADA LTD.


                                        By:  ________________________________
                                             Li-San Hwang
                                             President



                                        SHAREHOLDER


                                        _____________________________________

                                       8.
<PAGE>
<PAGE>
                                                               EXHIBIT 6.2D



                         REGISTRATION RIGHTS AGREEMENT



          This Registration Rights Agreement (the "Agreement") is entered into
as of September 22, 1998 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, Tetra Tech Canada Ltd., an Ontario corporation
("TTC"), and the Holders are parties to a Stock Purchase Agreement dated as of
the date hereof (the "Stock Purchase Agreement"); and

          B.   Pursuant to the Stock Purchase Agreement, the Holders will
receive shares of TTC which are exchangeable for 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 Stock Purchase Agreement and, pursuant thereto, must be
entered into by the parties in connection with 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>
<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 6.

               "REGISTRABLE SECURITIES" shall mean the shares of Tetra Tech
Common Stock (i) issued upon exchange for the shares of TTC held by the Holders
pursuant to the Stock Purchase Agreement and the exhibits thereto, 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 in
a private transaction (excluding the issuance of the Tetra Tech Common Stock
pursuant to the Stock Purchase Agreement).

               "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 145" shall mean Rule 145 promulgated under the Securities
Act, or any similar successor rule, as the same shall be in effect from time to
time.
                                       2
<PAGE>
<PAGE>
               "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.

               "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 use all commercially reasonable efforts to
file a Registration Statement on Form S-1, Form S-2 or Form S-3, whichever Tetra
Tech shall be eligible to use, 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, on or before February 27, 1999, to cause such
Registration Statement to become effective not later than April 15, 1999, and to
keep such Registration Statement continuously effective for a period ending on
the date on which all Holders are eligible to sell Registrable Securities under
Rule 144 without any volume limitation (or similar successor Rule).

               (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 may reasonably request in connection with such Registration
Statement.

               (c)  Notwithstanding the foregoing, one-time only, for a period
not to exceed 90 days, Tetra Tech shall not be obligated to prepare and file, or
be prevented from delaying, the effectiveness of the Registration Statement
required hereunder if Tetra Tech, in its good faith judgment, reasonably
believes that the filing or maintenance 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 (A) a pending or scheduled public offering or private placement
of securities of Tetra Tech, (B) an acquisition, merger, consolidation or
similar transaction by or of Tetra Tech, (C) preexisting and continuing
negotiations, discussions or pending proposals with respect to any of the
foregoing transactions, or (D) 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,
                                       3
<PAGE>
<PAGE>

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.

          No seller of Registrable Securities shall (until further notice)
effect sales of shares covered by the Registration Statement after receipt of
telegraphic, telecopied or written notice from Tetra Tech to suspend sales to
permit Tetra Tech to correct or update a registration statement or prospectus.

          3.   REGISTRATION PROCEDURES.  In connection with Tetra Tech's
registration obligations pursuant to SECTION 2 hereof, Tetra Tech will use its
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;

               (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)  promptly 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
                                       4
<PAGE>
<PAGE>
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)  furnish to each selling Holder, without charge, at least one
signed copy of the Registration Statement and any post-effective amendment
thereto, including financial statements and schedules, all documents
incorporated therein by reference and all exhibits (including those incorporated
by reference);

               (f)  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;

               (g)  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 its
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;

               (h)  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;

               (i)  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
                                       5
<PAGE>
<PAGE>
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;

               (j)  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;

               (k)  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;

               (l)  use its commercially reasonable 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

               (m)  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.

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(i) 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

                                       6
<PAGE>
<PAGE>

accountants of Tetra Tech (including the expenses of any special audit required
by or incident to such performance), the fees 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 (y)
based upon written information furnished to Tetra Tech by such Holder expressly
for the inclusion in such Registration Statement, 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
                                       7
<PAGE>
<PAGE>
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
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
                                       8
<PAGE>
<PAGE>
indemnified party as a result of such losses, claims, damages, liabilities or
expenses (i) in such proportion as is appropriate to reflect the relative
benefits received by the indemnifying party on the one hand and the indemnified
party on the other, or (ii) if the allocation provided by CLAUSE (i) above is
not permitted by applicable law or provides a lesser sum to the indemnified
party than the amount hereinafter calculated, in such proportion as is
appropriate to reflect not only the relative benefits received by the
indemnifying party on the one hand and the indemnified party on the other but
also the relative fault of the indemnifying party and the indemnified party as
well as any other relevant equitable considerations.  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 7 shall remain in full force and effect, regardless of
any investigation made by or on behalf of a participating Holder, its officers,
directors, partners, attorneys, agents or any person, if any, who controls 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 lawfully 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
<PAGE>
<PAGE>
          7.   RULE 144.   Tetra Tech covenants that it will use its best
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
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 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.
                                       10
<PAGE>
<PAGE>
          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 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 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.

          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.
                                       11
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<PAGE>
          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.

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


                                        TETRA TECH, INC.


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


                                        _______________________________________
                                        Raymond Conroy


                                        _______________________________________
                                        Elizabeth Stanmore


                                        _______________________________________
                                        Leonard Stanmore


                                        _______________________________________
                                        Peter Nicoletti


                                        _______________________________________
                                        Silvana Nicoletti


                                        _______________________________________
                                        James Suen

                                       12
<PAGE>
<PAGE>



                                        _______________________________________
                                        Gordon Brooks


                                        _______________________________________
                                        Andre Greco

                                       13
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<PAGE>
                                                                 SCHEDULE A

                              SCHEDULE OF HOLDERS

                                         Number of Shares of Tetra Tech
                                              Common Stock Issuable
Holder's Name/Address/Facsimile No.           Upon Exchange Pursuant
                                         To the Stock Purchase Agreement
- -----------------------------------   -------------------------------------

     Raymond Conroy                        156,386 shares
     303 Dods Crescent
     Alton, Ontario
     L0N 1A0
     Facsimile:  (905) 459-9686

     Elizabeth Stanmore                    79,598 shares
     26 Grand Oaks Crescent
     Brampton, Ontario
     L6Z 3K7
     Facsimile:  (905) 459-9686

     Leonard Stanmore                      372,010 shares
     26 Grand Oaks Crescent
     Brampton, Ontario
     L6Z 3K7
     Facsimile:  (905) 459-9686

     Peter Nicoletti                       239,036 shares
     101 Flushing Avenue
     Woodbridge, Ontario
     L4L 3H9
     Facsimile:  (905) 459-9686

     Silvana Nicoletti                     4,713 shares
     101 Flushing Avenue
     Woodbridge, Ontario
     L4L 3H9
     Facsimile:  (905) 459-9686

     James Suen                            62,251 shares
     5812 Fieldon Road
     Mississauga, Ontario
     L5M 5K1
     Facsimile:  (905) 459-9686

     Gordon Brooks                         2,827 shares
     520 Fralicks Beach Road
     Port Perry, Ontario

     Andre Greco                           3,533 shares
     3472 Church Street
     Blackstock, Ontario
     L0B 1B0
     Facsimile:  (905) 459-9686
<PAGE>
<PAGE>
                                                                  EXHIBIT 6.2E





                               September 22, 1998



To the Shareholders of the Sentrex Companies


     Re:  Stock Purchase Agreement dated September 22, 1998
          by and among Tetra Tech, Inc., Tetra Tech Canada Ltd. and
          the Shareholders of the Sentrex Companies (the "Agreement")
          -------------------------------------------------------------

Ladies and Gentlemen:

     We have acted as counsel to Tetra Tech, Inc., a Delaware corporation
("Tetra Tech"), in connection with the acquisition of the outstanding shares of
capital stock of the Sentrex Companies pursuant to the Agreement.  Unless
otherwise defined herein, capitalized terms used herein shall have the meanings
assigned to them in the Agreement.  This opinion is rendered pursuant to Section
6.2 of the Agreement.

     In connection with this opinion, we have examined and relied upon the
following documents:

     (a)  an originally executed counterpart of the Agreement;

     (b)  an originally executed counterpart of each Employment and
Noncompetition Agreement;

     (c)  an originally executed counterpart of the Registration Rights
Agreement;

     (d)  the Certificate of Incorporation and Bylaws of Tetra Tech, and all
amendments thereto; and

     (e)  a certified copy of the resolutions adopted by the Board of Directors
of Tetra Tech authorizing the execution and delivery by Tetra Tech of the
Agreement and all other documents executed and delivered by Tetra Tech in
connection therewith and the transactions contemplated thereby.
<PAGE>
<PAGE>
To the Shareholders of the Sentrex Companies
September 22, 1998
Page 2

     We have also examined such other documents as we have deemed necessary or
appropriate as a basis for the opinions set forth below.  In our examination, we
have assumed the genuineness of the signatures of all parties other than those
on behalf of Tetra Tech, the legal capacity of all natural persons, the
authenticity of all documents submitted to us as originals, the conformity to
original documents of all documents submitted to us as certified or photostatic
copies, and the authenticity of the originals of such copies.  As to any facts
relevant to this opinion, we have relied upon certificates, statements and
representations of Tetra Tech and certificates and other advices of public
officials.

     We have also assumed, for purposes of the opinions expressed herein, that
each of the Shareholders has the power, authority and capacity to enter into and
perform the Agreement, their respective Employment and Noncompetition Agreements
and the Registration Rights Agreement and that the Agreement, the Employment and
Noncompetition Agreements and the Registration Rights Agreement have been duly
authorized, executed and delivered by each of the Shareholders, and constitute
the legal, valid and binding obligations of each of the Shareholders enforceable
against each of them in accordance with their respective terms.

     We have investigated such questions of law for the purposes of rendering
this opinion as we have deemed necessary.  We are attorneys duly admitted and
qualified to practice in the State of California and we are only opining herein
as to the effect on the subject transactions of United States federal law, the
law of the State of California and the General Corporation Law of the State of
Delaware (the "Corporation Law"), as such laws are in effect on the date of this
opinion.  We are not opining on, and assume no responsibility as to, the
applicability to or the effect on any of the matters covered herein of the laws
of any other jurisdiction.  In particular, we express no opinion with respect to
(i) state securities or "blue sky" laws, or (ii) federal or state antifraud laws
(whether arising under federal or state securities laws or otherwise).

     In our opinion expressed in paragraph 1 with respect to foreign
qualifications, we have relied solely upon certain standard compilations of the
applicable statutes of states other than California which we believe are current
and which may be subject to judicial or regulatory interpretations and
modifications, and such opinions are expressly qualified to the extent that such
compilations are not fully current or do not reflect such judicial or regulatory
interpretations or modifications.  The opinions set forth herein are given as of
the date hereof, and we assume no responsibility to update such opinions for
events that may occur after such date.

     On the basis of the foregoing and in reliance thereon, we are of the
opinion that:
<PAGE>
<PAGE>
To the Shareholders of the Sentrex Companies
September 22, 1998
Page 3

     1.   Tetra Tech is a corporation duly organized, validly existing and in
good standing under the laws of the State of Delaware and has the requisite
corporate power and authority to own, lease and operate its properties, and to
carry on its business as such is now being conducted.  Tetra Tech is duly
qualified to transact business and is in good standing in each jurisdiction in
which the character of its business makes such qualification necessary, except
for such jurisdictions where the failure to be so qualified would not have a
material adverse effect on the financial condition, results of operations or
business of Tetra Tech and its subsidiaries, considered as a whole (a "Material
Adverse Effect").

     2.   Tetra Tech has all requisite corporate power and authority to execute
and deliver the Agreement, and the Employment and Noncompetition Agreements and
Registration Rights Agreement (collectively, the "Related Agreements"), and to
consummate the transactions and to perform its obligations contemplated thereby.
Tetra Tech has taken all necessary corporate action to authorize the execution
and delivery of the Agreement and the Related Agreements, and the performance of
its obligations thereunder.  Each of the Agreement and the Related Agreements
has been duly executed and delivered by Tetra Tech, and each is the valid and
binding obligation of Tetra Tech, enforceable against Tetra Tech in accordance
with its respective terms.

     3.   The authorized capital stock of Tetra Tech is as set forth in Section
4.2 of the Agreement.  All of the outstanding shares of Tetra Tech Common Stock
have been duly authorized and are validly issued, and are fully paid and
nonassessable.  To the best of our knowledge, except for (i) the transactions
contemplated by the Agreement, (ii) stock options granted or to be granted to
Tetra Tech's officers, directors, employees, consultants and advisors pursuant
to any Tetra Tech stock option plan, or (iii) shares to be issued under Tetra
Tech's Employee Stock Purchase Plan, there are no outstanding options, warrants,
convertible debt or securities, calls, agreements, arrangements, commitments,
understandings or other rights to purchase any of Tetra Tech's capital stock, or
securities convertible into or exchangeable for any such capital stock.  The
shares of Tetra Tech Common Stock to be issued pursuant to the Agreement will,
upon consummation of the transactions contemplated therein, be duly authorized,
validly issued, fully paid and nonassessable.

     4.   The execution and delivery by Tetra Tech of the Agreement and the
Related Agreements, and the consummation by Tetra Tech of the transactions
contemplated thereby, will not (i) violate any provision of the Certificate of
Incorporation or Bylaws of Tetra Tech, (ii) violate, or be in conflict with, or
constitute a default (or other event which, with the giving of notice or lapse
of time or both, would constitute a default) under, or give rise to any right of
termination, cancellation or acceleration under any of the terms, conditions or
provisions of, any
<PAGE>
<PAGE>
To the Shareholders of the Sentrex Companies
September 22, 1998
Page 4

material lease, license, promissory note, contract, agreement, mortgage, deed of
trust or other instrument or document known to us to which Tetra Tech is a party
or by which Tetra Tech or any of its properties or assets may be bound, (iii) to
the best of our knowledge, violate any order, writ, injunction or decree known
to us, or any law, statute, rule or regulation of the State of California, the
United States or the Corporation Law applicable to Tetra Tech or any of its
properties or assets, or (iv) to the best of our knowledge, give rise to a
declaration or imposition of any claim, lien, charge, security interest or
encumbrance of any nature whatsoever upon any of the assets of Tetra Tech's
businesses, except for such violations, conflicts, breaches, liens, charges or
encumbrances referred to in clauses (ii) through (iv) above as would not have a
Material Adverse Effect.

     5.   To the best of our knowledge, no approvals or consents by, or filings
with, any federal, state, municipal, foreign or other court or governmental or
administrative body, agency or other third party is required in connection with
the execution and delivery by Tetra Tech of the Agreement and the Related
Agreements, or the consummation by Tetra Tech of the transactions contemplated
thereby, except for those approvals, consents and filings which, if not
obtained, would not have a material adverse impact on the ability of Tetra Tech
to perform its business as currently conducted or on the ability of Tetra Tech
to execute and deliver the Agreement and the Related Agreements, or to
consummate the transactions contemplated thereby.

     6.   To the best of our knowledge, there is no pending or threatened
action, suit, arbitration proceeding, investigation or inquiry before any court
or governmental or administrative body or agency, or any private arbitration
tribunal, against, relating to or affecting (i) Tetra Tech or any director,
officer or employee of Tetra Tech in his or her capacity as such, or the assets,
properties or business of Tetra Tech, which would, if decided adversely, have a
Material Adverse Effect, or (ii) the transactions contemplated by the Agreement.

     Our opinions expressed in paragraph 2 are subject to and limited by the
following:

               (i)    the effect of (A) applicable bankruptcy, insolvency,
reorganization, oratorium, fraudulent conveyance, fraudulent transfer and other
similar laws affecting the rights of creditors generally, and (B) principles of
equity, regardless of whether the enforcement is sought in a proceeding at law
or in equity;

               (ii)   the effect of court decisions, invoking statutes or
principles of equity, which have held that certain covenants and provisions of
agreements are unenforceable where enforcement of such covenants or provisions
under the circumstances would violate the enforcing party's implied covenant of
good faith and
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<PAGE>
To the Shareholders of the Sentrex Companies
September 22, 1998
Page 5


fair dealing or which subject the enforceability of such covenants or provisions
under such circumstances to notions of materiality, reasonableness or impairment
of security;

               (iii)  the enforceability under certain circumstances of any
provision in any document expressly or by implication waiving broadly or vaguely
stated rights, unknown future rights, or defenses to obligations or rights
granted by law, when such waivers are against public policy or prohibited by
law;

               (iv)   the unenforceability under certain circumstances of any
provision in any document to the effect that rights or remedies are not
exclusive, that rights or remedies may be exercised without notice, that every
right or remedy is cumulative and may be exercised in addition to or with any
other right or remedy, that election of a particular remedy or remedies does not
preclude recourse to one or more remedies, or that failure to exercise or delay
in exercising rights or remedies will not operate as a waiver of any such right
or remedy;

               (v)    the unenforceability under certain circumstances of any
provision in any document indemnifying a party against, or requiring
contributions toward, that party's liability for its own wrongful or negligent
acts, or where indemnification or contribution is contrary to public policy;

               (vi)   the unenforceability of any provision in any document
relating to payment or reimbursement of attorneys' fees in excess of statutory
limits or an amount determined to be reasonable by any court or other tribunal;

               (vii)  the effect on enforceability of rights and remedies
resulting from certain procedural requirements, such as statutes of limitation,
the required format and timing of service of process, court filings, recordation
and notices which must meet the minimum statutory requirements; and

               (viii) the unenforceability of any provisions regarding covenants
not to compete which conflict with Section 16600 et seq. of the California
Business and Professions Code relating to the invalidity of contracts by which a
party is restrained from engaging in a lawful profession, trade or business of
any kind.

     As used in this opinion, the expression "to the best of our knowledge,"
"known to us" or similar language with reference to matters of fact means that,
during the course of our representation of Tetra Tech, no information that would
give us current actual knowledge of the
<PAGE>
<PAGE>
To the Shareholders of the Sentrex Companies
September 22, 1998
Page 6

inaccuracy of such statement has come to our attention.  Further, the expression
"to the best of our knowledge," "known to us" or similar language with reference
to matters of fact refers to the current actual knowledge of the attorneys of
this firm who have worked on matters for Tetra Tech solely in connection with
the Agreement and the transactions contemplated thereby.  Except to the extent
expressly set forth herein, we have not undertaken any independent investigation
to determine the existence or absence of any fact, and no inference as to our
knowledge of the existence or absence of any fact should be drawn from our
representation of Tetra Tech or the rendering of the opinions set forth herein.

     We advise you that certain principals and other persons associated with
this firm own shares of Tetra Tech Common Stock.

     This opinion has been rendered solely for your use in connection with the
transactions contemplated by the Agreement and may not be relied upon by any
other person for any reason whatsoever.

                                   Very truly yours,





















<PAGE>
<PAGE>

                                                               EXHIBIT 6.2F


                                        September 22, 1998


Shareholders of the Sentrex Companies


Dear Sirs/Mesdames:

          Re:  Stock Purchase Agreement dated September 22, 1998 by and
               among Tetra Tech, Inc., Tetra Tech Canada Ltd. and the
               Shareholders of the Sentrex Companies (the "Agreement")
               --------------------------------------------------------

     We have acted as special counsel to Tetra Tech Canada Ltd. ("TTC") in
connection with the purchase of the outstanding shares of the Sentrex Companies
pursuant to the Agreement.  Unless otherwise defined herein, terms used in this
opinion that are defined in the Share Purchase Agreement and used herein as so
defined.

     We have examined:

     (a)  a copy of the Agreement;

     (b)  a copy of the Support Agreement (the "Support Agreement") of even date
herewith between Tetra Tek and TTC;

     (c)  the articles of incorporation of TTC, including the Exchangeable Share
Provisions;

     (d)  a copy of a directors resolution of TTC authorizing the execution and
delivery of the Agreement and the Support Agreement and the issuance of the
Exchangeable Shares.

     We have also examined originals or copies, certified or otherwise
identified to our satisfaction, of such other instruments and documents and we
have considered such questions of law as we have deemed relevant and necessary
as a basis for the opinions
<PAGE>
<PAGE>

                                      -2-

hereinafter expressed.  In such examinations we have assumed the genuineness of
all signatures, the authenticity of all documents submitted to us as originals
and the conformity to original documents of all documents submitted to us as
copies, whether facsimile, photostatic, certified or otherwise.

     We have also assumed that each of the Agreement and the Support Agreement
has been duly authorized, executed and delivered by and constitutes a valid and
legally binding obligation of each of the parties thereto other than TTC,
enforceable against each of those parties in accordance with the respective
terms thereof.  We have also assumed that insofar as any obligation under the
Agreement or the Support Agreement is to be performed in any jurisdiction
outside the Province of Ontario, its performance will not be illegal or
unenforceable by virtue of the laws of that other jurisdiction.

     Based and relying upon the foregoing and subject to the qualifications
hereinafter expressed, we are of the opinion that:

1.   TTC is a corporation incorporated and subsisting under the laws of the
Province of  Ontario.

2.   The authorized capital of TTC consists of an unlimited number of common
shares and 920,354 Exchangeable Shares of which 1,000 common shares and 920,354
Exchangeable Shares have been issued and are outstanding.

3.   The articles of TTC contain no restrictions on the business that TTC may
carry on or on the powers that TTC may exercise.

4.   The execution, delivery and performance of each of the Agreement and the
Support Agreement have been duly authorized by all necessary corporate action on
the part of TTC.

5.   Each of the Agreement and the Support Agreement constitutes a valid and
legally binding obligation of TTC, enforceable against TTC in accordance with
its terms.

     The opinions expressed above are subject to the following qualifications:

     (A)  this opinion is limited to the laws of the Province of Ontario and the
laws of Canada applicable therein;

     (B)  the enforceability of each of the Agreement and the Support Agreement
is subject to applicable bankruptcy, insolvency, reorganization and other laws
of general application limiting the enforcement of creditors' rights generally
<PAGE>
<PAGE>
                                      -3-

and to the fact that equitable remedies, such as injunction and specific
performance, are available only in the discretion of the court;

     (C)  statutory limitation of the time within which proceedings may be
brought;

     (D)  the validity and enforceability of provisions inserted in any
agreement or instrument that purport to sever from the agreement or instrument
any provision that is prohibited or unenforceable under applicable law without
affecting the enforceability or validity of the remainder of the agreement or
instrument would be determined only in the discretion of the court.

     This opinion is furnished solely for the benefit of the Shareholders in
connection with the purchase of the Shares by TTC and may not be circulated to
or relied upon by any other person or used for any other purpose.

                                        Yours very truly,



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