<PAGE>   1
                                                                  EXHIBIT 10(ii)



                           STOCK REDEMPTION AGREEMENT
                           --------------------------


         AGREEMENT dated as of June 26 1998, between Quanterra Incorporated, a
Delaware corporation with a principal place of business at 5251 DTC Parkway,
Suite 415, Englewood, Colorado 80111 ("Quanterra"), IT Corporation, a California
corporation with a principal place of business at 2790 Mosside Boulevard,
Monroeville, Pennsylvania 15146 ("IT"), and International Technology Corporation
("ITX"), a Delaware corporation with a principal place of business at 2790
Mosside Boulevard, Monroeville, Pennsylvania 15146.

                                  INTRODUCTION:

         IT owns certain shares of the common stock in Quanterra, a company
engaged in certain environmental testing services. IT and Quanterra both desire
that IT transfer all of the common stock of Quanterra owned by IT consisting of
1,890 shares of the Class B common stock (the "Class B Common Stock") to
Quanterra, in consideration of the payments to be made as provided herein.

         NOW, THEREFORE, in consideration of the foregoing and the mutual
promises contained herein and intending to be legally bound, the Parties hereby
agree as follows:

         1.       Definitions.  The following terms when used in this
Agreement shall have the-meanings set forth below:

                  "Affiliate" shall mean a corporation, any other business
         entity or a trust, in whatever country organized, which directly or
         indirectly controls, is controlled by or is under common control with a
         Party, where such control is exercised through majority ownership of
         outstanding stock or equity interest, including without limitation the
         ultimate corporate parent of each entity and in the case of IT or ITX,
         any business entity in which IT or ITX owns more than twenty-five
         percent (25%) of the total voting equity, including joint ventures in
         which IT or ITX has the right to receive more than twenty-five percent
         (25%) of the total profits.

                  "Class B Common Stock" shall have the meaning set forth in the
         introduction to this Agreement.

                  "Closing" shall have the meaning set forth in Section 2(e).

                  "Closing Date" shall have the meaning set forth in Section 
         2(e).

                  "Contingent Payment" shall have the meaning set forth in
         Section 2 (b) below.



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                  "Encumbrance" shall mean any pledge, lien, charge,
         encumbrance, security interest, equity, assessment or claim of any kind
         whatsoever.

                  "IT" shall have the meaning set forth in the first paragraph
         to this Agreement.

                  "ITX" shall have the meaning set forth in the first paragraph
         of this Agreement.

                  "Party" shall mean Quanterra, IT or ITX as the context
         requires and if used in the plural, Quanterra, IT and ITX.

                  "Quanterra" shall have the meaning set forth in the first
         paragraph of this Agreement.

                  "Revenues" shall mean the price or compensation (net of all
         applicable discounts and credits) received by Quanterra for
         environmental testing services performed by or on behalf of Quanterra
         or its Affiliates in the ordinary course of business as a result of
         orders or requests made by IT or its Affiliates as set forth on a
         proper customer invoice for such testing services.

                  "1998 Revenues Base" shall have the meaning set forth in
         Section 2 (b) (ii) (1) below.

                  "1999 Revenues" shall have the meaning set forth in Section 2
         (b) (ii) (1) below.

                  "Shareholders' Agreement" shall mean the Amended and Restated
         Shareholders Agreement among Corning Incorporated, IT, ITX and
         Quanterra, dated as of January 1, 1996.

         2. Stock Acquisition and Closing. Subject to the terms and conditions
of this Agreement:

                  (a) At the Closing, for the consideration set forth in
         subsection (b), IT shall transfer and deliver to Quanterra share
         certificates representing 1,890 shares of Class B Common Stock of
         Quanterra constituting all of IT's ownership of or equity in Quanterra
         and all authorized and outstanding shares of capital stock of Quanterra
         held or owned by IT.

                  (b) Upon the terms and subject to the conditions set forth in
         this Agreement, as consideration for the Class B Common Stock to be
         transferred to it, Quanterra shall: (i) pay IT Five Million Seven
         Hundred Fifty Thousand Dollars ($5,750,000) at the Closing by wire
         transfer to an account designated by IT; and (ii) on or before March
         26, 2000, Quanterra shall make an additional payment to IT (the
         "Contingent Payment") (not to



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         exceed, in any event, One Million Three Hundred Fifty Thousand Dollars
         ($1,350,000)); calculated as follows:

                  (1)      $250,000         If the total amount of Revenues 
                                            received by Quanterra for
                                            environmental testing services
                                            commercially supplied by Quanterra
                                            to IT, ITX and their Affiliates and
                                            any successor company to IT in 1999
                                            (the "1999 Revenues") exceed
                                            $8,000,000 or the amount of Revenues
                                            received by Quanterra for
                                            environmental testing commercially
                                            supplied by Quanterra to IT, ITX or
                                            their Affiliates and any successor
                                            company to ITX in 1998, whichever is
                                            higher (the "1998 Revenues Base") by
                                            ten percent (10%) but less than
                                            twenty-five percent (25%); or

                  (2)      $600,000         If the 1999 Revenues exceed the 1998
                                            Revenues Base by twenty-five percent
                                            (25%) or more but less than forty
                                            percent (40%); or

                  (3)      $900,000         If the 1999 Revenues exceed the 1998
                                            Revenues Base by forty percent (40%)
                                            but less than fifty percent (50%); 
                                            or

                  (4)      $1,350,000       If the 1999 Revenues exceed the 1998
                                            Revenues Base by more than fifty
                                            percent (50%).

         All services provided by Quanterra to IT or ITX and ordered by IT, ITX
         or their Affiliates from Quanterra in 1998 will be consistent with the
         levels achieved during the first half of 1998 and Quanterra, IT and ITX
         will at all times act in good faith and consistent with their
         respective contractual commitments in purchasing from Quanterra and
         supplying to IT and ITX environmental testing services in 1998 and
         1999.

                  (d) Quanterra and its Affiliates, as may be appropriate, shall
         keep records of all 1998 Revenues Base and 1999 Revenues on which the
         Contingent Payment is calculated in a suitable book or books provided
         for this purpose in sufficient detail to enable the Contingent Payment
         payable under this Agreement to be accurately determined. Within ninety
         (90) days after the end of each calendar quarter from the date of this
         Agreement up to and including December 31, 1999, Quanterra shall
         deliver to ITX written reports of all transactions used to calculate
         the 1998 Revenues Base and the, 1999 Revenues, and with the last report
         the manner and amount of the Contingent Payment calculation. If ITX
         materially disagrees with any report or the calculation of the
         Contingent Payment, ITX and Quanterra shall meet within thirty (30)
         days to resolve any dispute amicably. If the Parties do not resolve any
         such dispute at this meeting, then Price Waterhouse & Co. shall be
         hired to audit the records of Quanterra and verify its reports or if it
         cannot, to calculate the 1999 Revenues and 1998 Revenues Base and
         report the result to the Parties



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         in writing no later than sixty (60) days from the date of the meeting
         described above. ITX and Quanterra shall each pay fifty percent (50%)
         of total costs and fees of Price Waterhouse & Co. to perform this
         service.

                  (e) Closing. The closing of the transactions contemplated by
         this Agreement (the "Closing") shall take place at the offices of
         Quanterra, 5251 DTC Parkway, Suite 415, Englewood, Colorado, or such
         other place as may be mutually agreed upon, at nine thirty o'clock a.m.
         on June 26, 1998, or such other date as may be mutually agreed upon
         (the "Closing Date').

                  (f) All of the obligations of ITX, IT and their Affiliates
         under this Agreement shall be binding upon and apply to any successor
         or surviving corporation of ITX or IT whether or not resulting from any
         merger or combination with any other entity and whether or not IT is
         the surviving entity for a period ending on June 26, 2001.

         3. Representation and Warranties by IT and ITX. IT and ITX represent
and warrant to Quanterra that:

                  (a) Corporate Organization and Authority. IT and ITX are
         corporations duly organized, validly existing and in good corporate
         standing under the laws of California and Delaware respectively; that
         each has the full corporate power and authority to execute and deliver
         this Agreement and the other agreements and instruments executed or to
         be executed and delivered by them in connection herewith and to
         consummate the transactions contemplated hereby and thereby.

                  (b) Corporate Proceedings; Validity; Enforceability. All
         corporate acts and other proceedings required to be taken by or on the
         part of IT and ITX to authorize them to carry out this Agreement and
         transfer the Class B Common Stock to Quanterra and the other agreements
         and instruments executed or to be executed and delivered by them in
         connection herewith and the transactions contemplated hereby and
         thereby have been duly and properly taken prior to the Closing Date.
         This Agreement has been duly executed and delivered by IT and ITX and
         constitutes, and each such other agreement and instrument constitutes,
         or when duly executed and delivered, shall constitute, the legal, valid
         and binding obligation of IT and ITX, enforceable in accordance with
         its terms.

                  (c) No Violation. The execution and delivery by IT and ITX of
         this Agreement and the other agreements and instruments executed or to
         be executed and delivered by it in connection herewith and their
         consummation of the transactions contemplated hereby and thereby shall
         not (i) violate any provision of law, (ii) violate the provisions of
         any order, judgment or decree of any court or governmental agency or
         authority applicable to IT or ITX or its property or business or
         violate the Certificate of Incorporation or ByLaws of Quanterra or
         (iii) result in a breach of or constitute a default (or an event that
         with the giving of notice or lapse of time or both would become a
         default) under, or result



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         in the creation of an Encumbrance on the Class B Common Stock pursuant
         to any indenture, mortgage, lease, agreement or other instrument to
         which IT or ITX is a party or by which either is bound.

                  (d) Approvals. No approval, consent, waiver or other order or
         action of or filing or registration with any court or other
         governmental authority is required for the execution and delivery by IT
         and ITX of this Agreement and the other agreements and instruments
         executed or to be executed and delivered by IT and ITX in connection
         herewith and the consummation by IT and ITX of the transactions
         contemplated hereby and thereby, including without limitation the
         transfer of the Class B Common Stock.

                  (e) Class B Common Stock. The Class B Common Stock constitutes
         all of the stock in Quanterra owned or controlled by IT, ITX or their
         Affiliates and is all of the equity or other interest or right IT, ITX
         or their Affiliates have in Quanterra and is free and clear of any
         Encumbrance.

                  (f) Finders; Brokers. IT and ITX are not parties to any
         understanding with, or in any way obligated to, any finder or broker
         for any commissions, fees, or expenses in connection with the
         origination, negotiation, execution or performance of this Agreement.

         4. Representations by Quanterra. Quanterra represents and warrants to
IT and ITX that:

                  (a) Corporate Existence and Power. Quanterra is a corporation
         duly organized, validly existing and in good standing under the laws of
         Delaware; it has the full corporate power and authority to execute and
         deliver of this Agreement and the other agreements and instruments
         executed or to be executed and delivered by it in connection herewith
         and it consummate the transactions contemplated hereby and thereby.

                  (b) Corporate Proceedings; Validity; Enforceability. All
         corporate acts and other proceedings required to be taken by or on the
         part of Quanterra to authorize it to carry out this Agreement and the
         other agreements and instruments executed or to be executed and
         delivered by it in connection herewith and the transactions
         contemplated hereby and thereby have been duly and properly taken prior
         to the Closing Date. This Agreement has been duly executed and
         delivered by Quanterra and constitutes, and each such other agreement
         and instrument constitutes, or when duly executed and delivered, shall
         constitute, the legal, valid and binding obligation of Quanterra,
         enforceable in accordance with its terms.

                  (c) Approvals. No approval, consent, waiver or other order or
         action of or filing or registration with any court or other
         governmental authority is required for the execution and delivery by
         Quanterra of this Agreement and the other agreements and



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         instruments to be executed and delivered by Quanterra pursuant hereto
         and the consummation by Quanterra of the transactions contemplated
         hereby and thereby.

                  (d) Finders; Brokers. Quanterra is not a party to any
         understanding with any finder or broker which would subject Quanterra
         to liability for any commissions, fees or expenses in connection with
         the origination, negotiation, execution or performance of this
         Agreement.

                  (e) No Violation. The execution and delivery by Quanterra of
         this Agreement and the other agreements and instruments executed or to
         be executed and delivered by it in connection herewith and its
         consummation of the transactions contemplated hereby and thereby shall
         not (i) violate any provision of law, (ii) violate the Provisions of
         any order, judgment or decree of any court or other governmental agency
         or authority applicable to Quanterra or its property or business or
         violate the Articles of Incorporation, as amended and restated, of
         Quanterra or (iii) result in a breach of or constitute a default (or an
         event that with the giving of notice or lapse of time or both would
         become a default) under any indenture, mortgage, lease, agreement or
         other instrument to which Quanterra is a party or by which it is bound.

         5.       Additional Covenants.

                  (a) Termination of the Shareholders' Agreement. Quanterra, IT
         and ITX hereby agree that effective on the Closing Date, the
         Shareholders Agreement shall be terminated and each of Quanterra, IT
         and ITX hereby release each other and Corning Incorporated from any
         claim whatsoever arising out of or related to that Agreement and any
         other instrument or agreement executed in connection therewith.

                  (b) Except as expressly set forth in this Agreement, nothing
         contained in this Agreement shall be deemed to amend the Asset Transfer
         Agreement dated as of May 2, 1994 among MetPath, ITX and IT, as amended
         as of June 25, 1994 (the "'Asset Transfer Agreement"), or the other
         documents delivered at the closing thereunder, or to relieve any Party
         thereto of any obligation set forth in the Asset Transfer Agreement or
         such other documents, including without limitation, Sections 12 (b) and
         12 (c) of the Asset Transfer Agreement.

                  (c) For a period of three (3) years from the date of this
         Agreement, IT, ITX and any successor to IT and ITX shall use all
         reasonable efforts consistent with past practices to cause their
         Affiliates and their respective customers, to utilize the services of
         laboratories owned and operated by Quanterra, including, whenever
         possible, by referring clients and others to Quanterra's laboratories
         and by providing for the use of Quanterra's laboratories in their
         contracts with their clients. In furtherance of the foregoing, IT and
         ITX shall send to its Affiliates and the headquarters of its major
         operations a letter in



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         substantially the form of Exhibit A hereto within fifteen (15) days of
         the date of this Agreement.

                  (d) During the three (3) year period described in subsection
         (c) above, IT and ITX shall, within thirty (30) days of the end of each
         calendar quarter, send to Quanterra a written report setting forth the
         extent of its Affiliates' purchase of environmental services of the
         type supplied by Quanterra and the percentage of such services which
         IT, ITX and their Affiliates have purchased from Quanterra.

                  (e) During the three (3) year period described in subsection
         (c) Above, Quanterra shall use all reasonable efforts to maintain
         sufficient capacity to process all samples originating from IT, ITX or
         their Affiliates and their customers, and to actually process such
         samples on bases at least as favorable as those Quanterra offers to
         similar clients for similar testing at similar volumes. In furtherance
         of the foregoing, Quanterra agrees to use all reasonable efforts to
         offer to IT, ITX and their Affiliates and their clients, prices,
         turnaround times, and other terms and conditions at least as favorable
         as those offered to similar clients of Quanterra which purchase similar
         services in similar volumes. Quanterra also agrees to maintain such
         quality assurance/quality control and similar programs as ITX may
         reasonably request in its efforts to utilize and refer business to
         Quanterra laboratories.

                  (f) IT and ITX shall cause their Affiliates to pay Quanterra
         no later than sixty (60) days after the date of an invoice, all
         environmental testing services ordered by and on behalf of IT, ITX or
         their Affiliates and performed by Quanterra. Nothing contained in this
         Section 5(f) shall prejudice any right IT or ITX may have not to pay
         for services that have not been satisfactorily performed.

         6.       Conditions.

                  (a) Obligations of IT. The obligations of IT to close and to
         transfer the Class B Common Stock shall be subject to the following:

                           (1) Consideration. IT shall have received the payment
                  required to be made in accordance with Section 2 (a).

                           (2) Representations and Warranties True at Closing.
                  The representations and warranties made by Quanterra in this
                  Agreement and in any certificate or document delivered
                  pursuant to the provisions hereof shall be true in all
                  material respects at and as of the Closing Date as though such
                  representations and warranties were made at and as of such
                  time.



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                           (3) Performance. Quanterra shall have performed and
                  complied in all material respects with all agreements and
                  conditions required by this Agreement to be performed complied
                  with by it prior to or at the Closing Date.

                           (4) Legal Matters. All legal matters incident to the
                  consummation of the transactions contemplated hereby shall be
                  satisfactory to counsel for IT.

                           (5) Certificate of Officer, IT shall have received a
                  certificate of an officer for Quanterra, dated the Closing
                  Date and addressed to IT, to the effect that (a) Quanterra has
                  been duly organized and is validly existing and in good
                  standing under the laws of California and has the corporate
                  power to execute, deliver and carry out the terms and
                  provisions of this Agreement; (b) this Agreement has been
                  executed and delivered by Quanterra and is the legal, valid
                  and binding obligation of Quanterra enforceable in accordance
                  with its terms.

                           (6) Action or Proceeding. No suit, action or
                  proceeding, or governmental investigation or inquiry against
                  or concerning,. directly or indirectly, IT or Quanterra, or
                  any of the properties of any of the foregoing shall have been
                  instituted or threatened, nor shall any basis therefor have
                  arisen that might result in any order or judgment of any court
                  or other governmental agency or authority which in the opinion
                  of IT is of such significance or materiality and of such a
                  nature as to render it inadvisable, to consummate the
                  transactions contemplated by this Agreement.

                           (7) Consent to Termination. Corning Incorporated has
                  executed a consent to the termination of the Shareholders
                  Agreement substantially in the form of Exhibit B hereto.

                  (b) Obligations of Quanterra. The obligations of Quanterra to
         close and to acquire the Class B Common Stock shall be subject to the
         following:

                           (1) Receipt of Class B Common Stock. Quanterra shall
                  have received from IT certificates evidencing an aggregate of
                  1,890 shares of Class B Common Stock.

                           (2) Representations and Warranties at Closing. The
                  representations and warranties made by IT and ITX in this
                  Agreement and in any certificate or document delivered
                  pursuant to the provisions hereof shall be true in all
                  material respects at and as of the Closing Date as though such
                  representations and warranties were made at and as of such
                  time.



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                           (3) Performance. IT and ITX shall have performed and
                  complied in all material respects with all agreements and
                  conditions required by this Agreement to be performed or
                  complied with by it prior to or at the Closing Date.

                           (4) Legal Matters. All legal matters incident to the
                  consummation of the transactions contemplated hereby shall be
                  satisfactory to counsel for Quanterra.

                           (5) Certificate of Officer. Quanterra shall have
                  received a certificate of an officer for IT and an officer of
                  ITX, dated the Closing Date and addressed to Quanterra, to the
                  effect that (a) IT and ITX have been duly organized and are
                  validly existing and in good standing under the laws of
                  California and Delaware respectively and that each has the
                  corporate power to execute, deliver and carry out the terms
                  and provisions of this Agreement; (b) this Agreement has been
                  executed and delivered by IT and ITX and is the legal, valid
                  and binding obligation of IT and ITX enforceable in accordance
                  with its terms.

                           (6) Action or Proceeding. No suit, action or
                  proceeding, or governmental investigation or inquiry against
                  or concerning, directly or indirectly, Quanterra, IT or ITX,
                  or any of the properties of any of the foregoing shall have
                  been instituted or threatened, nor shall any basis therefor
                  have arisen that might result in any order or judgment of any
                  court or other governmental agency or authority which in the
                  opinion of Quanterra is of such significance or materiality
                  and of such a nature as to render it inadvisable, to
                  consummate the transactions contemplated by this Agreement.

         7. Notices. All notices and communications hereunder given by any Party
to any other Party shall be in writing (including by telex, confirmed in
writing) and shall be deemed to have been duly given when received if delivered
in person or by mail, first-class, postage and certified mail prepaid, and when
sent, if sent by telex, answer back received, addressed to the respective
Parties hereto as follows:

                  If to Quanterra:  Quanterra Incorporated
                                    5251 DTC Parkway, Suite 415
                                    Englewood, CO 80111

                                    Attention: President

                  If to IT:         IT Corporation
                                    2790 Mosside Boulevard
                                    Monroeville, PA 15146

                                    Attention:



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                  If to ITX:        International Technology Corporation
                                    2790 Mosside Boulevard
                                    Monroeville, PA 15146

                                    Attention:

or to such other address as to either Party as such Party shall designate by
written notice to the other Party hereto.

         8. Further Assurances. Upon request from time to time, each Party shall
execute and deliver all documents, take all rightful oaths, and do all other
acts that may be reasonably necessary or desirable, in the opinion of counsel
for the other Party, to perfect the title of Quanterra, to the Class B Common
Stock to be acquired under this Agreement, or to aid in the presentation,
defense or other litigation of any rights arising from such Class B Common Stock
or the resolution of any claims arising out of the operations of Quanterra
during the period in which IT was a shareholder of Quanterra or otherwise to
effect the transactions contemplated by this Agreement.

         9. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York.

         10. Nonassignability. This Agreement shall not be assigned by either
Party hereto without the express prior written consents of the other Parties
hereto, provided however, Quanterra may assign it interest in this Agreement on
a one time basis in connection with sale of all or substantially all of its
business or assets. Any attempted assignment in breach of this section, and
without such consents as are required hereby, shall be null and void.

         11. Captions; Exhibits. The captions appearing herein are f or the
convenience of the Parties only, and shall not be construed to affect the
meaning of the provisions of this Agreement. All Exhibits referred to herein are
annexed hereto and hereby made a part of this Agreement, and any document or
matter referenced in any Exhibit shall be deemed referred to in every Exhibit.

         12. Arbitration. All disputes or differences arising out of or related
in any way to this Agreement shall be submitted to the decision of three (3)
arbitrators, one to be chosen by each party, and the third to be chosen by the,
two previously selected arbitrators. If either of the parties fails to appoint
an arbitrator within one (1) month after receipt of a demand to arbitrate, such
arbitrator shall at the request of either party be appointed by application to
the courts of New York having competent jurisdiction therefor.

         The arbitration proceedings shall take place in New York. The applicant
shall submit its case within one (1) month after the appointment of the
arbitration panel, and the respondent shall



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<PAGE>   11



submit his reply within one (1) month after receipt of a claim. The arbitrators
shall apply the rules of evidence and law applicable in courts sitting in New
York.

         The arbitration panel shall be empowered to award provisional (i.e.,
injunctive) relief upon proper application, but a party shall be entitled,
pending the appointment of all such arbitrators and the convening of such
arbitration, to seek such relief from any court otherwise having competent
jurisdiction of such matter.

         The arbitration panel shall render a written, reasoned decision on each
issue before it, in which decision it shall also state bow each arbitrator
voted. Any decision by the arbitration panel shall be binding upon the parties
and may be entered as a final judgment in any court having jurisdiction. The
cost of any arbitration proceeding shall be borne by the parties as the
arbitrator shall determine if the parties have not otherwise agreed.

         13. Entire Agreement. This Agreement including the exhibits attached
hereto contains the entire understanding between the Parties with regard to the
subject matter hereof and shall be binding and enforceable by the Parties and
their respective successors. Except as otherwise provided herein, neither this
Agreement nor any provisions hereunder may be amended, modified, waived or
discharged unless such amendment, modification, waiver or discharge is agreed to
in a writing, duly subscribed and acknowledged with the same formality as this
Agreement, and signed by each of Quanterra, IT and ITX. Any waiver of a right,
term or provision hereunder by a Party hereto shall not be deemed a continuing
waiver unless so specified and shall not prevent or stop a Party hereto from
thereafter enforcing such right, term or provision, and the failure of a Party
hereto to insist in one or more instances upon strict performance by another
Party hereto, of any of the terms and provisions of this Agreement shall not be
construed as a waiver or relinquishment for the future of any such right, terms
or provision, but the same shall continue in full force and effect.

         14. Severability. If any provision contained in this Agreement shall to
any extent be held invalid or unenforceable, such invalidity or unenforceability
shall not affect the validity or enforceability of any other provision of this
Agreement which shall remain in full force and effect. Any provision contained
in this Agreement which is held to be invalid or unenforceable under applicable
law shall be, if possible, modified or altered to conform to such applicable
law, or if not possible, shall be deemed to be omitted herefrom.

         15. Execution in Counterparts. This Agreement may be executed in two or
more counterparts, each of which shall be deemed an original, and it shall not
be deemed necessary in making proof of this Agreement to produce or account for
more than one counterpart signed by the Party to be charged thereby.

         16. Expenses. Each Party to this Agreement shall pay its own expenses
incurred in connection with this Agreement and the transactions contemplated
hereunder.



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<PAGE>   12


         17. Interpretation. Neither the captions of the various sections of
this Agreement which are for convenience or reference only, nor the identity of
the Party which drafted this Agreement shall be accorded weight in the
interpretation of this Agreement.

         18. Specific Enforcement. Notwithstanding any other provision of this
Agreement, it is understood and agreed that damages and any other remedies at
law may be inadequate in the case of any breach by any Party hereto of any of
the provisions hereof, and each Party hereto agrees that the other Parties shall
be entitled to equitable relief and the remedy of specific performance with
respect to any breach or attempted breach of any of the provisions hereof.

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

                             QUANTERRA INCORPORATED


                             By: /s/ BRAD S. FIGLEY
                                 -----------------------------------------------
                                     Brad S. Figley
                                     Senior Vice President



                             INTERNATIONAL TECHNOLOGY CORPORATION


                             By: /s/ ANTHONY J. DELUCA
                                 -----------------------------------------------
                                     Anthony J. DeLuca, President and
                                     Chief Executive Officer



                             IT CORPORATION


                             By: /s/ ANTHONY J. DELUCA
                                 -----------------------------------------------
                                     Anthony J. DeLuca, President



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<PAGE>   13

                           CONSENT TO THE TERMINATION
                           OF THE AMENDED AND RESTATED
                          SHAREHOLDERS AGREEMENT AMONG
                       CORNING INCORPORATED, INTERNATIONAL
                     TECHNOLOGY CORPORATION, IT CORPORATION
                           AND QUANTERRA INCORPORATED






         In connection with the Amended and Restated Shareholders Agreement
dated as of January 1, 1996 among Corning Incorporated ("Corning"),
International Technology Corporation ("ITX"), IT Corporation ("IT") and
Quanterra Incorporated ("Quanterra") (the "Shareholders Agreement"), Corning
hereby agrees to the termination of such Agreement and releases each and every
party to such Shareholders Agreement from any claim whatsoever arising out of or
related to the Shareholders Agreement.


                                   CORNING INCORPORATED

                                   By:
                                      ------------------------------------------


Dated:   June 26, 1998






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