1
                                                                    EXHIBIT 2.15


                 AMENDED AND RESTATED SHARE REPURCHASE AGREEMENT


      AMENDED AND RESTATED SHARE REPURCHASE AGREEMENT (this "Agreement"), dated
as of February 11, 1998, among OHM Corporation, an Ohio corporation (the
"Company"), Waste Management, Inc., a Delaware corporation ("WMX"), Rust
International Inc., a Delaware corporation ("Rust"), Rust Remedial Services
Holding Company Inc., a Delaware corporation (the "Shareholder"), and
International Technology Corporation, a Delaware corporation ("Parent").

      WHEREAS, certain of the parties are party to the Share Repurchase
Agreement, dated as of January 15, 1998, among OHM Corporation, Waste
Management, Inc., Rust International Inc., and International Technology
Corporation (the "Original Agreement"), and certain of the parties to this
Agreement are also parties to the Standstill and Non-Competition Agreement,
dated as of May 30, 1995, among the Company, WMX and Rust (the "Standstill
Agreement"); and

      WHEREAS, concurrently with the execution of the Original Agreement, the
Company, Parent and IT-Ohio, Inc., an Ohio corporation ("Merger Sub"), entered
into an Agreement and Plan of Merger, dated as of January 15, 1998 (as it may be
amended from time to time, the "Merger Agreement"), which provides that Merger
Sub will make a tender offer (the "Offer") for 13,933,000 shares of Common
Stock, par value $0.10 per share, of the Company ("Shares") and that, subsequent
to the consummation of the Offer, Merger Sub will merge with and into the
Company (the "Merger" and, collectively with the Offer and the other
transactions contemplated by the Merger Agreement, the "Merger Transactions");
and

      WHEREAS, the Shareholder is the record holder of an aggregate of 9,668,000
Shares (the "Shareholder Shares"); and

      WHEREAS, Parent, the Company, WMX and the Shareholder wish, as a part of
the Merger Transactions, to provide for the repurchase by the Company from the
Shareholder, concurrently with the payment to BankBoston, N.A., as Depositary
for the Offer on behalf of holders of Shares tendering into the Offer, of the
aggregate purchase price for all Shares purchased in the Offer (the "Payment
Time"), of 5,235,381 Shareholder Shares (the "Repurchased


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Shares"), in a manner that will increase the aggregate number of Shares acquired
for cash in the Merger Transactions and make it possible for the Merger
Consideration (as defined in the Merger Agreement) to consist solely of shares
of Parent Common Stock (as defined in the Merger Agreement); and

      WHEREAS, the parties intend for WMX and the Shareholder, considered
together, not to receive any greater consideration per Share in the Merger
Transactions than the other holders of Shares, and that for Shareholder not to
receive any greater amount of cash consideration per Share in the Merger
Transactions than the other holders of Shares; and

      WHEREAS, in order to facilitate consummation of the Merger Transactions,
WMX and the Shareholder wish to agree (i) to vote or cause to be voted the
Shareholder Shares and any other shares of capital stock of the Company held by
either of them so as to facilitate consummation of the Merger Transactions, (ii)
except as provided in this Agreement, not to transfer or otherwise dispose of or
permit to be transferred or otherwise disposed of any of the Shareholder Shares,
or any other shares of capital stock of the Company, acquired by either of them
hereafter and prior to the Effective Time (as defined in the Merger Agreement),
(iii) to deliver to Parent an irrevocable proxy to vote the Shareholder Shares
and any other shares of capital stock of the Company acquired by the Shareholder
or WMX hereafter and prior to the Effective Time, and (iv) to amend or
terminate, as the case may be, certain agreements to which certain of the
parties hereto are parties, and (v) to make certain other agreements, all as
provided for herein.

      NOW, THEREFORE, for good and valuable consideration, the receipt,
sufficiency and adequacy of which is hereby acknowledged, the parties hereto
hereby amend and restate the Original Agreement, ab initio, as follows:


                                    ARTICLE I

                   Definitions; Representations and Warranties

      1.1   Definitions. Terms used herein but not defined herein shall have the
respective meanings ascribed to such terms in the Merger Agreement.


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      1.2   Representations of WMX and the Shareholder. WMX and the Shareholder
jointly and severally represent and warrant to the Company that (a) the
Shareholder owns beneficially and of record (as such term is defined in the
Securities Exchange Act of 1934, as amended (the "1934 Act")) 9,668,000 Shares
free and clear of all liens, claims, charges, security interests or other
encumbrances (each, a "Lien") and, except for this Agreement and the warrants to
purchase Shares (the "Warrants") issued pursuant to the Warrant Agreement, dated
as of May 30, 1995, among the Company and WMX (the "Warrant Agreement"), there
are no options, warrants or other rights, agreements, arrangements or
commitments of any character to which WMX or the Shareholder is a party relating
to the pledge or disposition of any shares of capital stock of the Company and,
except for the Standstill Agreement and this Agreement, there are no voting
trusts or voting agreements to which WMX or the Shareholder is a party with
respect to any shares of capital stock of the Company; (b) neither WMX nor the
Shareholder beneficially owns any shares of capital stock of the Company other
than the Shareholder Shares, in the case of the Shareholder, and the Warrants,
in the case of WMX, and, except for the Warrants held by WMX, neither has any
options, warrants or other rights to acquire any additional shares of capital
stock of the Company or any security exercisable for or convertible into shares
of capital stock of the Company; (c) WMX and the Shareholder have full power and
authority to enter into, execute and deliver this Agreement and to perform fully
their respective obligations under this Agreement; and (d) this Agreement has
been duly executed and delivered by each of WMX, the Shareholder and Rust,
constitutes the legal, valid and binding obligation of WMX, the Shareholder and
Rust and is enforceable against each of them in accordance with its terms. The
foregoing representations shall survive consummation of the Merger Transactions
and the other transactions contemplated by this Agreement.

      1.3   Representations of the Company. The Company represents and warrants
to WMX and the Shareholder that (a) the Company has full power and authority to
enter into, execute and deliver this Agreement and to perform fully its
obligations under this Agreement, (b) this Agreement has been duly executed and
delivered by the Company, constitutes the legal, valid and binding obligation of
the Company and is enforceable against it in accordance with its terms, and (c)
the Company has obtained all consents, approvals,


                                      -3-
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permits and authorizations required to be obtained by the Company pursuant to
any law, regulation, contract, agreement or instrument in connection with the
execution and delivery of this Agreement. The foregoing representations shall
survive consummation of the Merger Transactions and the other transactions
contemplated by this Agreement.


                                   ARTICLE II

                          The Repurchase and the Offer

      2.1   Repurchase of Shares. (a) Subject to the terms and conditions of
this Agreement, including the conditions set forth in Section 2.3, the Company
agrees to purchase from the Shareholder, and the Shareholder agrees to sell to
the Company (such purchase and sale transaction, the "Repurchase"), the
Repurchased Shares, free and clear of any Liens at a purchase price of $11.50
per Repurchased Share, or such greater price per Repurchased Share as may be
paid in the Offer (the "Repurchase Price").

            (b)   If for any reason the Company has not repurchased the
Repurchased Shares immediately prior to the Effective Time (as defined in the
Merger Agreement), the Company shall take such action as may be necessary at
such time to purchase the Repurchased Shares at the Repurchase Price for cash at
such time, so that the Repurchased Shares shall have been acquired by the
Company, Parent or Merger Sub prior to the Effective Time.

      2.2   Repurchase Closing. (a) The delivery of the Repurchased Shares (the
"Repurchase Closing") shall take place at the offices of Sullivan & Cromwell,
125 Broad Street, New York, New York at the Payment Time.

            (b)   At the Repurchase Closing:

                  (i)   The Shareholder shall deliver to the Company
      certificates representing the Repurchased Shares, duly endorsed and in
      form for transfer to the Company; and

                  (ii)  The Company shall pay to the Shareholder, by wire
      transfer, to an account designated by the Shareholder no fewer than two
      business days prior to the Repurchase Closing, immediately available


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      funds equivalent to the Repurchase Price multiplied by the number of
      Repurchased Shares.

      2.3   Conditions to the Repurchase. (a) The respective obligations of the
Company and the Shareholder to consummate the Repurchase are subject to the
fulfillment of each of the following conditions, any or all of which may be
waived in whole or in part by the Company or the Shareholder, as the case may
be, to the extent permitted by applicable law:

                  (i)   Concurrently with the Repurchase Closing, Merger Sub
      shall have paid for Shares pursuant to the Offer.

                  (ii)  No United States or state court or other Governmental
      Entity (as defined in the Merger Agreement) of competent jurisdiction
      shall have enacted, issued, promulgated, enforced or entered any statute,
      rule, regulation, judgment, decree, injunction or other order (whether
      temporary, preliminary or permanent) which is in effect and prohibits
      consummation of the transactions contemplated by the Merger Agreement or
      this Agreement.

            (b)   The obligation of the Company to consummate the Repurchase is
subject to the condition that the representations and warranties of WMX and the
Shareholder contained in Section 1.2 are true and accurate in all material
respects as of the date hereof and as of the Repurchase Closing, provided,
however, that the foregoing condition may be waived in whole or in part by the
Company.

            (c)   The obligation of WMX and the Shareholder to consummate the
Repurchase is subject to the condition that the representations and warranties
of the Company contained in Section 1.3 are true and accurate in all material
respects as of the date hereof and as of the Repurchase Closing, provided,
however, that the foregoing condition may be waived in whole or in part by WMX
by the Shareholder.

      2.4   The Tender Offer. WMX and the Shareholder agree that they will not,
in the aggregate, tender more than 2,142,141 Shares into the Offer.


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                                   ARTICLE III

                                   The Merger

      3.1   Agreement to Vote Shares. In addition to and notwithstanding the
provisions of Section 1.2 of the Standstill Agreement, WMX and the Shareholder
agree that during the term of this Agreement they consent to and approve the
voting of the Shareholder Shares and any New Shares (as defined in Section 4.2),
(a) in favor of adoption of the Merger Agreement and in favor of consummation of
the Merger Transactions at every meeting of the shareholders of the Company at
which such matters are considered and at every adjournment thereof or in
connection with any written consent of the shareholders of the Company, (b) in
favor of the election to the Company's Board of Directors of such number of
Parent Representatives as Parent is permitted to cause to be elected to the
Company's Board of Directors pursuant to Section 1.4 of the Merger Agreement,
(c) against any action or agreement that would compete with, impede, interfere
with or attempt to discourage the Merger Transactions, or inhibit the timely
consummation of the Merger Transactions, (d) against any action or agreement
that would result in a breach in any material respect of any covenant,
representation or warranty or any other obligation of the Company under the
Merger Agreement and (e) against any merger, consolidation, business
combination, reorganization, recapitalization, liquidation or sale or transfer
of any material assets of the Company or its subsidiaries, except for the Merger
Transactions. The Shareholder agrees to deliver to Parent upon request a proxy
substantially in the form attached hereto as Exhibit A, which proxy shall be
irrevocable during the term of this Agreement to the fullest extent permitted
under Ohio law.

      3.2   No Voting Trusts. WMX and the Shareholder agree that they will not,
nor will they permit any entity under their control to, deposit any of the
Shareholder Shares or any New Shares held by them or any entity under their
control in a voting trust or subject any of the Shareholder Shares or any New
Shares held by them or any entity under their control to any arrangement with
respect to the voting of the Shareholder Shares that could result in a
shareholder's vote or action by consent of the shareholders of the Company in
opposition to or in competition with the consummation of the Merger
Transactions.


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      3.3   No Proxy Solicitations. WMX and the Shareholder agree that they will
not, nor will they permit any entity under their respective control to, (a)
solicit proxies or become a "participant" in a "solicitation" (as such terms are
defined in Regulation 14A under the 1934 Act) in opposition to or in competition
with the consummation of the Merger Transactions or otherwise encourage or
assist any party in taking or planning any action which would compete with,
impede, interfere with or attempt to discourage the Merger Transactions or
inhibit the timely consummation of the Merger Transactions, (b) directly or
indirectly encourage, initiate or cooperate in a shareholders' vote or action by
consent of the Company's shareholders in opposition to or in competition with
the consummation of the Merger Transactions, or (c) become a member of a "group"
(as such term is used in Section 13(d) of the 1934 Act) with respect to any
voting securities of the Company for the purpose of opposing or competing with
the consummation of the Merger Transactions.

      3.4   Waiver of Dissenters' Rights. The Shareholder hereby unconditionally
and irrevocably waives its rights pursuant to Sections 1701.84 et seq. of the
Ohio General Corporation Law to exercise appraisal rights or dissenters' rights
with respect to the Offer, the Merger, or the other transactions contemplated by
the Merger Agreement.


                                   ARTICLE IV

                                Other Agreements

      4.1   No Transfer or Encumbrance. In addition to and notwithstanding the
provisions of Section 1.8 of the Standstill Agreement, WMX and the Shareholder
agree not to transfer, sell, offer, exchange, pledge or otherwise dispose of or
encumber any of the Warrants, Shareholder Shares or New Shares on or after the
date hereof and during the term of this Agreement, except for tenders in
accordance with Section 2.4, unless the transferee agrees in writing in form
satisfactory to the Company and Parent to be bound by the terms of this
Agreement.

      4.2   No Additional Purchases or Acquisitions. In addition to and
notwithstanding the provisions of Sections 1.1 and 2.4 of the Standstill
Agreement, WMX and the Shareholder agree that they will not purchase or
otherwise


                                      -7-
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acquire beneficial ownership of any Shares or any other capital stock of the
Company after the execution of this Agreement ("New Shares"), nor will WMX or
the Shareholder voluntarily acquire the right to vote or share in the voting of
any Shares or any other capital stock of the Company other than the Shareholder
Shares, unless (in either case) WMX or the Shareholder, as the case may be,
agrees to deliver to the Board of Directors of the Company immediately after
such purchase or acquisition an irrevocable proxy in the form attached hereto as
Exhibit A with respect to such New Shares. WMX and the Shareholder also agree
that any New Shares acquired or purchased by them shall be subject to the terms
of this Agreement to the same extent as if they constituted Shareholder Shares.

      4.3   First Amendment to Standstill Agreement. The Standstill Agreement is
hereby amended ab initio, as of the execution of this Agreement, to amend
Section 1.4 thereof by adding the following clause to the end of such Section:

      ", except the Amended and Restated Share Repurchase Agreement, dated
      February 11, 1998, among OHM Corporation, Waste Management, Inc., Rust
      International Inc., Rust Remedial Services Holding Company Inc. and
      International Technology Corporation."

      4.4   Second Amendment to Standstill Agreement. The Standstill Agreement
is hereby further amended ab initio, as of the occurrence of the Repurchase
Closing, to delete therefrom Sections 2.1 through 2.7 thereof in their entirety.

      4.5   Third Amendment to Standstill Agreement. The Standstill Agreement is
hereby further amended ab initio, as of the Repurchase Closing, to delete
therefrom Sections 3.1, 3.2 and 3.3 thereof in their entirety.

      4.6   Release from Intercreditor Agreement. WMX and the Shareholder hereby
consent to the payment by the Company of a pro rata taxable distribution (the
"NSC Distribution") to holders of record of the Shares of all of the shares of
common stock, par value $0.01 per share, of NSC Corporation held by the Company
(the "NSC Shares") and waive their rights to reimbursement pursuant to the
Reimbursement Agreement, dated as of May 31, 1995, among the Company,
Remediation and WMX, and the Intercreditor


                                      -8-
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Agreement, dated as of May 31, 1995, among WMX, the Administrative Agent and the
Issuing and Paying Agent, and hereby release the NSC Shares from any security
interest (pursuant to pledge agreements or otherwise) which WMX may have with
respect to such NSC Shares. WMX agrees to execute any documents reasonably
necessary to give effect to the provisions of this Section, promptly upon
request therefor made by the Company.

      4.7   Termination of the Guaranty Agreement. The parties hereby agree that
the Guaranty Agreement, dated as of May 30, 1995, between the Company and WMX,
shall be terminated effective as of the Common Termination Date.

      4.8   Cancellation of The Warrants.

            (a)   The parties hereby agree that the Warrant Agreement shall be
terminated and the Warrants shall be canceled effective as of the date on which
the Guaranty, made as of May 31, 1995, by WMX in favor of the Banks listed
therein (the "Guaranty"), terminates in accordance with Section 10(a) thereof
(such date, the "Common Termination Date"), without the payment of any separate
consideration therefor. The parties hereby agree to use their reasonable best
efforts to cause the events specified in Section 10(a) of the Guaranty to occur
prior to the second business day subsequent to the Effective Time.

            (b)   WMX agrees not to exercise its rights pursuant to Sections 3.1
or 3.2 of the Warrant Agreement prior to the earlier to occur of (i) the second
business day subsequent to the Effective Time, and (ii) the termination of the
Merger Agreement in accordance with its terms.

            (c)   WMX agrees not to exercise its rights pursuant to Section 2.2
of the Warrant Agreement with respect to the Merger Transactions prior to the
second business day subsequent to the Effective Time.

            (d)   WMX hereby waives its rights under Sections 2.1 through 2.7 of
the Warrant Agreement with respect to the NSC Distribution.


                                      -9-
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                                    ARTICLE V

                                  Miscellaneous

      5.1   Specific Performance. Each party hereto acknowledges that it will be
impossible to measure in money the damage to the other party if a party hereto
fails to comply with any of the obligations imposed by this Agreement, that
every such obligation is material and that, in the event of any such failure,
the other party will not have an adequate remedy at law or damages. Accordingly,
each party hereto agrees that injunctive relief or other equitable remedy, in
addition to remedies at law or damages, is the appropriate remedy for any such
failure and will not oppose the granting of such relief on the basis that the
other party has an adequate remedy at law. Each party hereto agrees that it will
not seek, and agrees to waive any requirement for, the securing or posting of a
bond in connection with any other party's seeking or obtaining such equitable
relief.

      5.2   Entire Agreement. This Agreement and the Standstill Agreement (as
herein amended) supersede all prior agreements, written or oral, among the
parties hereto with respect to the subject matter hereof and contains the entire
agreement among the parties with respect to the subject matter hereof. This
Agreement may not be amended, supplemented or modified, and no provisions hereof
may be modified or waived, except by an instrument in writing signed by all the
parties hereto. No waiver of any provisions hereof by any party shall be deemed
a waiver of any other provisions hereof by any such party, nor shall any such
waiver be deemed a continuing waiver of any provision hereof by such party.

      5.3   Notices. Any notice, request, instruction or other document to be
given hereunder by any party to the others shall be in writing and delivered
personally or sent by registered or certified mail, postage prepaid, or by
facsimile:


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               if to WMX, the Shareholder or Rust:

               Herbert A. Getz
               Waste Management, Inc.
               3003 Butterfield Road
               Oak Brook, Illinois  60523
               Telecopier:  (630) 572-9130

               with a copy to:

               John H. Bitner
               Bell, Boyd & Lloyd
               Three First National Plaza
               70 West Madison Street, Suite 3300
               Chicago, Illinois  60602-4207
               Telecopier:  (312) 372-2098

               if to the Company:

               Steven E. Harbour
               OHM Corporation
               5445 Triangle Parkway, Suite 400
               Norcross, Georgia  30092
               Telecopier:  (770) 849-3110

               with a copy to:

               Joseph B. Frumkin
               Sullivan & Cromwell
               125 Broad Street
               New York, New York 10004
               Telecopier:  (212) 558-3588

               and a copy to:

               Thomas C. Daniels
               Jones Day Reavis & Pogue
               North Point
               901 Lakeside Avenue
               Cleveland, Ohio 44114
               Telecopier:  (216) 579-0212


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               if to Parent:

               James G. Kirk
               International Technology Corporation
               2790 Mosside Boulevard
               Monroeville, PA  15146-2792
               Telecopier:  (412) 858-3978

               with a copy to:

               Peter F. Ziegler
               Gibson, Dunn & Crutcher LLP
               333 South Grand Avenue
               Los Angeles, California 90071
               Telecopier:  (213) 229-7520

or to such other persons or addresses as may be designated in writing by the
party to receive such notice as provided above.

      5.4   Miscellaneous.

            (a)   This Agreement shall be deemed a contract made under, and for
all purposes shall be construed in accordance with, the laws of the State of
Ohio applicable to agreements executed in and solely to be performed within such
State.

            (b)   If any provision of this Agreement or the application of such
provision to any person or circumstances shall be held invalid or unenforceable
by a court of competent jurisdiction, such provision or application shall be
unenforceable only to the extent of such invalidity or unenforceability and the
remainder of the provision held invalid or unenforceable and the application of
such provision to persons or circumstances, other than the party as to which it
is held invalid, and the remainder of this Agreement, shall not be affected.

            (c)   This Agreement may be executed in one or more counterparts,
each of which shall be deemed to be an original but all of which together shall
constitute one and the same instrument.

            (d)   This Agreement shall terminate automatically upon the
termination of the Merger Agreement. This Agreement may be terminated by the
Company at any time if


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WMX or the Shareholder shall have failed to comply with any of their respective
covenants or agreements contained in this Agreement. This Agreement may be
terminated by WMX or the Shareholder at any time if the Company shall have
failed to comply with any of its covenants or agreements contained in this
Agreement.

            (e)   Each party hereto shall execute and deliver such additional
documents as may be necessary or desirable to effect the transactions
contemplated by this Agreement.

            (f)   All Section headings herein are for convenience of reference
only and are not part of this Agreement, and no construction or reference shall
be derived therefrom.

            (g)   The obligations of the parties set forth in this Agreement
shall not be effective or binding upon any party hereto until after such time as
the Merger Agreement is executed and delivered by the Company, Parent and Merger
Sub, and the parties agree that there is not and has not been any other
agreement, arrangement or understanding between the parties hereto with respect
to the matters set forth herein.


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

                                   OHM CORPORATION



                                   By:__________________________________
                                      Name:
                                      Title:


                                   WASTE MANAGEMENT, INC.



                                   By:__________________________________
                                      Name:
                                      Title:


                                   RUST INTERNATIONAL INC.



                                   By:__________________________________
                                      Name:
                                      Title:


                                   RUST REMEDIAL SERVICES
                                     HOLDING COMPANY INC.



                                   By:__________________________________
                                      Name:
                                      Title:


   15
                                   INTERNATIONAL TECHNOLOGY
                                     CORPORATION



                                   By:__________________________________
                                      Name:
                                      Title:


   16
                                                                     (EXHIBIT A)


                                  FORM OF PROXY

      The undersigned, for consideration received, hereby appoints Anthony J.
DeLuca and James G. Kirk and each of them my proxies, with power of substitution
and resubstitution, to vote all shares of Common Stock of OHM Corporation, an
Ohio corporation (the "Company"), [and [insert any other Shares (as defined in
the Amended and Restated Share Repurchase Agreement) or other shares of capital
stock of the Company owned by the Shareholder)]] owned by the undersigned at the
Special Meeting of Shareholders of the Company to be held [insert date, time and
place] and at any adjournment thereof IN FAVOR OF adoption of the Agreement and
Plan of Merger, dated as of January 15, 1998 (the "Merger Agreement"), among the
Company, International Technology Corporation ("Parent") and IT-Ohio, Inc., IN
FAVOR OF consummation of the Merger Transactions, IN FAVOR OF [List such number
of Parent Representatives (as defined in Section 1.4 of the Merger Agreement) as
Parent is permitted to cause to be elected to the Company's Board of Directors
pursuant to Section 1.4 of the Merger Agreement], and AGAINST [insert
description of any action or agreement that would compete with, impede,
interfere with or attempt to discourage the Merger Transactions or inhibit the
timely consummation of the Merger Transactions or any action or agreement that
would result in a breach in any material respect of any covenant, representation
or warranty or any other obligation of the Company under the Merger Agreement or
any merger, consolidation, business combination, reorganization,
recapitalization, liquidation or sale or transfer of any material assets of the
Company or its subsidiaries]. This proxy is coupled with an interest, revokes
all prior proxies granted by the undersigned and is irrevocable until such time
as the Amended and Restated Share Repurchase Agreement, dated as of February __,
1998 among the undersigned and the Company terminates in accordance with its
terms.

                                   Dated _________, 1998

                                   RUST REMEDIAL SERVICES HOLDING
                                     COMPANY INC.


                                   By:__________________________________
                                      Name:
                                      Title: