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                                                                   Exhibit 10.42
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                                SECOND AMENDMENT
                           Dated as of August 12, 1997
                                       to
                                PLEDGE AGREEMENT
                            Dated as of May 11, 1993


                  This SECOND AMENDMENT TO PLEDGE AGREEMENT dated as of August
12, 1997 (this "Amendment") is entered into by and between OHM Corporation, an
Ohio corporation (the "Pledgor"), and Bank of America National Trust and Savings
Association (successor by merger to Bank of America Illinois) as issuing and
paying agent (in such capacity, the "Issuing and Paying Agent") on behalf of the
"Banks" parties to the "Credit Agreement" referred to below.


                             PRELIMINARY STATEMENT:
                             ----------------------

                  A. The Pledgor and OHM Remediation Services Corp., an Ohio
corporation (together with the Pledgor, the "Borrowers"), entered into that
certain Revolving Credit Agreement dated as of May 31, 1995 (as such Revolving
Credit Agreement has been or hereafter may be amended, restated, supplemented or
otherwise modified from time to time, the "Credit Agreement") with the financial
institutions from time to time party thereto (the "Banks"), Citicorp USA, Inc.
as administrative agent thereunder (in its capacity as administrative agent, the
"Administrative Agent"), and the Issuing and Paying Agent.

                  B. The Pledgor executed that certain Pledge Agreement dated as
of May 11, 1993 (as such Pledge Agreement has previously been amended pursuant
to that certain First Amendment to Pledge Agreement dated as of May 31, 1995,
the "Pledge Agreement") in favor of the Issuing and Paying Agent.

                  C. On or about June 18, 1997, the Pledgor acquired the stock
of Beneco Enterprises Inc. ("Beneco") for an aggregate consideration of
$15,000,000.

                  D. The Administrative Agent has requested that the Pledgor
pledge the stock of Beneco to the Issuing and Paying Agent, and pursuant to
Section 5.01(g) of the Credit Agreement, the Pledgor is obligated to pledge such
stock to the Issuing and Paying Agent.

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


                  SECTION 1. AMENDMENTS TO THE PLEDGE AGREEMENT.
                             -----------------------------------

                  Subject to the satisfaction of the conditions precedent set
forth in SECTION 3 of the Credit Agreement Amendment, the Pledge Agreement is
hereby amended as follows:



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                  1.1 Each reference in the Pledge Agreement to the Corporations
is hereby amended to add and include Beneco.

                  1.2 Schedule I to the Pledge Agreement is hereby amended and
restated in the form attached to this Amendment.


                  SECTION 2. REPRESENTATIONS AND WARRANTIES.
                             -------------------------------

                  The Pledgor hereby represents and warrants that each of the
representations and warranties set forth in Section 5 of the Pledge Agreement
are true and correct on and as of the date hereof as if made on and as of such
date.


                  SECTION 3. PLEDGE, REAFFIRMATION AND EFFECT ON THE PLEDGE
                             ----------------------------------------------
                             AGREEMENT.
                             ----------

                  3.1 The Pledgor hereby pledges to the Issuing and Paying
Agent, and grants to the Issuing and Paying Agent a security interest in, in
each case, for its benefit and for the benefit of the Administrative Agent, the
Banks and each Issuing Bank, the shares of capital stock of Beneco, now or at
any time or times hereafter owned by the Pledgor, and the certificates
representing any such shares, all options and warrants for the purchase of
shares of stock of Beneco now or hereafter held in the name of Pledgor, all of
which shall be part of the Pledged Stock under the Pledge Agreement, and all
dividends, cash, instruments and other property from time to time received,
receivable or otherwise distributed in respect of, or in exchange for any of the
foregoing, all of which shall be part of the Pledged Collateral under the Pledge
Agreement. The Pledgor hereby reaffirms its obligations under the Pledge
Agreement, which remains in full force and effect (including, without
limitation, with respect to the "Obligations" of the Borrowers under the Credit
Agreement).

                  3.2 Upon the effectiveness of this Agreement, each reference
in the Pledge Agreement to "this Agreement," "hereunder," "hereof," "herein," or
words of like import shall mean and be a reference to the Pledge Agreement as
amended hereby, and each reference to the Pledge Agreement in any of the
Transaction Documents and any other document, instrument or agreement executed
and/or delivered in connection with the Pledge Agreement shall mean and be a
reference to the Pledge Agreement as amended hereby.

                  3.3 Except as specifically set forth herein, the Pledge
Agreement shall remain in full force and effect and is hereby ratified and
confirmed. Without limiting the generality of the foregoing, the Pledgor hereby
acknowledges and agrees that the grant of Liens and security interests contained
in the Pledge Agreement shall run in favor of the Issuing and Paying Agent for
the benefit of itself, the Banks and the Administrative Agent, and shall
constitute security for the prompt payment and performance of the Obligations
under the Credit Agreement and the other Transaction Documents.

                  3.4 The execution, delivery and effectiveness of this
Amendment shall not operate as a waiver of any right, power or remedy of the
Issuing and Paying Agent under the

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Pledge Agreement or any other document, instrument or agreement executed in
connection therewith, nor constitute a waiver of any provision contained
therein, except as specifically set forth herein.


                  SECTION 4. EXECUTION IN COUNTERPARTS. This Amendment may be
executed by the parties hereto in separate counterparts, each of which when so
executed and delivered shall be deemed to be an original and all of which taken
together shall constitute but one and the same instrument.


                  SECTION 5. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS (INCLUDING SECTION 5-1401 OF THE
GENERAL OBLIGATIONS LAWS BUT OTHERWISE WITHOUT REGARD TO CONFLICT OF LAWS
PROVISIONS) AND DECISIONS OF THE STATE OF NEW YORK.


                  SECTION 6. SECTION TITLES. Section titles in this Amendment
are included herein for convenience of reference only and shall not affect in
any way the interpretation of any of the provisions hereof.


                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed by their respective officers thereunto duly authorized
as of the day and year first written above.


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                                           OHM CORPORATION


                                           By  Pamela K.M. Beall
                                               ------------------------------
                                             Title:  Treasurer
Attest:


Steven E. Harbour 
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Secretary

                                           BANK OF AMERICA NATIONAL TRUST AND
                                           SAVINGS ASSOCIATION
                                           (successor by merger to Bank of
                                           America Illinois), 
                                             as Issuing and Paying Agent


                                           By Jay McKeown
                                              ------------------------------
                                              Title:  Vice President




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