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                                                                   Exhibit 10(f)



                                                                  EXECUTION COPY



                                FIRST AMENDMENT
                            Dated as of May 31, 1995
                                       to
                                PLEDGE AGREEMENT
                            Dated as of May 11, 1993


                 This FIRST AMENDMENT TO PLEDGE AGREEMENT dated as of May 31,
1995 (this "Amendment") is entered into by and between OHM Corporation, an Ohio
corporation (the "Pledgor"), and Bank of America Illinois ("BAI"), 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 11, 1993 (as previously
amended and otherwise modified, the "Prior Credit Agreement") with the
financial institutions from time to time party thereto, BAI (formerly known as
Continental Bank N.A.) in its separate capacities as the administrative agent
and issuing bank thereunder, and Citicorp USA, Inc.  ("Citicorp"), in its
capacity as agent thereunder.

                 B.       In connection with the Prior Credit Agreement, the
Pledgor executed that certain Pledge Agreement dated as of May 11, 1993 (as
previously amended and otherwise modified, the "Pledge Agreement") in favor of
the "Administrative Agent" thereunder.

                 C.       The Prior Credit Agreement has been substituted and
replaced by that certain Revolving Credit Agreement dated as of May 31, 1995
(as amended, restated, supplemented or otherwise modified from time to time,
the "Credit Agreement") among the Borrowers, the financial institutions from
time to time party thereto as banks (the "Banks"), the Issuing and Paying Agent
and Citicorp, in its capacity as administrative agent (the "Administrative
Agent") for the Banks.

                 D.       In connection with the Credit Agreement, the
Borrowers, the Banks, the Issuing and Paying Agent and the Administrative Agent
have agreed that the Pledge Agreement is to be amended as set forth herein.

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                 E.       Capitalized terms used herein and not otherwise
defined herein shall have the respective meanings ascribed to such terms in the
Credit Agreement.

                 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.

                 1.1  General Definitions.  Capitalized terms used in the
Pledge Agreement and defined in the Credit Agreement shall have the respective
meanings ascribed to such terms in the Credit Agreement.

                 1.2  Replaced Terms.  As used in the Pledge Agreement, each of
the following terms shall be deemed to be replaced as follows:

                          (a)  The term Administrative Agent shall be replaced
         by and shall mean and be a reference to the term Issuing and Paying
         Agent.

                          (b)  The term Agent shall be replaced by and shall
         mean and be a reference to the term Administrative Agent.

                          (c)  The term Issuing Bank shall be replaced by and
         shall mean and be a reference to the term Issuing Banks.

                 1.3  Other Changes.

                          (a)  Each reference in the Pledge Agreement to the
         Credit Agreement shall mean and be a reference to the Credit Agreement
         as defined herein, and each reference in the Pledge Agreement to a
         section or provision of the Prior Credit Agreement shall mean and be a
         reference to the corresponding section or provision of the Credit
         Agreement.

                          (b)  Schedule I to the Pledge Agreement is hereby
         amended to (i) delete the reference to Analytical Services Corp.
         therein and (ii) delete the number "3,710,000" opposite the reference
         to NSC Corporation therein and to substitute therefor "4,010,000".


                 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 Effective Date of the Credit Agreement as if made on and as of such
date.



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                 SECTION 3.  EFFECT ON THE PLEDGE AGREEMENT.

                 3.1  Upon the effectiveness of this Amendment, 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.

                 3.2  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.

                 3.3  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 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.



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                 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.

                                                   OHM CORPORATION


Attest:                                            By___________________________
                                                     Title:  Treasurer

________________________
Secretary



                                                   BANK OF AMERICA ILLINOIS, as
                                                     Issuing and Paying Agent


                                                   By___________________________
                                                     Title:  Vice President



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