1
                                                                   Exhibit 10.41
                                                                   -------------


                                 THIRD AMENDMENT
                           Dated as of August 12, 1997
                                       to
                               SECURITY AGREEMENT
                            Dated as of May 11, 1993


                  This THIRD AMENDMENT TO SECURITY AGREEMENT dated as of August
12, 1997 (this "Amendment") is entered into by and among OHM Corporation
("OHM"), OHM Remediation Services Corp. ("Remediation", and together with OHM,
the "Borrowers"), Beneco Enterprises Inc. ("Beneco"), Citicorp USA, Inc., as
administrative agent (in such capacity, the "Administrative Agent") and Bank of
America National Trust and Savings Association (successor by merger to Bank of
America Illinois), as issuing and paying agent and as co-agent (in such
capacity, the "Issuing and Paying Agent") on behalf of the "Banks" parties to
the "Credit Agreement" referred to below. Capitalized terms used herein and not
otherwise defined herein shall have the respective meanings ascribed to such
terms in the Credit Agreement referred to below.


                              PRELIMINARY STATEMENT
                              --------------------

                  A. The Borrowers entered into that certain Revolving Credit
Agreement dated as of May 31, 1995 with the financial institutions from time to
time party thereto (the "Banks"), the Administrative Agent and the Issuing and
Paying Agent (as such Revolving Credit Agreement has been or may hereafter be
amended, restated, supplemented or otherwise modified from time to time, the
"Credit Agreement").

                  B. The Borrowers and Analytical Services Corp., an affiliate
of the Borrowers, executed that certain Security Agreement dated as of May 11,
1993 (as such Security Agreement has previously been amended, the "Security
Agreement") in favor of the Issuing and Paying Agent. Pursuant to the Second
Amendment to the Security Agreement dated as of May 31, 1995, Analytical
Services Corp. was removed as a party to the Security Agreement.

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

                  D. Pursuant to SECTION 5.01(g) of the Credit Agreement, Beneco
is required to grant a secured guaranty to secure the Obligations.

                  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:



   2



                  SECTION 1. AMENDMENTS TO THE SECURITY AGREEMENT. The Security
Agreement is hereby amended as follows:

                  (a) Each reference in the Security Agreement to the Grantors
is hereby amended to add and include Beneco.

                  (b) The Schedule to the Security Agreement is hereby amended
and restated in its entirety as set forth in ANNEX I hereto.

                  (c) Clause (iii) in Section 3 of the Security Agreement (up to
but not including the parenthetical following clause (iii)) is amended and
restated as follows:

                  "(iii) in the case of Beneco, all obligations under the
         Guaranty dated August 12, 1997 executed by Beneco in favor of the
         Issuing and Paying Agent and the Administrative Agent for the benefit
         of the Banks"

                  SECTION 2. ASSUMPTION OF OBLIGATIONS BY BENECO. Beneco hereby
(i) expressly assumes each of the liabilities, and agrees to be bound by the
obligations, of a Grantor under the Security Agreement, (ii) expressly makes
each warranty and representation of a Grantor set forth in the Security
Agreement except that with respect to the representation under SECTION 5(d) of
the Security Agreement, the security interest granted under the Security
Agreement in the assets of Beneco is subject to a prior blanket lien in favor of
West One Bank, Utah as evidenced by financing statement file no. 218443 filed
with the State of Utah Division of Corporations and Commercial Code on September
12, 1989 (as amended and continued), and (iii) expressly grants, pledges and
assigns to the Issuing and Paying Agent, for its benefit and the ratable benefit
of the Banks, the Issuing Banks and the Administrative Agent, a continuing
security interest in, lien on, assignment of, and right of set-off against, all
of its right, title and interest in and to any property, whether now owned or
hereafter acquired or arising and wheresoever located, which is of a type
described in Section 2 of the Security Agreement (all of which shall thereby be
and become Collateral for all purposes).


                  SECTION 3. REAFFIRMATION AND EFFECT ON THE SECURITY AGREEMENT.
                             ---------------------------------------------------

                  3.1 The Borrowers hereby reaffirm their obligations under the
Security Agreement, which, except to the extent expressly amended hereby,
remains in full force and effect.

                  3.2 Upon the effectiveness of this Amendment, each reference
in the Security Agreement to "this Agreement," "hereunder," "hereof," "herein,"
or words of like import shall mean and be a reference to the Security Agreement
as amended hereby, and each reference to the Security Agreement in any of the
Transaction Documents and any other document, instrument or

                                      - 2 -

   3



agreement executed and/or delivered in connection with the Security Agreement
shall mean and be a reference to the Security Agreement as amended hereby.

                  3.3 Except as specifically set forth herein, the Security
Agreement, each of the other Transaction Documents and all other documents,
amendments, instruments and agreements executed and/or delivered in connection
therewith shall remain in full force and effect and are hereby ratified and
confirmed.

                  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 Security 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 INTERNAL LAWS (AS OPPOSED TO THE CONFLICT
OF LAWS PROVISIONS) 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.



                      [This space intentionally left blank]

                                      - 3 -

   4


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

Steve E. Harbour
- -------------------------
Secretary
                                      OHM REMEDIATION SERVICES CORP.


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



                                      BENECO ENTERPRISES INC.


                                      By  Scott Doxey
                                          -------------------------------------
                                                 Title:  Treasurer



                                      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


                                      - 4 -