
                                                                   EXHIBIT 10.13

                AGREEMENT AND SIXTH AMENDMENT TO CREDIT AGREEMENT
                               (February 29, 1996)

      THIS AGREEMENT AND SIXTH AMENDMENT TO CREDIT AGREEMENT (this "Amendment")
is made and entered into as of February 29, 1996 by and among ALLWASTE, INC.
(the "COMPANY"), a Delaware corporation, EACH OF THE FINANCIAL INSTITUTIONS
SIGNATORY HERETO (individually, a "BANK" and collectively, the "BANKS"), TEXAS
COMMERCE BANK NATIONAL ASSOCIATION ("TCB"), a national banking association
acting as agent for the Banks (in such capacity, together with its successors in
such capacity, the "AGENT"), and NATIONSBANK OF TEXAS, N.A., a national banking
association, as co-agent under the Credit Agreement (as defined hereinafter) (in
such capacity, the "CO-AGENT").

RECITALS:

      A. The Company, the Agent and the Banks have entered into a Credit
Agreement dated as of November 30, 1993 (which such Credit Agreement, as the
same may have heretofore been amended, modified, supplemented and restated from
time to time, is hereinafter called the "CREDIT AGREEMENT").

      B.    The Company,  the Agent,  the Co-Agent and the Banks now desire to
amend the Credit Agreement in certain respects as provided hereinbelow.

AGREEMENTS:

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

      1. FIXED CHARGE COVERAGE RATIO AMENDED. Section 5.3(c) of the Credit
Agreement is hereby amended in its entirety to be and read as follows:

            "(c) have at all times a FIXED CHARGE COVERAGE RATIO of not less
      than (1) 1.00 to 1.00 at all times from and including November 30, 1995
      through and including August 31, 1996 and (2) 1.10 to 1.00 at all times
      thereafter;"

      2. CAPITAL EXPENDITURE LIMITATIONS ADDED.  The Credit Agreement is hereby
amended by adding  thereto a new Section  6.15 which shall be and read as
follows:

            "6.15 CAPITAL EXPENDITURES. Make expenditures for fixed or capital
      assets on a consolidated basis during (a) the two (2) consecutive fiscal
      quarters of the Company ending May 31, 1996 in excess of $12,500,000 in
      the aggregate and (b) the three (3) consecutive fiscal quarters of the
      Company ending August 31, 1996 in excess of $18,000,000 in the aggregate;
      PROVIDED, that, in calculating said amount for any such period,
      expenditures for fixed or capital assets made by Subsidiaries of the
      Company, which were acquired during such period and accounted for as a
      pooling of interest, shall not be included to the extent that such
      expenditures were made prior to the time of acquisition). For purposes of
      determining the amount of expenditures made by the Company during any such
      period, such expenditures shall include the cost of any revenue producing
      equipment (including all vehicles) subject to any operating lease entered
      into during such period."

      3. AMENDMENT FEE PROVISIONS AMENDED. Section 2.16 of the Credit Agreement
is hereby amended by adding thereto after the word "waiver" where it appears in
the first sentence of that Section the phrase:

      "(including a waiver of any violation of capital expenditure limits
      imposed from time to time pursuant to SECTION 6.15 hereof)"

      In addition, Section 2.16 is amended to change the reference to Section
6.14 to Section 6.15 of the Credit Agreement.

NOTWITHSTANDING SECTION 2.16 OF THE CREDIT AGREEMENT, AS AMENDED BY THIS
SECTION, with respect to this Amendment, only, the amendment fee to be paid by
the Company to each Bank simultaneously with the execution and delivery of this
Amendment, shall be equal to one-eighth of one percent (1/8%) of such Bank's
Commitment as of the date hereof.

      4. GUARANTY PROTECTION PROVISIONS AMENDED.  Section  5.11  of  the Credit
Agreement is hereby amended by adding to the end thereof the following new
sentence:

      "Notwithstanding the foregoing, if the Rolling Four Quarter for any such
      day ends on February 29, 1996, May 31, 1996 or August 31, 1996, the phrase
      "twenty percent (20%)" where it appears in the foregoing sentence shall be
      deemed to be and read "twenty-two percent (22%)"."

      5. NON-GUARANTEEING SUBSIDIARY REPRESENTATIONS. The Company hereby
warrants and represents to the Agent, the Co-Agent and the Banks that all of the
Company's Subsidiaries which are Foreign Subsidiaries or Partially Owned
Subsidiaries as of the date of this Amendment which have not executed either a
Guaranty or a Joinder Agreement are identified as such on SCHEDULE I attached
hereto. The aggregate of the Net Income before taxes for the Rolling Four
Quarters as of the date hereof of all of the Non-Guaranteeing Subsidiaries does
not exceed as of the date hereof twenty-two percent (22%) of the Net Income
before taxes of the Company and its Subsidiaries on a consolidated basis for
such Rolling Four Quarters, nor does the aggregate of the Net Book Value of the
assets of such Subsidiaries exceed twenty-two percent (22%) of the Net Book
Value of the assets of the Company and its Subsidiaries on a consolidated basis
as of the date hereof. All of the Dormant Subsidiaries are designated as such on
SCHEDULE I attached hereto.

      6. DELIVERY OF CERTIFICATES OF EXISTENCE, GOOD STANDING, ETC. With respect
to each Guarantor, the Company hereby agrees to deliver to the Agent, within
thirty (30) days after the date hereof, certificates from the appropriate public
officials of each of the states where such Guarantor is incorporated and
conducts its business as to the continued existence, good standing and authority
to do business in those states.

      7. CONDITIONS. No part of this Amendment shall become effective until the
Company shall have delivered (or shall have caused to be delivered) to the Agent
each of the following, in Proper Form:

        (a) a certificate from the Secretary of State or other appropriate
            public official of the State of Delaware as to the continued
            existence and good standing of the Company in the State of Delaware;

        (b) a certificate from the Secretary of State or other appropriate
            public official of the State of Texas as to the qualification of the
            Company to do business in the State of Texas;

        (c) a certificate  from the Office of the  Comptroller of the State
            of Texas as to the  good  standing  of the  Company  in the  State
            of Texas;

        (d) a legal  opinion from the general  counsel for the Company and the
            Current  Guarantors  acceptable  to  the  Agent  in its  sole and
            absolute discretion;

        (e) certificates dated as of the date hereof of the Secretary or any
            Assistant Secretary of the Company and each of the Guarantors as of
            the date hereof, and such other documents and information as the
            Banks may request;

        (f) a Consent, in Proper Form, executed by of all of the Guarantors to
            the execution and delivery of this Amendment and such other related
            matters as the Banks may reasonably require;

        (g) a Notice of Entire  Agreement,  DTPA  Waiver and Release of Claims
            executed by the Company and each of the  Guarantors as of the date
            hereof, and

        (h) the amendment fee payable to each Bank a party to the Credit
            Agreement prior to the date hereof in the amount set opposite such
            Bank's signature line herein.

      8. REPRESENTATIONS TRUE; NO DEFAULT. The Company represents and warrants
that the representations and warranties contained in Section 4 of the Credit
Agreement and in the other Loan Documents are true and correct in all material
respects on and as of the date hereof as though made on and as of such date. The
Company hereby certifies that no Default or Event of Default under the Credit
Agreement or any of the other Loan Documents has occurred and is continuing as
of the date hereof.

      9. RATIFICATION. Except as expressly amended hereby, the Credit Agreement
and the other Loan Documents shall remain in full force and effect. In the event
of any conflict between this Amendment and the Credit Agreement or any of the
other Loan Documents (or any earlier modification of any of them), this
Amendment shall control. The Credit Agreement, as hereby amended, and all rights
and powers created thereby or thereunder and under the other Loan Documents are
in all respects ratified and confirmed and remain in full force and effect.

      10. DEFINITIONS AND REFERENCES. Terms used herein which are defined in the
Credit Agreement or in the other Loan Documents shall have the meanings therein
ascribed to them. The term "Credit Agreement" as used in the Credit Agreement,
the other Loan Documents or any other instrument, document or writing furnished
to the Agent, the Co-Agent or any of the Banks by the Company shall mean the
Credit Agreement as hereby amended.

      11. MISCELLANEOUS. This Amendment (a) shall be binding upon and inure to
the benefit of the Company, the Banks, the Agent, the Co-Agent and their
respective successors, assigns, receivers and trustees (provided, however, that
the Company shall not assign its rights hereunder without the prior written
consent of the Agent); (b) may be modified or amended only by a writing signed
by each party; (c) SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE
LAWS OF THE STATE OF TEXAS AND THE UNITED STATES OF AMERICA; (d) may be executed
in several counterparts, and by the parties hereto on separate counterparts, and
each counterpart, when so executed and delivered, shall constitute an original
agreement, and all such separate counterparts shall constitute but one and the
same agreement; and (e) together with the other Loan Documents, embodies the
entire agreement and understanding between the parties with respect to the
subject matter hereof and supersedes all prior agreements, consents and
understandings relating to such subject matter. The headings herein shall be
accorded no significance in interpreting this Amendment.

      IN WITNESS WHEREOF, the Company, the Banks, the Agent and the Co-Agent
have caused this Amendment to be signed by their respective duly authorized
officers, effective as of the date which first appears hereinabove.

                                          ALLWASTE, INC.,
                                          a Delaware corporation

                                          By:  /s/ T. WAYNE WREN
                                               T. Wayne Wren,
                                               Senior  Vice President

ATTEST:

/s/ WILLIAM L. FIEDLER
William L. Fiedler, Secretary


Attachments:

SCHEDULE I - Non-guaranteeing Subsidiaries
            and Dormant Subsidiaries

Amendment Fee: $50,000                    TEXAS COMMERCE BANK NATIONAL
                                            ASSOCIATION, a national
                                            banking association,
                                            as a Bank and as Agent

                                          By: /s/ RICHARD L. ESDORN, III
                                              Richard L. Esdorn, III,
                                              Senior Vice President


Amendment Fee: $37,500                    NATIONSBANK OF TEXAS, N.A.,
                                             a national banking  association,
                                             as a  Bank and as Co-Agent

                                          By: /s/ RICHARD L. NICHOLS, JR.
                                          Name: Richard R. Nichols, Jr.
                                          Title: Vice President


Amendment Fee: $12,500                    BANK OF AMERICA TEXAS, N.A.,
                                            a national banking association

                                          By: /s/ VICTOR N. TEKELL
                                              Victor N. Tekell, Vice President


Amendment Fee: $18,750                    FIRST INTERSTATE BANK OF TEXAS,
                                            N.A, a national banking
                                            association

                                          By: /s/ DAVID M. ANDERSON
                                          Name: David M. Anderson
                                          Title: Vice President


Amendment Fee: $18,750                    THE BANK OF NOVA SCOTIA

                                          By: /s/ F.C.H. ASHBY
                                          Name: F.C.H. Ashby
                                          Title: Senior Manager Loan Operations


Amendment Fee: $25,000                    COMERICA BANK - TEXAS,
                                             a Texas banking association

                                          By: /s/ MITCHELL SCHULMAN
                                              Mitchell Schulman,
                                              Vice President


Amendment Fee: $25,000                    LTCB TRUST COMPANY, a New York
                                            Trust Company

                                          By: /s/ JOHN J. SULLIVAN
                                          Name: John J. Sullivan
                                          Title: Executive Vice President


Amendment Fee: $12,500                    ABN AMRO BANK N.V., HOUSTON
                                            AGENCY

                                          By: ABN AMRO North America, Inc.,
                                              as agent

                                          By: /s/ LILA JORDAN
                                          Name: Lila Jordan
                                          Title: Vice President & Director

                                          By: /s/ DIEGO PUIGGARI
                                          Name: Diego Puiggari
                                          Title: Vice President & Director
<PAGE>
                                 ALLWASTE, INC.
                                   SCHEDULE I

CALIGO REINGUNGSGES M.B.H.  (AUSTRIAN)

770950 ONTARIO LIMITED  (CANADIAN)

ALLWASTE ENVIRONMENTAL SERVICES OF SARNIA, LTD.  (CANADIAN)

ALLWASTE OF CANADA LTD.  (CANADIAN)

CALIGO RECLAMATION LTD.  (CANADIAN)

CANADIAN CARGO CLEAN, LTD.  (CANADIAN) (DORMANT)

ENVIRO-JET SYSTEMS, INC.  (CANADIAN)

HONEY-BEE SANITATION INC.  (CANADIAN)

ALLWASTE SERVICIOS INDUSTRIALES DE CONTROL ECOLOGICO, S.A. DE C.V.  (MEXICAN)

ALLWASTE TANK SERVICES, S.A. DE C.V.  (MEXICAN)

CALIGO DE MEXICO, S.A. DE C.V.  (MEXICAN)

ALLWASTE ASBESTOS ABATEMENT OF NEW ENGLAND, INC.  (DORMANT)

ALLWASTE ENVIRONMENTAL SERVICES/NORTH CENTRAL, INC., AN ILLINOIS CORPORATION
 (DORMANT)

