Exhibit 4.10

                                  June 20, 1997


CLEAN HARBORS ENVIRONMENTAL
    SERVICES, INC.
CLEAN HARBORS TECHNOLOGY
    CORPORATION
CLEAN HARBORS KINGSTON FACILITY
    CORPORATION
CLEAN HARBORS OF BRAINTREE, INC.
CLEAN HARBORS SERVICES, INC.
CLEAN HARBORS OF NATICK, INC.
CLEAN HARBORS OF CONNECTICUT, INC.
MURPHY'S WASTE OIL SERVICE, INC.
CLEAN HARBORS OF CLEVELAND, INC.
MR. FRANK, INC.
SPRING GROVE RESOURCE RECOVERY, INC.

    Re:  Fourth Amendment to Financing Agreements ("Fourth Amendment")

Gentlemen:

    Reference is made to the Loan and Security Agreement dated May 8, 1995, 
as amended, between you and the undersigned (the "Loan Agreement"). All 
capitalized terms not otherwise defined herein shall have the meanings given 
such terms in the Loan Agreement.

    Borrowers have requested an extension of the term of the Financing 
Agreements to May 8, 1999 and amendments to certain of the covenants therein. 
Subject to the terms and conditions hereof, the Lender agrees with the 
Borrowers as follows:

    (1) The first sentence of Section 12.1(a) of the Loan Agreement is 
deleted and replaced with the following sentence:

          "This Agreement and the other Financing Agreements shall
          become effective as of the date set forth on the first page
          hereof and shall continue in full force and effect for a term
          ending on the date four (4) years from the date hereof (the
          "Renewal Date"), and from year to year thereafter, unless
          sooner terminated pursuant to the terms hereof; provided,
          that, Lender may, at its option, extend the Renewal Date to
          the date five (5) years from the date hereof by giving
          Borrower notice at least one hundred twenty (120) days prior
          to the fourth anniversary of this Agreement."

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    (2) Section 12.1(c) of the Loan Agreement is deleted in its entirety and 
replaced with the following:

          "If for any reason this Agreement is terminated prior to the
          end of the then current term or renewal term of this
          Agreement, in view of the impracticality and extreme
          difficulty of ascertaining actual damages and by mutual
          agreement of the parties as to a reasonable calculation of
          Lender's lost profits as a result thereof, Borrower agrees to
          pay to Lender, upon the effective date of such termination, an
          early termination fee in the amount of (i) 1% of the Revolving
          Credit Limit if such termination is effective in the period
          May 9, 1997 to and including May 8, 1998, and (ii) .5% of the
          Revolving Credit Limit if such termination is effective in the
          period May 9, 1998 to and including May 8, 1999. Such early
          termination fee shall be presumed to be the amount of damages
          sustained by Lender as a result of such early termination and
          Borrower agrees that it is reasonable under the circumstances
          currently existing. The refinancing and repayment of the Term
          Loan through the issuance of pollution control authority
          industrial revenue bonds shall not trigger the payment of the
          early termination fee. The early termination fee provided for
          in this Section 12.1 shall be deemed included in the
          Obligations."

    (3) Section 9.13 of the Loan Agreement is deleted in its entirety and 
replaced with the following:

        "Parent shall, at all times, maintain Working Capital of not less 
        than $10,000,000.00."

    (4) Section 9.14 of the Loan Agreement is deleted in its entirety 
and replaced with the following:

        "Parent shall, at all times, maintain Adjusted Net Worth of not less 
        than $40,000,000.00."

    (5) This Fourth Amendment and the Lender's obligations hereunder shall 
not be effective until each of the following conditions are satisfied:

        (a) all requisite corporate action and proceedings of the Borrowers 
in connection with this Fourth Amendment shall be satisfactory in form and 
substance to Lender and Lender shall receive certified copies of such 
corporate action and proceedings as Lender may request;

        (b) no material adverse change shall have occurred in the assets, 
business or prospects of any Borrower since the date of the most recent 
financial statements furnished to Lender pursuant to the Loan Agreement and 
no change or event shall have occurred which would impair the ability of any 
Borrower or any Obligor to 

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perform its obligations under the Loan Agreement or any of the other Financing
Agreements or of Lender to enforce the Obligations or to realize upon the
Collateral; and

        (c) Borrowers shall pay to Lender, and directs Lender to debit its 
loan account for, an additional facility fee equal to $50,000.00, which fee 
shall be fully earned and non-refundable on the date hereof.

    (6) Each Borrower confirms and agrees that (a) all representations and 
warranties contained in the Loan Agreement and in the other Financing 
Agreements are on the date hereof true and correct in all material respects 
(except for changes that have occurred as permitted by the covenants in 
Section 9 of the Loan Agreement), and (b) it is unconditionally and jointly 
and severally liable for the punctual and full payment of all Obligations, 
including, without limitation, all charges, fees, expenses and costs 
(including attorneys' fees and expenses) under the Financing Agreements, and 
that no Borrower has any defenses, counterclaims or setoffs with respect to 
full, complete and timely payment of all Obligations.

    (7) Each Guarantor, for value received, hereby assents to the Borrowers' 
execution and delivery of this Amendment, and to the performance by the 
Borrowers of their respective agreements and obligations hereunder. This 
Amendment and the performance or consummation of any transaction or matter 
contemplated under this Amendment, shall not limit, restrict, extinguish or 
otherwise impair any of the Guarantor's liability to Lender with respect to 
the payment and other performance obligations of the Guarantors pursuant to 
the Guarantees, dated May 8, 1995 executed for the benefit of Lender. Each 
Guarantor acknowledges that it is unconditionally liable to Lender for the 
full and complete payment of all Obligations including, without limitation, 
all charges, fees, expenses and costs (including attorney's fees and 
expenses) under the Financing Agreements and that such Guarantor has no 
defenses, counterclaims or setoffs with respect to full, complete and timely 
payment of any and all Obligations.

    (8) Borrowers hereby agree to pay to Lender all reasonable attorney's 
fees and costs which have been incurred or may in the future be incurred by 
Lender in connection with the negotiation and preparation of this Amendment 
and any other documents and agreements prepared in connection with this 
Amendment. The undersigned confirm that the Financing Agreements remain in 
full force and effect without amendment or modification of any kind, except 
for the amendments explicitly set forth herein. The undersigned further 
confirm that no Event of Default or events which with notice or the passage 
of time or both would constitute an Event of Default have occurred and are 
continuing. The execution and delivery of this Amendment by Lender shall not 
be construed as a waiver by Lender of any Event of Default under the 
Financing Agreements. This Amendment shall be deemed to be a Financing 
Agreement and, together with the other Financing Agreements, constitute the 
entire agreement between the parties with respect to the subject matter 
hereof and supersedes all prior dealings, correspondence, conversations or 
communications between the parties with respect to the subject matter hereof.

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    If you accept and agree to the foregoing please sign and return the 
enclosed copy of this letter. Thank you.

                                Very truly yours,

                                CONGRESS FINANCIAL CORPORATION
                                (NEW ENGLAND)


                                By:   /s/ KATHLEEN J. MERRITT
                                   --------------------------------------
                                   Name:  Kathleen J. Merritt
                                        ---------------------------------
                                   Title: Assistant Vice President
                                         --------------------------------
AGREED:

CLEAN HARBORS ENVIRONMENTAL
    SERVICES, INC.
CLEAN HARBORS TECHNOLOGY
    CORPORATION
CLEAN HARBORS KINGSTON FACILITY
    CORPORATION
CLEAN HARBORS OF BRAINTREE, INC.
CLEAN HARBORS SERVICES, INC.
CLEAN HARBORS OF NATICK, INC.
CLEAN HARBORS OF CONNECTICUT, INC.
MURPHY'S WASTE OIL SERVICE, INC.
CLEAN HARBORS OF CLEVELAND, INC.
MR. FRANK, INC.
SPRING GROVE RESOURCE RECOVERY, INC.


By:    /s/ STEVEN MOYNIHAN
   ----------------------------------------
   Name:   Steven Moynihan
   Title:  Senior Vice President



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GUARANTORS:

CLEAN HARBORS, INC.

By:  /s/  STEVEN MOYNIHAN
   ----------------------------------------
   Name:  Steven Moynihan
   Title: Senior Vice President


CLEAN HARBORS OF BALTIMORE, INC.


By:   /s/ STEVEN MOYNIHAN
   ----------------------------------------
   Name:  Steven Moynihan
   Title: Senior Vice President


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