JOINDER AGREEMENT

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EXHIBIT 4.28M

JOINDER AGREEMENT

        JOINDER AGREEMENT, dated as of February 27, 2009, made by ENVIROSORT INC., an Alberta corporation (the " Additional Canadian Borrower "), in favor of (a) CREDIT SUISSE, Cayman Islands Branch, as LC Facility Collateral Agent and LC Facility Administrative Agent (in such capacity, the " LC Facility Administrative Agent ") for the benefit of the LC Facility Secured Parties (as defined in the Credit Agreement (as defined below)) and (b) BANK OF AMERICA, N.A., as administrative agent for the Revolving Facility (in such capacity, the " Revolving Administrative Agent " and together with the LC Facility Administrative Agent, the " Administrative Agents ") and BANK OF AMERICA, N.A. (Canada Branch) (as successor in interest to BABC Global Finance, Inc.), as Canadian Collateral Agent (in such capacity, the " Canadian Collateral Agent ") for the benefit of the Revolving Secured Parties (as defined in the Credit Agreement). All capitalized terms not defined herein shall have the meanings given to them in such Credit Agreement.

W I T N E S S E T H:

        WHEREAS, Clean Harbors, Inc., a Massachusetts corporation (the " Parent "), the other Credit Parties, the LC Facility Administrative Agent, Bank of America, N.A. ("BANA "), as Revolving Administrative Agent, Banc of America Securities LLC, as sole arranger under the Revolving Facility, BANA, as syndication agent under the LC Facility, Credit Suisse, as sole bookrunner under the LC Facility, and Credit Suisse and BAS, as joint lead arrangers under the LC Facility, have entered into an Amended and Restated Loan and Security Agreement, dated as of June 30, 2004, amended as of July 20, 2005, amended and restated as of December 1, 2005, supplemented by the Term Loan Supplement dated as of August 18, 2006, and amended through and as of June 25, 2008 (as the same may be further amended, restated, modified and/or supplemented from time to time, the " Credit Agreement ");

        WHEREAS, the Additional Canadian Borrower hereby confirms the grant to the Canadian Collateral Agent of the security interests in the Canadian Accounts Collateral for the benefit of itself and each other Canadian Secured Party pursuant to Section 5.2 of the Credit Agreement; and

        WHEREAS, this Joinder Agreement is executed and delivered pursuant to the Credit Agreement;

        NOW, THEREFORE, IT IS AGREED:

        1.     Credit Agreement.     (a)    In accordance with Section 9.26(b) of the Credit Agreement, by executing and delivering this Joinder Agreement, the Additional Canadian Borrower hereby becomes a Canadian Borrower under the Credit Agreement from and after the date hereof with the same force and effect as if originally a "Canadian Borrower" under the Credit Agreement. Without limiting the generality of the foregoing, the Additional Canadian Borrower hereby expressly agrees to observe and perform and be bound by all of the terms, covenants, representations, warranties, and agreements contained in the Credit Agreement which are binding upon, and to be observed or performed by, a Canadian Borrower.

        (b)   The Additional Canadian Borrower acknowledges and agrees that all Canadian Loans made under the Credit Agreement are made to or for the mutual benefit, directly and indirectly, of each of the Canadian Borrowers and in consideration of the agreement of the US Credit Parties and the other Canadian Borrowers to accept joint and several liability for the Canadian Obligations. The Additional Canadian Borrower hereby irrevocably and unconditionally accepts, not merely as a surety but also as a co-debtor, joint and several and direct and primary liability for the full and indefeasible payment when due and performance of all Canadian Obligations and for the prompt and full payment and performance of all of the promises, covenants, representations, and warranties made or undertaken by each Canadian Borrower under the Financing Agreements, and agrees that such liability is independent of the duties, obligations, and liabilities of each of the joint and several Canadian Borrowers. In furtherance of the foregoing, the Additional Canadian Borrower jointly and severally, absolutely and unconditionally guarantees to the Canadian Secured Parties the full and indefeasible payment and performance when due of all Canadian Obligations.

        (c)   The Additional Canadian Borrower acknowledges and agrees that (i) any Secured Party may enforce its rights under the Credit Agreement independently as to each Credit Party and independently of any other remedy or security, (ii) any Secured Party at any time may have or hold in connection with the Obligations, and (iii) it shall not be necessary for any Secured Party to marshal assets in favor of any Credit Party or to proceed upon or against or exhaust any security or remedy before proceeding to enforce the Credit Agreement. The Additional Canadian Borrower expressly waives any right to require any Secured Party to marshal assets in favor of any Credit Party of the Obligations of such Additional Canadian Borrower or to proceed against any other Credit Party, and agrees the Canadian Collateral Agent may proceed against the Canadian Borrowers or any Canadian Accounts Collateral in such order as the Canadian Collateral Agent shall determine in its sole and absolute discretion.

        (d)   The Additional Canadian Borrower acknowledges and agrees any Secured Party may each file a separate action or actions against any Credit Party with respect to such Credit Party's Obligations, whether such action is brought or prosecuted with respect to any security or against any guarantor of such Credit Party, or whether any other person is joined in any such action or actions. The Additional Canadian Borrower agrees that any of the Secured Parties and any Credit Party and any affiliate of any Credit Party may deal with each other in connection with the Obligations or otherwise, or alter any contracts or agreements now or hereafter existing between any of them, in any manner whatsoever, all without in any way altering or affecting the continuing efficacy of this Agreement. The Additional Canadian Borrower, as a joint and several Credit Party and guarantor hereunder with respect to the Additional Canadian Borrower's Obligations, expressly waives the benefit of any statute of limitations affecting its joint and several liability and guarantee hereunder (but not its primary liability) or the enforcement of the Obligations of the Additional Canadian Borrower or any rights of any Secured Party created or granted herein.

        (e)   The Additional Canadian Borrower acknowledges that its obligations undertaken herein consist, in part, of the guarantee of obligations of the other Canadian Borrowers and, in full recognition of that fact and in full recognition of the joint and several and direct and primary liability of the Additional Canadian Borrower hereunder for the Canadian Obligations, the Additional Canadian Borrower consents and agrees that the Canadian Collateral Agent and the Canadian Lender may, at any time and from time to time, without notice or demand (except as provided in and in accordance with the terms of the Credit Agreement), whether before or after any actual or purported termination, repudiation or revocation of the Credit Agreement by any Credit Party, and without affecting the enforceability or continuing effectiveness of the Credit Agreement as to each Credit Party (including the Additional Canadian Borrower): (i) increase, extend, or otherwise change the time for payment or the terms of the Obligations or any part thereof; (ii) supplement, restate, modify, amend, increase, decrease, or waive, or enter into or give any agreement, approval or consent with respect to any of the Obligations or any part thereof, or any of the Financing Agreements or any additional security or guarantees, or any condition, covenant, default, remedy, right, representation, or term thereof or thereunder; (iii) accept new or additional instruments, documents, or agreements in exchange for or relative to any of the Financing Agreements or the Obligations or any part thereof; (iv) accept partial payments on any of the Obligations; (v) receive and hold additional security or guarantees for the Obligations or any part thereof; (vi) release, reconvey, terminate, waive, abandon, fail to perfect, subordinate, exchange, substitute, transfer, or enforce any security or guarantees, and apply any security and direct the order or manner of sale thereof as the Canadian Collateral Agent in its sole and absolute discretion may determine; (vii) release any person from any personal liability with respect to the Obligations or any part thereof; (viii) settle, release on terms satisfactory to the Canadian Collateral Agent or by operation of applicable laws or otherwise liquidate or enforce any Obligations and any security therefor or guaranty thereof, respectively, in any manner, consent to the transfer of any security and bid and purchase at any sale; or (ix) consent to the merger, change, or any other restructuring or termination of the corporate or partnership existence of any Credit Party, and correspondingly restructure the Obligations, and any such merger, change, restructuring, or termination

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