Exhibit 5.1

DAVIS, MALM & D'AGOSTINE, P.C.
ONE BOSTON PLACE
BOSTON, MA 02108
TEL. 617-367-2500

August 22, 2005

Clean Harbors, Inc.
1501 Washington Street
Braintree, MA 02184

Re:

Registration Statement on Form S-3

Ladies and Gentlemen:

        You are seeking to register 2,057,940 shares (the "Shares") of Common Stock, $.01 value per share, of Clean Harbors, Inc., a Massachusetts corporation (the "Company"), under the Securities Act of 1933, as amended, pursuant to a Registration Statement on Form S-3 (File No. 333-126205) which you have filed with the Securities and Exchange Commission (the "Commission"). Such Registration Statement, as amended by Amendment No. 1 thereto and as it may hereafter be further amended, is referred to hereafter as the "Registration Statement", and the form of prospectus included in, or filed under, the Registration Statement is referred to hereafter as the "Prospectus." As described in the Prospectus, you propose to issue the Shares to the Selling Shareholders (the "Selling Shareholders") described under "Selling Shareholders" in the Prospectus upon exercise by the Selling Shareholders of the Common Stock Purchase Warrants (the "Warrants") now held by them, and the Selling Shareholders propose to offer the Shares for sale from time to time as described under "Plan of Distribution" in the Prospectus. You have requested that we furnish to you an opinion as to the legality of the Shares, which opinion will be filed as an Exhibit to the Registration Statement.

        We have examined the Restated Articles of Organization and By-Laws of the Company, as amended, copies of votes of the Board of Directors of the Company, the Registration Statement and the Exhibits thereto, and such other documents as we deemed pertinent. We have also made such examination of law as we have felt necessary in order to render this opinion.

        As to certain factual matters relevant to this opinion, we have relied conclusively upon originals or copies, certified or otherwise identified to our satisfaction, of such records, agreements, documents and instruments, including certificates or comparable documents of officers of the Company and certificates of public officials, as we have deemed appropriate as a basis for the opinion hereinafter set forth. Except to the extent expressly set forth herein, we have made no independent investigation with regard to matters of fact, and we do not express any opinion as to matters of fact that might have been disclosed by independent verification. In rendering our opinion set forth below, we have assumed, without independent verification, (i) the genuineness of all signatures, (ii) the legal capacity of all natural persons, (iii) the authenticity of all documents submitted to us as originals, and (iv) the conformity to the original documents of all documents submitted to us as conformed, facsimile, photostatic or electronic copies.

        Based upon and subject to the foregoing, we are of the opinion that, upon the issuance of an appropriate order by the Commission allowing the Registration Statement to become effective and issuance of the Shares upon exercise of the Warrants in the manner described in the Registration Statement, the Shares will be legally issued, fully-paid and nonassessable.

        We are providing this opinion to you for your use in connection with the Registration Statement and the transactions contemplated by the Registration Statement, and this opinion may not be used or relied upon by any other person or for any other purpose without our express written consent, except that you may file a copy of this opinion with the Commission as an Exhibit to the Registration

Statement as described below. The only opinion rendered by us consists of those matters set forth in the preceding paragraph, and no opinion may be implied or inferred beyond the opinion expressly stated.

        We hereby consent that this opinion may be filed as an Exhibit to the Registration Statement and to the use of our name under the heading "Legal Matters" in the Prospectus.

Very truly yours,
DAVIS, MALM & D'AGOSTINE, P.C.
By:	/s/  C. MICHAEL MALM C. Michael Malm, Managing Director

CMM/JDC

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