Clean Harbors Closes Equity Offering of 2.3 Million Shares of Common Stock.

BRAINTREE, Mass. -- Clean Harbors, Inc. ("Clean Harbors") (NASDAQ: CLHB), the leading provider of environmental and hazardous waste management services throughout North America, today announced that it has closed its public offering of 2.3 million shares of its common stock, which included 300,000 shares of common stock issued upon exercise by the underwriters of their over-allotment option. After deducting the underwriting discount and offering expenses, the Company received net proceeds of approximately $60.3 million from the offering. Following the closing, common shares outstanding total approximately 19.4 million.

The Company will use net proceeds from the offering to redeem $52.5 million, or 35%, of Clean Harbors' outstanding 11.25% senior secured notes due 2012 and pay the prepayment penalty and accrued interest relating to the redemption. That redemption will be completed in January 2006. Following the redemption, the annual rate on the Company's $50 million secured synthetic letter of credit facility, which was announced on December 1, 2005, will be reduced from 3.10% to 2.85%.

The offering was lead managed by Credit Suisse First Boston. Needham & Company, LLC and Wedbush Morgan Securities acted as co-managers.

A registration statement relating to the common stock offering was filed with the Securities and Exchange Commission and was declared effective on December 7, 2005. Copies of the prospectus may be obtained by visiting the SEC's website at www.sec.gov or by contacting Credit Suisse First Boston, One Madison Avenue, Prospectus Department, New York, New York 10010-3629 (Telephone number: 212-325-2580). This announcement shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of the common stock in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

About Clean Harbors, Inc.

Clean Harbors, Inc. is North America's leading provider of environmental and hazardous waste management services. With an unmatched infrastructure of 48 waste management facilities, including nine landfills, five incineration locations and seven wastewater treatment centers, the Company provides essential services to over 45,000 customers, including more than 175 Fortune 500 companies, thousands of smaller private entities and numerous federal, state and local governmental agencies. Headquartered in Braintree, Massachusetts, Clean Harbors has more than 100 locations strategically positioned throughout North America in 36 U.S. states, six Canadian provinces, Mexico and Puerto Rico. For more information, visit www.cleanharbors.com.

Safe Harbor Statement

Any statements contained herein that are not historical facts are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, and involve risks and uncertainties. These forward-looking statements are generally identifiable by use of the words "believes," "expects," "intends," "anticipates," "plans to," "estimates," "projects," or similar expressions. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those reflected in these forward-looking statements. Readers are cautioned not to place undue reliance on these forward-looking statements, which reflect management's opinions only as of the date hereof. The Company undertakes no obligation to revise or publicly release the results of any revision to these forward-looking statements. Furthermore, all financial information in this press release is unaudited, and may change materially upon completion of the audit of the Company's financial statements. A variety of factors beyond the control of the Company affect the Company's performance, including, but not limited to:

--The effects of general economic conditions in the United States, Canada and other territories and countries where the Company does business;

--The effect of economic forces and competition in specific marketplaces where the Company competes;

--The possible impact of new regulations or laws pertaining to all activities of the Company's operations;

--The outcome of litigation or threatened litigation or regulatory actions;

--The effect of commodity pricing on overall revenues and profitability;

--Possible fluctuations in quarterly or annual results or adverse impacts on the Company's results caused by the adoption of new accounting standards or interpretations or regulatory rules and regulations;

--The effect of weather conditions or other aspects of the forces of nature on field or facility operations;

--The effects of industry trends in the environmental services and waste handling marketplace;

--The effects of conditions in the financial services industry on the availability of capital and financing;

--The Company's ability to manage the significant environmental liabilities, which it assumed in connection with the CSD acquisition; and

--The availability and costs of liability insurance and financial assurance required by governmental entities relating to our facilities.

Any of the above factors and numerous others not listed nor foreseen may adversely impact the Company's financial performance. Additional information on the potential factors that could affect the Company's actual results of operations is included in its filings with the Securities and Exchange Commission, and its subsequent reports on Form 10-Q, which are filed with the SEC and the Annual Report on Form 10-K/A for the fiscal year ended December 31, 2004, which the Company filed on April 29, 2005, and subsequent quarterly and/or other reports filed with the SEC since then, which may be viewed on the Investor portal of the Company's Web Page at www.cleanharbors.com.