CLH: Other company developments

Item 8.01. Other Events. On September 17, 2026 , Clean Harbors, Inc. (the “Company”) issued a press release announcing that it had commenced a private offering of senior notes due 2034 to persons reasonably believed to be “qualified institutional buyers” in the United States, as defined in Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”), and to certain non-U.S. persons outside the United States in offshore transactions pursuant to Regulation S under the Securities Act. On September 17, 2026 , the Company issued a press release announcing the pricing of its previously announced offering of 6.250% senior notes due 2034 (the “Notes”). Copies of the press releases are attached as Exhibit 99.1 and 99.2 to this Current Report on Form 8-K and are incorporated by reference into this Item 8.01. Neither this Current Report on Form 8-K nor the press releases constitute an offer to sell, or the solicitation of an offer to buy, the Notes. Item 9.01. Financial Statements and Exhibits. (d) Exhibits Exhibit Number Description 99.1 Press release of the Company relating to the announcement of the offering, dated September 17, 2026 99.2 Press release of the Company relating to the pricing of the offering, dated September 17, 2026 104 Cover Page Interactive Data File (embedded within the Inline XBRL document) 1 SIGNATURES Pursuant to the requirements of the Securities and Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Clean Harbors, Inc. (Registrant) September 18, 2026 /s/ Eric J. Dugas Executive Vice President and Chief Financial Officer 2