CLH: Other company developments

Item 8.01 Other Events. On May 14, 2026, Clean Harbors, Inc. issued a press release announcing the completion of its acquisition of Terra Nova Solutions. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. Item 9.01 Financial Statements and Exhibits. (d) Exhibits Exhibit Number Description 99.1 Press Release dated May 14, 2026 104 The cover page to this Current Report on Form 8-K, formatted in iXBRL (Inline eXtensible Business Reporting Language) 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) May 14, 2026 /s/ Eric J. Dugas Executive Vice President and Chief Financial Officer 2