CLH: Material agreement · New financial obligation · Other company developments

Item 1.01. Entry into a Material Definitive Agreement. Issuance of 6.250% Senior Notes due 2034 On October 1, 2026, Clean Harbors, Inc. (the “Company”), issued $600.0 million aggregate principal amount of 6.250% senior notes due 2034 (the “Notes”). The Company utilized $470 million of the net proceeds from the offering of Notes to finance the purchase price of the Company’s previously announced acquisition of EnviroServe, a national provider of environmental and waste management services (the “EnviroServe Acquisition”), and the intends to use the remainder of the net proceeds to repay the borrowings under its revolving credit facility that were incurred to partially finance the purchase price of the Company’s previously announced acquisition of ES&H (the “ES&H Acquisition”). The ES&H Acquisition closed on September 18, 2026 and the EnviroServe Acquisition closed on October 2, 2026. The Notes have not been registered under the Securities Act of 1933, as amended (the “Securities Act”), or the securities laws of any other jurisdiction, and may not be offered or sold in the United States absent registration or an applicable exemption from the registration requirements of the Securities Act. The Notes were offered only to persons reasonably believed to be qualified institutional buyers in accordance with Rule 144A under the Securities Act and outside the United States to non-U.S. persons in accordance with Regulation S under the Securities Act. Indenture The Notes were issued under an Indenture, dated October 1, 2026 (the “Indenture”), among the Company, substantially all of the Company’s domestic subsidiaries, as guarantors, and U.S. Bank Trust Company, National Association, as trustee. The Indenture provides, among other things, that the Notes will be senior unsecured obli