X0202 SCHEDULE 13G/A 0000902664-26-001042 0001747057 XXXXXXXX LIVE 1 Common Stock, par value $0.01 per share 03/31/2026 0000822818 Clean Harbors Inc. 184496107 42 LONGWATER DRIVE, P.O. BOX 9149 NORWELL MA 02061-9149 Rule 13d-1(b) D1 Capital Partners L.P. DE 0.00 1338281.00 0.00 1338281.00 1338281.00 N 2.5 IA PN Daniel Sundheim X1 0.00 1338281.00 0.00 1338281.00 1338281.00 N 2.5 HC IN Clean Harbors Inc. 42 Longwater Drive, PO Box 9149, Norwell, MA 02061-9149. This statement is filed by D1 Capital Partners L.P. (the "Investment Manager") and Daniel Sundheim (the "Mr. Sundheim"). The foregoing persons are hereinafter sometimes referred to as the "Reporting Persons." The Investment Manager is a registered investment adviser and serves as the investment manager of private investment vehicles and accounts, including D1 Capital Partners Master LP (the "Investment Vehicle"), and may be deemed to beneficially own the shares of common stock, par value $0.01 per share (the "Common Stock") of Clean Harbors Inc. (the "Company") held by the Investment Vehicle and/or its subsidiary. Mr. Sundheim indirectly controls the Investment Manager and may be deemed to beneficially own the shares of Common Stock issuable held by the Investment Vehicle and/or its subsidiary. The filing of this statement should not be construed as an admission that any Reporting Person is, for the purposes of Section 13 of the Securities Exchange Act of 1934, as amended, the beneficial owner of the securities reported herein. D1 Capital Partners L.P. 9 West 57th Street, 36th Floor New York, New York 10019 Daniel Sundheim c/o D1 Capital Partners L.P. 9 West 57th Street, 36th Floor New York, New York 10019 Investment Manager - Delaware Mr. Sundheim - United States of America N IA HC The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 52,910,946 shares of Common Stock reported to be outstanding as of February 11, 2026, as reported in the Company's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission on February 18, 2026. 2.5% The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference. N Y N See item 2(a). The Investment Vehicle (and/or its subsidiary) has the right to receive and the power to direct the receipt of dividends from, and the proceeds from the sale of, the shares of Common Stock reported herein. Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. D1 Capital Partners L.P. /s/ Amanda Hector 05/15/2026 Daniel Sundheim /s/ Daniel Sundheim 05/15/2026