| Item 1. | |
| (a) | Name of issuer:
Clean Harbors Inc. |
| (b) | Address of issuer's principal executive offices:
42 Longwater Drive, PO Box 9149, Norwell, MA 02061-9149. |
| Item 2. | |
| (a) | Name of person filing:
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. |
| (b) | Address or principal business office or, if none, residence:
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 |
| (c) | Citizenship:
Investment Manager - Delaware
Mr. Sundheim - United States of America |
| (d) | Title of class of securities:
Common Stock, par value $0.01 per share |
| (e) | CUSIP No.:
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| Item 3. | If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: |
| (a) |  Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
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| (b) | Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
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| (c) | Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
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| (d) | Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
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| (e) |  An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
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| (f) | An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
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| (g) | A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
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| (h) | A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
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| (i) | A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
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| (j) | A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
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| (k) | Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
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| Item 4. | Ownership |
| (a) | Amount beneficially owned:
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. |
| (b) | Percent of class:
2.5% |
| (c) | Number of shares as to which the person has:
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| | (i) Sole power to vote or to direct the vote:
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.
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| | (ii) Shared power to vote or to direct the vote:
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.
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| | (iii) Sole power to dispose or to direct the disposition of:
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.
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| | (iv) Shared power to dispose or to direct the disposition of:
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.
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| Item 5. | Ownership of 5 Percent or Less of a Class. |
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Ownership of 5 percent or less of a class
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| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. |
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If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
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. |
| Item 7. | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. |
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Not Applicable
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| Item 8. | Identification and Classification of Members of the Group. |
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Not Applicable
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| Item 9. | Notice of Dissolution of Group. |
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Not Applicable
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