ADVANCED DRAINAGE SYSTEMS, INC.

Item 1.01 Entry Into a Material Definitive Agreement. On October 1, 2026, Advanced Drainage Systems, Inc. and its subsidiary, ADS Investment LLC, a Delaware limited liability company, (together, the “Company”) entered into a Securities Purchase Agreement (the “Purchase Agreement”) with StormTrap Investors, L.L.C., a Delaware limited liability company, as representative of the sellers, and certain sellers as set forth in the Purchase Agreement (together, the “Sellers”), pursuant to which the Company will acquire StormTrap Investments, L.L.C. (“StormTrap”), an industry leader in large volume, space-constrained, highly engineered stormwater solutions. The Sellers have agreed to sell to the Company all the outstanding equity interests of StormTrap Investments, L.L.C. and its direct subsidiaries for approximately $530 million, or approximately $450 million when adjusted for the present value of the expected tax benefits, subject to certain purchase price adjustments. The transaction will be funded by a combination of cash on hand and funds from the existing credit facility of the Company. The Purchase Agreement contains customary representations, warranties and covenants from the Sellers. The Company has obtained a representations and warranties insurance policy that will provide a source of recourse in the event of any breaches of the representations and warranties of the Sellers contained in the Purchase Agreement, subject to a retention amount, exclusions, policy limits and certain other terms and conditions. The closing of the transaction remains subject to customary closing conditions, including customary covenants regarding the parties’ efforts to obtain required antitrust approvals. A copy of the Purchase Agreement is attached as Exhibit 2.1 to this Current Report on Form 8-K and is incorporated herein by reference. The foregoing description of the Purchase Agreement does not purport to be complete and is qualified in its entirety by reference to the Purchase Agreement. The representations, warranties and covenants set forth in the Purchase Agreement have been made only for the purposes of that agreement and solely for the benefit of the parties to the Purchase Agreement, may be subject to limitations agreed upon by the contracting parties, including being qualified by confidential disclosures made for the purposes of allocating contractual risk between the parties to the Purchase Agreement instead of establishing these matters as facts, and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to investors. Investors should not rely on the representations, warranties and covenants or any description thereof as characterizations of the actual state of facts or condition of any party to the Purchase Agreement or any of their respective subsidiaries, affiliates or businesses.

Item 7.01 Regulation FD Disclosure. On October 5, 2026, the Company issued a press release announcing the proposed acquisition of StormTrap. A copy of the Company’s press release is attached hereto as Exhibit 99.1 and hereby incorporated by reference. The information furnished pursuant to this Item 7.01, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Exchange Act or otherwise subject to the liabilities under Section 18 of the Exchange Act and shall not be deemed to be incorporated by reference into any filing of the Company under the Securities Act of 1933 or the Exchange Act.