EPA may redefine 'begin actual construction' to expedite projects

The U.S. EPA has announced its intent to propose a rule revising the regulatory definition of “begin actual construction” under the Clean Air Act New Source Review (NSR) program to allow certain non-emitting, ancillary construction before an NSR permit; a proposed rule is expected in January 2026 with a final rule targeted for September 2026.

• Main action: The EPA will propose a rule to clarify “begin actual construction,” allowing developers to undertake core-and-shell and other non-emitting site work (e.g., concrete pads, external walls) prior to issuance of an NSR permit; the agency cites AI-driven energy demand and data center expansion as a motivating factor and reaffirmed 2020 draft guidance in a September 2025 letter to Maricopa County regarding TSMC’s Phoenix semiconductor facility. The proposed rule is expected by January 2026 with a final rule targeted for September 2026.
• Background & caveats: The EPA previously interpreted the term broadly (the 1986 Reich memo), but the 2020 draft guidance concluded earlier limits were “unnecessarily restrictive” and the revised interpretation “better conforms to the regulatory text.” The EPA cautioned pre-permit construction proceeds at developers’ “own risk” and warned that time and resources expended on pre-permit construction may not be used to justify issuance of a permit; state permitting agencies retain broad discretion and effects will vary by project and jurisdiction.