Phase I Environmental Site Assessments (Phase I ESA) are governed by the American Society for Testing & Materials (ASTM)E1527 – Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process (ESA)” and in late 2021, an updated version, ASTM E 1527-21 was released, offering further clarifications, updated terminology, and additional examples since the prior version, ASTM E1527-13.

To meet the requirements of due diligence for liability protection under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the Environmental Protection Agency’s (EPA) All Appropriate Inquiry (AAI) sets the standards for innocent landowners, contiguous property owners and bona fide prospective purchasers.

Since the issuance of ASTM 1527-21, Leaaf has been conducting all Phase I ESAs to comply with both ASTM 1527-13 & 1527-21 and meet the requirements of the AAI Rule. However, on December 15, 2022, the EPA amended AAI and now requires the use of ASTM E1527-21, with an effective date of February 13, 2023, replacing ASTM E1527-13.

For further information regarding the EPA’s AAI Rule and its requirements, please visit EPA’s website at or reach out to Leaaf’s expert staff.