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Happy Valentine’s Day! It’s Official - New ASTM E1527-21 Phase I ESA Standard Adopted!

Prepared by Managing Principal Mark Shifflett and Supervising Environmental Scientist Heather Fields

As of February 14, 2024, the most recent ASTM Phase I standard (E1527-21) has been adopted as the new industry standard for Phase I ESAs. Reports prepared under the previous standard (ASTM E1527-13) will no longer satisfy the requirements for conducting All Appropriate Inquiries (AAI) for landowner liability protections under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).

Key changes under E1527-21 include:


1.       New changes

  • Historical Research for Adjoining Properties – The “Big 4” are required to be included - aerial photographs, fire insurance maps, city directories, and topographic maps – and they should be used to evaluate both the subject property and adjoining/adjacent properties.

  • Lien Search to 1980 – Lien and Activity Use Limitation (AUL) searches need to be conducted on all property owners on the chain of title back to 1980.

2.       Improved clarification for the definition of already required elements

  • Recognized Environmental Conditions (RECs) – The definition has been expanded to further emphasize the definition of a “likely presence” of a REC as something which can be expected or believed based on logic, experience, or available evidence.

  • Controlled Recognized Environmental Conditions (CRECs) – CRECs should be compared against current regulatory standards to determine if onsite conditions still meet the current standards.

  • Historic Recognized Environmental Conditions (HRECs) – HRECs should be evaluated against any new potential exposure pathways since closure.

  • Significant Data Gaps – The significance of any data gap identified must be specified and an opinion should be provided regarding the need for additional information.

  • Shelf Life – The shelf life of a Phase I ESA is based on individual task completion dates during its preparation, each of which have their own 180-day limit. These include the date of the site inspection, receipt of historical records, and receipt of database records.

3.       Emerging Contaminants

  • If a compound is not identified as a hazardous substance under CERCLA, it is not currently included in the scope of the standard, but it is recommended that emerging contaminants of concern be considered as a non-scope item similar to asbestos, mold, or lead-based paint. It should be discussed with the User if relevant to the site, but it is not required to be included in the Phase I ESA report. The primary emerging contaminant of concern today is the group of chemicals known as per- and poly-fluoroalkyl substances (PFAS).

  • Once an emerging contaminant is defined as a hazardous substance under CERCLA, these substances must be evaluated within the scope of E1527-21.


While most of the E1527-21 updates are not hugely different from the prior E1527-13 standard, they do provide improved definitions and examples to help clarify what qualifies as a REC and what is needed to be compliant with AAI. Waterstone implemented the E1527-21 standard in 2021, ensuring our Phase I ESA reports meet all new requirements. Now everyone will be required to do so for all future due diligence studies.


If you have questions regarding the changes to the E1527-21 standard, please don’t hesitate to reach out to Mark, Heather or our Phase I Environmental Professional staff for guidance.

Waterstone Office: 714-414-1122




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