Phase I Environmental Site Assessment (ESA)

A Phase I Environmental Site Assessment (ESA) is an investigation conducted to identify potential or existing environmental contamination on a property. Governed by ASTM Standard E1527-21, Phase I ESAs are a critical step in commercial real estate transactions, providing buyers with protection under CERCLA's innocent landowner defense.

The assessment includes a review of historical records, aerial photographs, topographic maps, regulatory databases, and a physical site inspection. For properties with current or former USTs, the Phase I ESA will examine UST registration records, compliance history, and any documented releases. The presence of USTs or former UST sites is one of the most common recognized environmental conditions (RECs) identified.

If a Phase I ESA identifies potential contamination concerns, a Phase II ESA involving soil and groundwater sampling may be recommended. Properties near LUST release sites or with historical UST use are more likely to require Phase II investigation. Environmental professionals use UST Map and similar databases to research UST and LUST records as part of the Phase I process.