Basic Elements of Phase I and Phase II Environmental Site Assessments

Environmental Site Assessments (ESAs) have been developed to evaluate environmental issues at any site previously used for commercial purposes. ESAs generally are performed in two stages, Phase I and Phase II, with remediation following if deemed necessary following the completion of both phases. Standards for the Phase I and Phase II ESAs have been established by the American Society for Testing and Materials (ASTM) to address the “All-Appropriate-Inquiry” (AAI) aspect to the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).


Phase I Environmental Site Assessments (ASTM E1527-13) typically consist of four tasks:

  1. Gathering information about past and present uses of the site;
  2. Inspection of the site by an environmental professional, usually accompanied by someone familiar with the property;
  3. Reviewing environmental files maintained by the site owner and regulatory agencies;
  4. Preparing a report that identifies existing and potential sources of contamination on the property.

The result of a Phase I ESA determines the need for further site investigation, i.e., the need for any type of environmental sampling and analysis or may indicate that further investigation is not warranted.


Phase II Environmental Site Assessments (ASTM E1903-11) focus on gathering specific information as required about the property and can include the following tasks:

  • Surface and subsurface soil sampling, groundwater and surface water sampling, soil vapor sampling (along with laboratory analysis), sediment sampling, collection of plant or aquatic species samples;
  • Above/underground storage tank content and tightness testing, asbestos containing material (ACM) sampling, PCB sampling and identification, geomagnetic or geophysical surveys;
  • Directly measuring conditions such as noise levels or radiation;
  • Using environmental fate or transportation models to evaluate the potential migration of the contamination.

The result of a Phase II ESA is the determination of the need for a work plan for cleanup and may also allow the determination of whether conditions or events at the site are causing or likely to cause adverse effects and will require notification to the appropriate regulatory authority.