Phase I is a historical property research. Depending on the property, sometimes a transaction screen is sufficient.
Phase II is environmental testing of a property which may include soil, groundwater, vapor, sediments, asbestos, lead-paint or other hazardous materials including PCBs.
Phase III is remediation of a problem identified in a Phase I or a Phase II which could be through removal, risk evaluation and/or in-situ remediation.

Phase I Environmental Site Assessment (ESA)
A Phase I property site assessment is a due diligence procedure that both buyers and sellers conduct to identify past and present environmental liabilities. A Phase I can prevent future litigation over a real estate transaction by openly disclosing environmental issues.

A Phase I ESA is meant to identify the potential for impacts by hazardous or toxic materials and to identify other possible environmental constraints on the site. No environmental sampling or analysis is conducted under the Phase I scope of work (unless specifically requested or part of a more specific guideline). The form and content of an ESA will follow the form and content as outlined in ASTM standard E 1527-13. The results of the Phase I ESA will be used to evaluate whether or not further study (such as a Phase II ESA) is warranted. To obtain and develop the information required for the Phase I ESA of a property in a timely and efficient manner, the following scope of work is typically conducted as indicated by the availability, relevancy, and adequacy of the background information, and by the environmental consultant's best field judgment.

The Phase I is a property assessment that includes a walkover of the property and associated structures; a review of historic property information including maps, aerial photographs, deeds, telephone or address directories, etc.; a review of potentially impacted properties in the vicinity; a summary of knowledgeable party information and review of prior reports; and the review of local, State and Federal files pertaining to the property address.

Items evaluated in the Phase I report include: tanks, drains, pits, spills, in-ground and aboveground equipment, petroleum and chemical use, and environmental liens. Additional issues which may be included in the Phase I at the lenders or clients request include: wetlands, radon, asbestos, lead-based paint, and drinking water. The Phase I report is typically research only. Unless otherwise specified as part of the scope of work, testing or surveys are outside of the typical Phase I requirements.