Phase I Environmental Site Assessments are necessary as part of the due diligence process. A lender or a conservative investor may require the completion prior to closing on a property.  The objective of a Phase I ESA is to estimate the potential for the property under investigation to contain substantial levels of contaminants that could occur in the soil, surface water, and/or groundwater, and which may have resulted from activities either on the subject site or from nearby off-site sources.