This document provides an overview of environmental due diligence services provided by GLE Associates, Inc., a consulting firm formed in 1989. It describes the Phase I, Phase II, and Phase III environmental site assessment processes defined by ASTM standards to identify potential environmental risks and contaminants at a site. A Phase I assessment involves records review, site visits, and interviews to identify recognized environmental conditions. Phase II involves sampling if a Phase I finds potential issues, while Phase III determines the extent of contamination to estimate cleanup costs. The document is intended to educate clients on environmental due diligence and GLE Associates' expertise in this area.