A Phase III Environmental Site Assessment is performed following the identification of a release of hazardous substances at a property and builds upon the information gathered in a Phase II report to delineate the extent of contamination. The Phase III, also known as a Remedial Investigation/Feasibility Study, normally involves an assessment of alternative cleanup methods, costs, and logistics. The resulting report details a remedial plan to perform site cleanup and the follow-up for monitoring any residual contaminants.