An enhanced preliminary assessment of Jefferson Proving Ground was performed to characterize the environmental impacts of actions occurring at the property, and to provide a basis for the development of remedial actions. Characterization was performed through examination of site activities, determination of the quantity of hazardous substances present, and evacuation of the potential pathways for contamination migration which would affect public health and the environment. Thirty-six solid waste management units and sixteen other areas requiring environmental evaluation were investigated. Recommendations for additional studies, sampling, and actions are contained in the summary. Actions include delineation of the actual limits of several waste disposal sites; installation of ground water monitoring wells; sampling of soils, surface and ground water; location of waste disposal areas; location of unexploded ordnance; and surveying of buildings for radon, asbestos, and lead paint.