Groundwater Plume Characteristics at Small Chlorinated-Solvent Release Sites in California

Abstract

There is a need to study the spatiotemporal distribution of chlorinated solvent releases in groundwater to understand the risk/threat they pose to human health, water quality, and the environment, which then can be used to prioritize clean-up and evaluate regulatory closure with appropriate risk management controls. This paper provides a statistical analysis of spatiotemporal distribution of perchloroethylene (PCE) (and its degradation products including trichloroethene [TCE]) from eighty-three cases across California for which data were available onthe State Water Resources Control Board’s GeoTracker database and the Department of Toxic Substance Control Board’s Envirostor database. These cases consisted of seventy-one dry cleaning sites and twelve other similar small solvent release sites. Statistical analyses of available groundwater data were performed to estimate: maximum concentrations at the source area, groundwater plume length, plume stability; and correlations between plume length, concentrations, and plume age. At 90% of the sites, the PCE and TCE plume lengths were less than 1,569 feet (478 meters) and 1,782 feet (543 meters), respectively. The average plume lengths for PCE and TCE were 670 feet (204 meters) and 701 feet (213 meters), respectively. At 90% of the sites that have reached stable conditions, PCE and TCE concentrations at the source areas were less than 2,670 and 660 micrograms per liter (µg/L) respectively. This study for the first time provides key characteristics of small chlorinated-solvent plume behaviors in California that can be used to prioritize management of small chlorinated-solvent release sites and to develop strategies towards achieving closure at these sites.