PUMP-AND-TREAT ACCOMPLISHMENTS - A REVIEW OF THE EFFECTIVENESS OF GROUND-WATER REMEDIATION IN SANTA-CLARA VALLEY, CALIFORNIA

Pump and treat has been successful in significantly reducing the volatile organic contaminant concentrations in ground water in Santa Clara Valley, California. The California Regional Water Quality Control Board, San Francisco Bay Region, currently oversees 61 sites in Santa Clara Valley with operating pump-and-treat systems, of which 42 sites have been extracting ground water since at least 1987. This review evaluates the effects of ground water extraction on contaminant concentrations at 37 of those 42 sites. The evaluation focuses on trichloroethane, trichloroethene, and dichloroethane, as these were the most prevalent contaminants encountered at the sites. The majority of sites obtained greater than 90 percent reduction in maximum concentrations for one or more of the three contaminants. While only one of the 37 sites obtained maximum contaminant levels (MCL) for all contaminants, six of the sites included in the analyses reached MCLs for one or more of the sampled contaminants, and an additional seven of the sites are near MCLs for at least one contaminant. Our findings indicate that, while pump and treat successfully reduced maximum concentrations at most of the sites reviewed, successful attempts to reduce maximum contaminant concentrations to below MCLs are limited.