SITE INFORMATION AND CORRESPONDENCE_1998-2000

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INFORMATION SHEET SETTLING DRY CLEANING DEFENDANTS LINCOLN VILLAGE CENTER GROUNDWATER TREATMENT SYSTEM SAN JOAQUIN COUNTY The Settling Dry Cleaning Defendants, as defined by Consent Decree (and listed in Attachment A to the permit), proposes to discharge waste from a groundwater treatment system designed to remove volatile organic compounds (VOCs) from groundwater and investigation derived residual fluids collected during ongoing investigation, remediation, and monitoring activities. The groundwater treatment system is designed to treat 300 gpm (430,000 gpd) of extracted groundwater, and residual fluids collected during ongoing investigation, remediation, and monitoring activities. About 200 gpm (290,000 gpd) will be discharged to a storm drain in the City of Stockton, tributary to Fourteen Mile Slough, and then the San Joaquin River. Pumped groundwater will be treated by passing it through an air stripper, and then passing it serially through two exchangeable activated carbon units prior to being discharged to the storm drain. The activated carbon units are regenerated or disposed off-site. Tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene (DCE), methylene chloride, and 1,2-dichloroethane (1,2-DCA) have been identified in the groundwater as constituents of concern. In addition, it is suspected that the constituents benzene, toluene, xylene, and ethylbenzene (BTEX), lead, and also methyl tertiary-butyl ether (MTBE) or other oxygenate compounds may become present in water pumped from extraction wells due to two fuel contamination sites which are also present at the Lincoln Center. The proposed treatment plant is expected to treat the volatile organic compounds to non-detectable levels. It is currently unknown if the treatment plant will effectively remove oxygenate compounds. This Order requires a treatment performance evaluation to show the effluent limitations can be met, and also ongoing monitoring for constituents of concern. Effluent limitations have been set as follows: a) 30 Day median concentrations are set at a practical quantitation limit (PQL) of 0.5 µg/l for all VOCs and BTEX constituents. A `median' is used rather than an `average' to allow for the detection of a constituent in individual samples without automatically causing violation of the monthly limitation. The 30-day average concentration for lead is established at 5 µg/1, one-tenth the MCL for lead. The 30-day average concentration MTBE is established at 35 4g/1, the State of California Drinking Water Action Level.