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rp 14r <br /> ERI 205513 QSR17 Tosco Service Station 5886 Stockton Ca[iforrua Iul 23 2001 <br /> • <br /> • Total petroleum hydrocarbons as gasoline (TPHg) and benzene were not detected at <br /> concentrations at or above laboratory method detection limits in groundwater samples <br /> collected from the groundwater monitoring wells <br /> • Diesel-range hydrocarbons were not detected at concentrations at or above laboratory <br /> method detection limits in groundwater samples collected from the groundwater monitoring <br /> wells However, laboratory detection limits were elevated for groundwater samples <br /> collected from the wells <br /> MTBE was not detected at concentrations at or above laboratory method detection Iimits in <br /> t,\ groundwater samples collected from wells MW41) MWSD, MWSS, MW7D/MW7S, <br /> rT' v MW8S/MW81, MW9S/MW9I/MW9D, and MW10S/MW101/MW10D (EPA Method <br /> 8260) MTBE was detected in the remaining wells at concentrations ranging from 3 25 ppb <br /> to 11,700 ppb using EPA Method 8260 (ranging from 16 2 ppb to 10,400 ppb using EPA <br /> Q Method 8020) MTBE was not detected in wells MW4S and MWBD usinEPA Method <br /> 8020 g <br /> • Oxygenated compounds ethanol, tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), <br /> ethyl tertiary butyl ether (ETRE), and tertiary amyl methyl ether (TAME), and lead <br /> scavengers 1,2-dichloroethane (1,2-DCA) and ethylene dibromide (EDB) were not detected <br /> at concentrations at or above laboratory method detection limits in the groundwater samples <br /> • collected from the wells However, laboratory detection limits were elevated for <br /> groundwater samples collected from wells MW1 through MW3 <br /> THIRD QUARTER 2001 ACTIVITIES <br /> The following activities are proposed to be completed during third quarter 2001 <br /> • Tosco will continue weekly purging activities at the site utilizing the UST cavity well and <br /> groundwater monitoring well MW3 as extraction wells The extracted groundwater will be <br /> transported to the Tosco refinery for disposal <br /> • Tosco will continue to collect monthly groundwater samples from wells MW1 through MW4S/D <br /> and wells MW6S/D for a period of 12 consecutive months to evaluate dissolved MTBE <br /> concentrations in groundwater beneath the site <br /> • Tosca will seal surface cracks on the site to reduce the possibility of surface hydrocarbon spills <br /> impacting soil <br /> • TRC will provide the results of the enhanced leak detection test of the underground storage <br /> systems <br /> • 4 <br />