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W ERI 205513 QSR25 76 Facility 5886 Stockton California Jul 22 2003 i (GRI, June 13, 2003) is provided as Attachment A The results of the second quarter monitoring and sampling event indicate the following • Groundwater was measured at approximately 5 40 to 8 30 feet below ground surface (bgs) in the groundwater monitoring wells During May 2003, groundwater flow direction remained towards the southwest with a calculated hydraulic gradient ranging from approximately 0 003 to 0 007 Historical groundwater flow directions are shown on the Groundwater Flow Direction Rose Diagram(Plate 4) • Wells MW5S/D, MW7S/D,MW8S/I, and MW9S/I/D are sampled semi-annually(first and third quarters)and were not sampled during the second quarter 2003 groundwater monitoring and sampling event • Total petroleum hydrocarbons as gasoline(TPHg), and benzene were not detected at concentrations at or above laboratory method reporting limits in groundwater samples collected from the groundwater monitoring wells MWI through MW3, MW4S/D, MW6S/D,MW813, and MW l OS/I/D, however, laboratory reporting limits were elevated for samples collected from well MW 1 • MTBE was not detected at concentrations at or above laboratory method reporting limits in groundwater samples collected from wells MW4D,MW6S/D, MW8D, and MW 1 OS/D MTBE was detected in wells MW 1 through MW3, MW4S, and MW 101 at concentrations ranging from 5 3 parts per billion (ppb)to 2,700 ppb using EPA Method 8260B • Oxygenated compounds including ethanol, tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether(ETBE), and tertiary amyl methyl ether(TAME), and lead scavengers including 1,2-dichloroethane(1,2-DCA)and ethylene dibromide(EDB) were not detected at concentrations at or above laboratory method reporting limits in the groundwater samples collected from the wells MW1 through MW3, MW4S/D, MW6S/D, MW8D and MW 10S/UD, however, laboratory reporting limits were elevated for samples collected from well MW 1 THIRD QUARTER 2003 ACTIVITIES The following activities are proposed to be completed during third quarter 2003 • Continuation of monthly O&M at the site and collect monthly groundwater samples from wells MW 1 through MW3 to evaluate the effectiveness of the microsparge remediation system and the extent of dissolved TPHg, benzene, toluene, ethyl benzene, total xylenes (BTEX), and MTBE concentrations in groundwater beneath the site • Continuation of quarterly groundwater monitoring and sampling at the subject site The water samples will be submitted to a California state-certified laboratory for analysis • Continuation of a comprehensive review of the data acquired during previous work The results will be presented to the County in quarterly reports,which describe the status of the proposed work by the dates established by the County 4