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u ERI 205513 QSR23 76 Facility 5886,Stockton,Caltfortua January 30,20D3 • Gettler-Ryan, Inc (GRI) of Dublin, California, under direct contract to ConocoPhillips performed quarterly groundwater monitoring and sampling at the site on November 20 and 21, 2002 The GRI Fourth Quarter Event of November 20 and 21, 2002, Groundwater Monitoring and Sampling Report(GRI,December 26,2002) is provided as Attachment A The results of the fourth quarter monitoring and sampling event indicate the following • Groundwater was measured at approximately 6 1 to 9 3 feet below ground surface(bgs)in the groundwater monitoring wells During November 2002, groundwater flow direction remained towards the southwest with a calculated hydraulic gradient ranging from approximately 0 002 to 0 005 Historical groundwater flow directions are shown on the Groundwater Flow Direction Rose Diagram(Plate 4) 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, however, laboratory reporting lirnits were elevated for samples collected from wells MW1,MW2,and MW3 • MTBE was not detected at concentrations at or above laboratory method reporting linuts in groundwater samples collected from wells MW5D/MW5S through MW7D/MW7S, MW8S/1, MW9S/I/D and MW10S MTBE was detected in wells MW1 through MW4S/D,MW81), and MW 10I/D at concentrations ranging from 2 3 parts per billion(ppb)to 5,300 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,however, laboratory reporting limits were elevated for samples collected from wells MWI,MW2, and MW3 FIRST QUARTER 2003 ACTIVITIES The following activities are proposed to be completed during first quarter 2003 ERi will continue to perform 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 ConocoPhillips will continue to perform quarterly groundwater monitoring and sampling at the subject site The water samples will be submitted to a California state-certified laboratory for analysis • ConocoPhillips and ERI will continue to conduct 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