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Y ERI 205513 SR19 'Posen Service Station 5886 Stockton CWiforma Janu 30 2002 . 2001 The GRI Fourth Quarter 20001 Groundwater Monitoring and Sampling Report is provided as Attachment A The results of the fourth quarter monitoring and sampling event indicate the following o Groundwater was measured at approximately 6 3 to 9 5 feet below ground surface(bgs) in the groundwater monitoring wells(an elevation increase of approximately 0 2 to 0 6 feet when compared to the third quarter 2001 groundwater monitoring and sampling event) During November 2001, groundwater flow direction was 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 3) o Total petroleum hydrocarbons as gasoline(TPHg), and benzene were not detected at concentrations at or above laboratory method detection limits in groundwater samples collected from the groundwater monitoring wells o MTBE was not detected at concentrations at or above laboratory method detection limits in groundwater samples collected from wells MWSD,MWSS, MW6S,MW7D/MW7S, MWBS/MWBI/MWBD,MW9S/MW9I/MW9D, and MWIOS/MW10D (Environmental Protection Agency[EPA] Method 8260) MTBE was detected in the remaining wells at concentrations ranging from 1 1 parts per billion(ppb)to 6,800 ppb using EPA Method 8260, detected concentrations ranged from 7 2 ppb to 5,800 ppb using EPA Method 8020 MTBE was not detected in wells MW4D,MW4S,and MW 10I using EPA Method 8020 o 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-dichloroetliane(1,2-DCA)and ethylene dibromide (EDB)were not detected at concentrations at or above laboratory method detection limits in the groundwater samples collected from the wells FIRST QUARTER 2002 ACTIVITIES The following activities are proposed to be completed during first quarter 2002 • ERI will install the remediation system microsparge wells • Tosco will continue weekly purging activities at the site using the UST cavity well and groundwater monitoring well MW3 as extraction wells until the proposed microsparge groundwater remediation system is constructed and started during first quarter 2002 The extracted groundwater will be transported to the Tosco refinery for disposal • Tosco will continue to collect monthly groundwater samples from wells MW1 through MW4S/D and wells MW6S/D for a period of 12 consecutive months to evaluate dissolved MTBE concentrations in groundwater beneath the site 4