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MApy <br /> STOCKTON FORMER" MANUFACTXECUTIVE URED GAS SuM SITE <br /> • PNAs were detected in HydropunchT <br /> and Zone A from MW-14 d samples collected from Zones <br /> located upgradient of the site,s S the drilling of those Zone C and B in MW-15 <br /> in the ro suggesting that there may grad These wells are <br /> groundwater. y be upgradient sources of PNAs <br /> • Concentrations of PNAs have continued to decrease in Zones <br /> Some of the lowest concentrations to date were detected during' <br /> sampling A, B,and C since 1992. <br /> P g event(March and April 1996). <br /> g the most recent <br /> • Concentrations of volatile organic compounds (VOCs) and total <br /> hydrocarbons (TPH)have decreased over <br /> near former undergroundtime in the Zone A petroleum <br /> storage tanks(IJSTs . monitoring wells located <br /> e <br /> ave not <br /> Zone A monitoring wells. The extent of benzene has b en defin defined as beneath AedtIer <br /> Within the PG&E site in Zones A, B,and C. <br /> • As determined by a risk assessment,there is no current risk from COPCs in <br /> groundwater as no complete exposure pathways exist. soil or <br /> After approval of the Phase IV Groundwater Investigation report by the Department of <br /> Toxic Substances Control(DTSC), the feasibility study(FS) will be prepared to recommend <br /> a site-specific soil and groundwater remedy. A draft soil operable unit FS was submitted to <br /> DISC and the Regional Water Quality Control Board (RWQCB) on November 8, 1995. <br /> PG&E recommends that the following steps be taken with respect to groundwater at the <br /> Stockton site: <br /> • Finalize this Phase IV Groundwater Investigation report. <br /> • Continue to monitor PNAs, BTEX, and TPH in all Zone A, B, and C wells while the FS is <br /> being prepared and finalized. <br /> • Implement the remedy that will be recommended in the Final FS and described in the <br /> Remedial Action Plan (RAP). <br /> • Monitor groundwater concentrations of PNAs, BTEX,and TPH in Zone A, B,and C <br /> wells for at least 8 quarters to evaluate the effectiveness of the remedy. <br /> ES-2 <br /> G.-WROM 107161841003.000 <br />