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v o A S S O C I A T E S I ISI C 2004 An additional 500 gallons of stored water was pumped through the on-site activated carbon filtration system and surfaced discharged on March 25, 2004 Water samples of the discharged water were collected during each pumping event and contained no detectable concentrations of petroleum hydrocarbons These samples were identified as PT DWSW-2 and PT DWSW-1-3, respectively The discharge was done under the supervision of the SJEHD and at a rate slow enough to ensure no runoff to the storm drainage system occurred A complete report of the pump test is discussed in ATC's Summary Report ofAddttional Subsurface Investigation, Pacific Coast Recreation, 3755 Munford Avenue, Stockton, California, to be submitted under separate cover CONCLUSIONS Concentrations from wells MW1 through MW10 remain generally consistent with the results from the previous sampling event The direction of groundwater flow continues to be variable across the site, with a general northerly gradient Slight groundwater mounding has occurred around well MW3 Groundwater elevations have increased since December 2003 RECOMMENDATIONS Based on the results of the first quarter 2004 monitoring episode, we recommend the following • Conduct the second quarter 2004 groundwater monitoring and sampling of wells MWI through MW 10 and DW and analyze samples for TPHg, BTEX, and MTBE by EPA method 8015B / 8021B Inspect well box conditions and maintain all well boxes in a water tight state • Request MTBE only be screened by EPA method 8020, and if positive, confirm with EPA method 8260B Because the previous eight (8) quarters results have consistently contained no detectable concentrations of ETBE, DIPE, TBA, TAME, 1,2-DCA, and EDB, ATC requests to discontinue analyzing groundwater samples by 8260 except for MTBE confirmation analysis as described above 1 • Continue to monitor ICC and 2CC Effluents on a monthly basis If hydrocarbons are Vm detected m either of the 1 CC or 2CC Effluents, the carbon w111 be replaced The Influent is the same as sample DW The Influent does not require monthly sampling, so it is sampled during quarterly monitoring events • ATC recommends sampling the three domestic wells across Munford Street to the south of the site This has been done on two prior occasions at approximately one-year intervals, and it has been approximately one year since the last off-site sampling event • S\Enviromenta11163931REPORTSII qr-2004 doc 5