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v o • A S S O C I A T E S I N C were elevated due to dilution The groundwater sample collected from on-site supply well DW contained detectable concentrations of TPHg and BTEX, but contained no detectable concentrations of oxygenate fuel additives ' Analytical results of groundwater samples are summarized in Table 2 f Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 FREE PRODUCT REMOVAL Floating petroleum product has previously been observed in well MW2 On January 18, 2002, ATC installed a passive skimmer system in well MW2 in accordance with ATC's Workplan for Drinking Water Well Replacement, Temporary Water Source, and Free Product Skimmer Installation at Pacific Coast Recreation, 3755 Munford Avenue, Stockton, California, dated October 11, 2001 This workplan was approved by SJCEHD with minor modifications Approximately 0 36 gallons of free product has been recovered from the skimmer in well MW2 On July 31, 2002, approximately 0 08 feet of free product was observed in well MW2 On August 29, 2002, approximately 0 01 feet of free product was observed in well MW2 On September 24, 2002, approximately 0 01 feet of free product was observed in well MW2 Table 3 summarizes the product thickness measurements and volume of product removed through the end of the third quarter of 2002 FILTRATION SYSTEM In May 2002, a carbon filtration system was installed to remove petroleum hydrocarbons from the water in domestic well DW The carbon filtration system consists of two liquid-phase carbon canisters connected in series Extracted groundwater passes directly through the canisters The influent sample is collected from the sample port prior to the canisters The ICC effluent sample is collected from the port between the canisters The 2CC effluent sample is collected from the port after the second canister Influent water samples collected from DW on September 24, 2002 contained 82,000 ppb of TPHg. and 7,300 ppb of benzene Fuel oxygenates including MTBE were not detected in water samples collected from well DW, although detection limits were elevated due to dilution factors ' Benzene was detected at 4 0 ppb on July 31, and 2 7 ppb on August 29 in the water samples collected from the effluent sampling port identified as ICC Effluent TPHg, BTEX, and fuel oxygenates were not detected in water samples collected on September 24 from the I CC effluent sampling port TPHg, BTEX, and fuel oxygenates were not detected in water samples collected on August 29 and September 24 from the 2CC effluent sampling port It appears the filtration system is effective in removing petroleum products from water from well DW Analytical results are summarized in Table 2 � w 1163931quwt1yl3gr-2002 doc 4