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v o A S S O C I A T E S I N C prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southeast The average hydraulic gradient on June 11, 2003 was calculated to be 0 007 ft/ft or approximately 37 ft/mile A summary of groundwater monitoring data is presented in Table 1 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 1 1, 2001 This workplan was approved by SJCEHD with minor modifications A total of approximately 0 43 gallons of free product has been recovered from the skimmer in well MW2 since installation On June 11 and July 11, 2003 an immeasurable sheen was observed in well MW2 Table 3 summarizes the product thickness measurements and volume of product removed through the end of the second quarter of 2003 FILTRATION SYSTEM In May 2002, a carbon filtration system was installed to remove petroleum hydrocarbons from the water in domestic well DW On April 4, April 30 and June11, 2003, water samples were collected from the first and second effluent ports identified as ICC Effluent and 2CC Effluent in the filtration system On April 4, 2003, benzene was detected in the 1 CC Effluent sample at 3 2 ppb On June 11, 2003, TPHg and benzene were detected from the ICC Effluent sample at 250 and 11 ppb, respectively All other constituents were reported as not detected On June 11, 2003, ads° influent water samples collected from DW contained 12,000 ppb of TPHg and 910 ppb of @'1°o benzene MTBE and fuel oxygenates were not detected, nor have they been detected in water Nz.-"- 1'-1 samples collected from well DW for the past 12 consecutive quarters J1 \tj As soon as data was available, ATC resampled ICC and 2CC Effluent in July 2003 When analytical results are available, the carbon vessels will be replaced if hydrocarbons are present 0- July sampling will be summarized in the third quarter 2003 report It appears the filtration system is effective in removing petroleum products from water from well DW Analytical results are summarized in Table 2 CONCLUSIONS Concentrations from wells MW 1 through MW 10, and DW remain consistent with the results from the previous sampling event The direction of groundwater flow was consistent with the previous monitoring event Groundwater elevations have increased since March 2003 S\EnviromentahI63931REPORTS12gr-2003 doc 4