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� VM EL <br /> a <br /> 1 <br /> A S S d C I A T E S i N C <br /> CONCLUSIONS <br /> ' Groundwater flow direction and gradient is generally consistent with previous sampling events <br /> Water table elevations have generally decreased since monitoring was initiated at the site in 1999 <br /> Benzene was not detected at or above the laboratory detection Iimit of 0 5 pg/L for the first time in <br /> quarterly groundwater monitoring samples collected from MW1 Benzene has not been detected at or <br /> above the laboratory detection limit of 0 5 pg/L in groundwater samples collected from MW2 and <br /> MW3 since March 2003 and September 2002, respectively Groundwater analytical results associated <br /> ' with MW2 and MW3 remained within historical parameters as set by previous groundwater <br /> analytical results The interim remedial action conducted from July 8 to December 4, 2003, may have <br /> helped to reduce petroleum hydrocarbon concentrations in the vicinity of MW l as evidenced by the <br /> ' lack of detectable concentrations of benzene in the groundwater sample collected from MW1 during <br /> the quarterly groundwater monitoring event on December 8, 2003 <br /> ' RECOMMENDATIONS <br /> Based on the results of the fourth quarter 2003 monitoring event, we recommend one additional <br /> quarterly groundwater monitoring event be conducted to verify the reduction of the benzene <br /> concentration in the groundwater sample collected from MW1 If a reduction in concentration is <br /> indicated, we recommend the site be considered for closure <br /> Please contact our office at(209) 579-2221 if you have any questions or comments <br /> ' Respectfully submitted, <br /> ATC Associates Inc <br /> /n� <br /> Todd Hafn <br /> er Jetnne <br /> Hornsey, P E <br /> ' Project Geologist CA Registered Civil Engineer No 47410 <br /> ' cc Mr Paul Van Dyken, Sr, N & S Irrigation <br /> Jim Barton, RWQCB � <br /> r � <br /> ' r <br /> Attachments <br /> i r � <br /> f CHI <br /> s <br /> slenvironmentaRl498RReportsl4QR-03 doe 4 <br /> MEL-- <br /> - — — — <br />