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EXECUTIVE SUMMARY <br /> • Groundwater samples were collected from four monitor wells and one domestic well at the Gillies <br /> Trucking yard at 3931 Newton Road on January 2, 2003 One well could not be located, one well <br /> was dry, and another could not be sampled because the purge pump became lodged in the hole and <br /> could not be removed The pump remains dammed in this well, and a work plan to drill out the <br /> casing and destroy the well has been submitted to San Joaquin County Environmental Health <br /> Department <br /> The depth to groundwater was approximately 62 feet in most wells, which places it below the depth <br /> of the Modesto channel aquifer, within the underlying silt and clay of the Modesto aquitard For this <br /> reason, purge water was very muddy and all wells pumped poorly and were slow to recharge The <br /> water level was below the bottom of well GT-10, which is screened from 45-60 feet within the <br /> channel and upper half of the aquitard <br /> The water elevation data were contoured to yield a map of the piezometric surface The elevation <br /> contours form a relatively planar pattern trending east-west The water table slopes northward at a <br /> gradient of approximately 0 0045 ft/ft <br /> The water samples were analyzed for TPH-diesel, which was detected in three samples at <br /> concentrations of 57, 60, and 530 parts per billion The first two of these are only slightly above the <br /> detection limit of 50 ppb, indicating that groundwater contamination at the depth of the Modesto <br /> • aquitard zone (40-65 feet) is close to or Iess than the diesel detection limit in three of the four <br /> sampled monitor wells Diesel was also not detected in the Gillies domestic well <br /> • ` 1 <br />