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. EXECUTIVE SUMMARY Upgradient Environmental Consultants visited the Valley Motors dealership on August 14 to supervise the installation of groundwater monitor well VM-4 and again on August 18, 1998 to measure water depths and collect groundwater samples from the four on-site morutor wells Well VM-4 was drilled in March,but the borehole was left open with the permission of San Joaquin County Environmental Health Division(EHD)pending the County's review of the laboratory results of soil samples collected at that time By verbal communication in late July, Michael Infuma. of EHD authorized Upgradient to complete the boring as a well by installing screened PVC casing from 35 to 55 feet The well installation was performed by V & W Drilling and was witnessed by Mr Infurna. The depth to groundwater has decreased by more than six feet since the last monitoring in December 1997, and measurements indicate that groundwater continues to flow in an east-northeast direction The data indicate that the gradient is steeper in the northern part of the site near VM-4 than in the southern part of the site near VM-3 The difference appears to be related to the permeability of the water-beanng zone In the north, low-permeability clay near the ground surface forms a slight confining layer,causing the static water surface to be slightly deeper than in the southern part of the site After measuring the depth to groundwater in all four wells, 20 to 25 gallons of water were pumped from each well and contained in 55-gallon drums Water samples were then collected with disposable Teflon bailers, poured into 40-rn1 vials and 1-liter amber bottles, and preserved for laboratory analysis The samples were analyzed for TPH-gasoline and IPH-diesel using EPA method 602, for BTEX using EPA method 8020, and for five oxygenates using EPA method 8240B Gasoline and BTEX were detected to all four wells, including VM-3, in which very little contamination had been previously detected Since samples were last collected in December 1997, BTEX and TPH-g concentrations have risen significantly in all wells,particularly VM-2, which is the closest well to the point of the unauthorized release (the gasoline dispenser) The gasoline and BTEX data suggest that groundwater has become more contaminated since the early 1998 rise in the static water level into the zone of residual soil contamination, and that contaminants have begun to migrate to the east At this time, no gasoline oxygenates have been detected, but the high concentrations of gasoline required the laboratory to dilute the samples, thereby elevating the detection limits for oxygenates In accordance with previous communications regarding the analysis for chlorinated hydrocarbons, the water samples were not analyzed for these contaminants It is presumed that the concentrations of these compounds continue to exceed regulatory limits Due to the evidence of increasing and migrating groundwater contamination, we cannot recommend site closure at this time Rather, we recommend that steps be taken to collect the data that are needed to complete a Problem Assessment Report so that regulatory agencies can evaluate the site and determine what, if any, remediation might be needed 1