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j 1 1.0 INTRODUCTION . GHH Engineering, Inc. (GW is currently providing USA Gasoline Corporation(USA) ' professional environmental services to conduct groundwater monitoring at their retail gasoline station#110 located at 2132 East Mariposa Road, Stockton, California., as shown on Figures 1, 2 and 3. Mr. Srikanth Dasappa of USA authorized GHH to prepare the Second Quarter, 2001, ' Groundwater Monitoring Report(QMR) for the site. This report has been prepared for submittal to the San Joaquin County, Environmental Health Division(County), the lead regulatory agency overseeing environmental issues at the site. The County Site Code is 41669. ' 1.1 Scope of Work Groundwater monitoring was conducted at the site on April 30, 2001. The following is a brief summary of the scope of work authorized by USA: i • Locate and measure depths to groundwater in wells MW-1P through MW-6P, MW i and MW-2. ' Purge a minimum of three equivalent well volumes of groundwater from each of the wells and monitor pH, temperature and conductivity. • Collect groundwater samples from the monitoring wells. ' Analyze water samples for total petroleum hydrocarbons in the gasoline range (TPH G), benzene, toluene, ethylbenzene, and xylenes(BTEX); 1,2-dichloroethane (1,2-DCA);and the oxygenated fuel additives methyl-tert-butyl-ether (MTBE), di-isopropyl ether(RIPE), ' ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), and tertiary butyl alcohol(TBA)using EPA Methods 8015 Modified, 8020 and 8260B, respectively. ' Prepare this QMR for submittal to USA and the appropriate regulatory agencies. ' 2.0 GROUNDWATER MONITORING The following section discusses field protocol used during data collection for this QMR. ' 2.1 Groundwater Elevations ' Prior to gauging depths to groundwater, the eight groundwater monitoring wells were checked for the presence of free floating hydrocarbon compounds using an interface probe. No free product was present in any of the wells. Depths to groundwater measurements were then taken ' from each well from surveyed marks on the casing using an electric water level sensor. Calculated groundwater elevations are summarized in Table 1, and shown on Figure 4. ' 2.2 Monitoring Well Purging The monitoring wells were purged using a 2-inch diameter, submersible Rediflo groundwater ' pump or disposable bailer,until a minimum of three equivalent well volumes of water were removed from each well. Groundwater purged from the wells was placed into Department of Transportation approved 55-gallon drums and stored on-site prior to disposal by USA.