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30 FIELD SERVICES AND LABORATORY ANALYSIS Geocon performed groundwater monitoring and sampling on April 8, 2004 to determine water table elevation and the distribution of dissolved hydrocarbons in groundwater monitoring wells 1 Groundwater elevation data and contaminant concentrations in groundwater are reported in Table 1 Thiee offsite domestic wells were sampled to determine if potable water supplied to adjacent residents are impacted with petroleum hydrocarbons One onsite domestic well (DW-1) has nitrate concentrations that exceed drinking water standards A replacement well (DW-IR) for DW-1 was constructed in February 2004 As of the date of this report the service from well DW-1 has not been switched to DW-1 R lin accordance with a verbal directive from Mike Infurna of San Joaquin County Environmental Health, sampling of well DW-1 has ceased Operation and maintenance (O&M) services were performed for the SVE and ozone sparge systems for the reporting period between January 10, 2004 and April 8, 2004 31 Water Table Elevations And Gradient On April 8, 2004, Geocon personnel measured the depth to water in each of the ten Site-related groundwater monitoring wells A water level indicator was used to gauge the wells to the nearest 0 01 foot A groundwater elevation contour map indicates that groundwater flow was generally toward the south at a gradient of 0 002 ft/ft as depicted in Figure 4 Groundwater monitoring data is presented in Table 1 32 Quarterly Groundwater Sampling Groundwater monitoring wells were purged using a submersible pump until pH, temperatuie, and ' conductivity readings had stabilized Temperature, conductivity, and pH readings were recorded for each well for each casing volurne removed using a field rnstiurnent Water purged from the wells is stoied in a 500-gallon above ground storage tank within the remediation system compound 1 Domestic wells DW-2R, DW-3, and DW-4 were purged by opening a spiget at the well head works, draining the well's holding tank, and allowing the tank to re-fill with fresh water pumped from the aquifer Once the tank had been recharged, water samples were collected duectly from a spigot at the holding tank Domestic wells DW-2R, DW-3, and DW-4 are on a quarterly sampling schedule Adequate recoveiy was observed in the purged groundwater monitoring wells prior to sampling A ' disposable bailer was used to collect the groundwater samples All samples were decanted fiorn the bailer into the appropriate containers, preserved with ice, and transported under chain-of-custody protocol to Advanced Technology Laboratory (ATL) in Signal Hill, California for the organic chemical analysis i i Prolu,t No 58643-06-01 -5- luty 1,2004