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' Third Quarter 2004 Groundwater Report 8200 N Highway 99, Stockton, CA Page 3 of 6 ' The newly installed well was developed and sampled on August 3, 2004 Fieldwork consisted of developing, purging and sampling well EW2 The technician developed the newly installed well until the turbidity of the water was visibly reduced, generally to a turbidity measurement of less ' than 50 NTU The temperature, pH and electrical conductivity of the water were also measured during the development process A groundwater sample was collected after the physical parameters stabilized and the water level in the well recovered to near its pre-purged level The ' sample was temporarily stored in an ice chest refrigerated to a temperature of approximately 4°C and delivered under chain of custody protocol to Argon Laboratories (FLAP #2359) for analysis Purged groundwater was temporarily contained in appropriately labeled DOT-approved 55- gallon drums in accordance with 49 CFR part 172 and 40 CFR part 262, and will eventually be processed through the groundwater treatment system Copies of field data sheets and purge logs are included in Attachment E ' The water sample collected from EW2 contained no gasoline constituents except MTBE, which was detected at 400 ppb A copy of the laboratory report for the water sample collected on ' August 3, 2004 is included in Attachment F Table 5 summarizes the analytical results of the groundwater sample collected from EW2 ' 4.0 QUARTERLY SITE WORK 4.1 Groundwater Elevation Measurements A Ground Zero technician monitored water levels in all site wells, and collected groundwater ' samples from monitoring wells MW2 through MW16 and the groundwater extraction well EW2 on September 14, 15 and 16, 2004 ' The depth to groundwater was measured in each well on September 14, 2004 prior to any purging Groundwater elevations were calculated by subtracting the measured depth to water from the respective well head elevation The measured depth to groundwater below the tops of ' the well casings (btoc) in the A Zone monitoring wells ranged from 70 91 feet in well MW2 to 75 24 feet in well MW1 Groundwater elevations in the A Zone ranged from 38 83 feet below mean sea level (MSL) in well MW2 to 44 16 feet below MSL in well MW1, which serves as the ' extraction well for the treatment system Groundwater levels in the A Zone wells, not including pumping well MW1, fell an average of 2 55 feet between June 23, 2004 and September 14, 2004 ' The groundwater level in B Zone wells MW9B and MW 14B measured 70 85 feet btoc and 71 65 feet btoc, respectively Groundwater elevations in the B Zone wells MW9B and MW 14B were calculated to be 39 26 feet below MSL and 39 42 feet below MSL, respectively Groundwater ' elevations the B Zone wells fell an average of 2 46 feet between June 23, 2004 and September 14, 2004 The groundwater elevation in C Zone well MW 13C was measured at 73 00 feet btoc (40 82 feet below MSL), a decrease of 2 06 feet between June 23, 2004 and September 14, 2004 Groundwater in the A Zone aquifer on September 14, 2004 generally flowed in a northeasterly direction, although a cone of depression is evident around the extraction well The groundwater ' G 1GROUNDZEITULEBURGIRepor,slQMR1200413QM2004 doc