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' Second Quarter 2004 Groundwater Report 8200 N Highway 99, Stockton, CA Page 5 of 6 ' electrical conductivity of the water were also measured during the development process Well MW12 was purged and sampled following Ground Zero's general field procedures described Previously in this report Groundwater samples were collected from wells MW12, MW15, and ' MW16 after the physical parameters stabilized and water levels in the wells recovered to near their pre-purged levels The samples were 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 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, if necessary ' Copies of field data sheets and purge logs are included in Attachment I A potentiometric surface map generated using the July 6, 2004 monitoring data is presented on ' Figure 5 Groundwater generally flowed to the northeast, although a cone of depression is evident around MW l, which serves as an extraction well Table 4 summarizes groundwater elevations in site monitoring wells ' No gasoline constituents were detected in the groundwater samples collected from wells MW 15 and MW 16 MW 12 contained no gasoline constituents except MTBE, which was detected at ' 140 ppb A copy of the laboratory report for water samples collected on July 6, 2004 is included in Attachment J Table 7 summarizes the analytical results of soil and groundwater samples collected from wells MW 15 and MW 16 The results from well MW12 have been included for comparison ' 5.0 SUMMARY The groundwater treatment system was put into operation on November 5, 2003 pursuant to WDR ' General Order No R5-2003-004412 The system generally operated continuously during the reporting period (April through June 2004) The average flow rate during the reporting period was approximately 0 8 gpm Approximately 100,149 gallons of water was treated during the reporting ' period A total of approximately 325,862 gallons of groundwater has been treated between November 2003 and June 28, 2004 During that period, approximately 57 pounds of petroleum hydrocarbons, including approximately 21 pounds of MTBE, were removed through the treatment ' system Groundwater in the shallow aquifer beneath the site generally flowed to the northeast when ' monitored on June 23, 2004, although a pumping depression was evident around the extraction well (MW1) �� jVN ' MTBE was not detected in downgradient A Zone well MW12 on June 23, 2004, unlike last SeC reporting period (March 17, 2004) where it was detected at relatively high levels However, MTBE was detected in MW12 on July 6, 2004 at 140 ppb No MTBE was detected in wells MW 10 or MW 11, located west of well MW 12, or in wells MW 15 and MW 16, which are located downgradient of well MW 12 I G 1GROUNBZEITULEBURG1Reports\QMR1200412QM2004 doe