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' Fourth Quarter 2004 Groundwater Report 8200 N Highway 99, Stockton, CA Page 2 of 6 ' on the air stripper It was discovered that the air stripper's effluent pump failed On December 23, 2004, the system was brought back online by bypassing the air stripper and pumping the water directly through the carbon units after authorization was received by the Regional Board to ' temporarily bypass the air stripper The system operated in this fashion until January 18, 2004, when the effluent pump was repaired ' Approximately 188,475 gallons of water was treated during the reporting period (October 20 through December 30, 2004) at an average rate of 19 gpm A total of approximately 554,973 gallons of groundwater were treated between November 2003 and December 30, 2004 During that ' period, approximately 76 pounds of petroleum hydrocarbons, including approximately 23 pounds of MTBE, were removed through groundwater extraction and treatment No carcinogenic polynuclear aromatic hydrocarbons (PAHs) have been detected in any influent or effluent samples ' collected at the site In addition, the concentrations of inorganic constituents analyzed as part of WDRs issued for the site are well below regulatory levels ' Treatment system flow data and maintenance notes through December 30, 2004 are summarized in Table 1 Analytical results of samples collected from the treatment system through December 30, 2004 are summarized in Table 2 The estimated mass removal is summarized in Table 3 ' Treatment system monitoring logs and laboratory reports are included in Attachments A and B, respectively 3.0 QUARTERLY SITE WORK 3 1 Groundwater Elevation Measurements A Ground Zero technician monitored water levels in all site wells, and collected groundwater samples from monitoring wells MW 1 through MW 16, the vapor extraction well V W 1, and the groundwater extraction well EW2 on December 14, 15 and 16, 2004 The depth to groundwater was measured in each well on December 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 68 74 to 70 25 feet The depth to water in groundwater extraction wells were measured at 75 20 feet btoc in well EW1 and 82 62 feet btoc in well EW2 Groundwater elevations in A Zone monitoring wells ranged ' from 36 49 to 37 37 feet below mean sea level (MSL) The measured groundwater elevations in extraction wells on December 14, 2004 were 44 12 feet below MSL in EW1 and 53 58 feet below MSL in well EW2, which represent drawdown of approximately 7 and 16 feet, respectively Groundwater levels in the A Zone wells, not including the pumping wells MW 1 and EW2, rose an average of 2 12 feet between September 14, 2004 and December 14, 2004 The groundwater level in B Zone wells MW9B and MW 14B measured 68 46 feet btoc and 69 24 feet btoc, respectively Groundwater elevations in the B Zone wells MW9B and MW 14B were 11GZA_FSIVOL_11DATAIGROUNDZEITULEBURGIReports\QMR1200414QM2004 doc