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Third Quarter 2004 Groundwater Report 8200 N Highway 99, Stockton, CA Page 2of6 k i ' operated continuously between September 1 and September 23, 2004 when the extraction pump failed The extraction pump was replaced on October 19, 2004 and the treatment system returned to service on October 20, 2004 ' Approximately 40,636 gallons of water was treated dunng the reporting period (July 1 through September 30, 2004) A total of approximately 366,498 gallons of groundwater were treated ' between November 2003 and September 24, 2004 During that period, approximately 67 pounds of petroleum hydrocarbons, including approximately 22 pounds of MTBE, were removed through the treatment system Treatment system flow data and maintenance notes through September 30, 2004 ' are summarized in Table 1 Analytical results of samples collected from the treatment system through September 30, 2004 are summanzed 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 ADDITIONAL DRILLING ACTIVITIES On July 20, 2004, Ground Zero personnel supervised the drilling and installation of the ' groundwater monitoring/groundwater extraction well EW2 The well was completed to a depth of approximately 85 feet below ground surface (bgs) The well was completed of 4-mch diameter, schedule 40 FVC casing The lowermost 20 feet of PVC casing installed in the well is slotted screen (0 01-inch slot size) The filter pack consists of #2/12 pre-washed, Monterey silica sand from the bottom of the well to approximately 2 feet above the slotted interval The annular seal consists of two feet of hydrated bentonite pellets at the top of the filter pack, then neat cement grout ' to the ground surface A locking well cap was placed on the well and a protective well monument was cemented into place The well was installed by V&W Drilling, Inc (C57-720904) under the supervision of a Ground Zero geologist Copies of the boring/well log are included in Attachment ' C Well locations including the new well EW2 can be seen on Figure 2 Soil samples were collected at 5-foot intervals for soil characterization and possible analysis Soil ' encountered in the vadose zone (0-70 feet bgs) consisted primarily of clay and silt with thin lenses of silty sand (-28-32 feet bgs) and poorly graded sand (-38-48 feet bgs) Groundwater was encountered at approximately 70 feet during drilling, but rose to approximately 66 9 feet bgs in the ' borehole The saturated zone in EW2 (70-85 feet bgs) consisted primarily of silt and sand, although a sandy fat clay was encountered at the bottom of the borehole Soil samples collected at depths of approximately 65 feet bgs (capillary fringe), 80 feet bgs, and 85 feet bgs (bottom of the hole) were ' submitted to Argon Laboratories for analysis of gasoline constituents MTBE was the only constituent of concern detected in the soil samples collected from EW2 It was ' detected in samples EW2-80 and EW2-85 at concentrations of 0 27 parts per million (ppm) and 0 022 ppm No analytes were detected in the sample collected at 60 feet bgs Table 6 summarizes the analytical results of soil samples collected from well EW2 Copies of laboratory results are included in Attachment D 1 ' 0 IGROUNDZEITULEBURG\ReportslQMR000413QM2004 doe