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' Fourth Quarter 2004 Groundwater Report
<br /> 8200 N Highway 99, Stockton, CA
<br /> Page 4 of 6
<br />' xylenes at 1,400 ppb
<br /> MTBE was present in wells EW 1, EW2, MW2, MW3, MW4, MW5, MW6, MW 12, MW13C, and
<br />' VW1 at concentrations of 1,900 ppb, 59 ppb, 420 ppb, 600 ppb, 4,000 ppb, 44 ppb, 540 ppb, 350
<br /> ppb, 45 ppb, and 26,000 ppb, respectively No MTBE was detected in samples collected from
<br /> wells MW7, MWS, MW913, MW10, MW11, MW1413, MW15, or MW16
<br />' Table 5 summarizes groundwater analytical results Figures 4, 5 and 6 present isoconcentration
<br /> maps of TPHg, benzene, and MTBE in the A Zone, respectively, from December 2004
<br />' Attachment D contains laboratory reports and chain-of-custody documentation for groundwater
<br /> samples collected from site wells in December 2004 Attachment E contains graphs of TPHg,
<br /> benzene, and MTBE concentrations of over time in all site wells
<br />' 3.3 Domestic Well Sampling and Analysis
<br />' As directed by EHD in a letter dated October 10, 2003, Ground Zero collected water samples from
<br /> eight nearby domestic wells, including the site facility well The samples were collected from
<br /> either a sample port at the wellhead or from the nearest available sampling location (i e garden
<br />' hose) Samples were collected after the pump was turned on for approximately 15 minutes The
<br /> samples were immediately stored in an ice chest refrigerated to a temperature of approximately 4°C
<br /> and delivered under chain of custody protocol to FGL Laboratories (FLAP #1563) and analyzed for
<br /> volatile organic constituents utilizing EPA Method 524 2
<br /> No VOCs were detected in any of the samples collected from the nearby domestic wells Copies of
<br /> the laboratory reports were submitted to the respective property owner The Iaboratory reports for
<br /> samples collected from the nearby domestic wells are included in Attachment F Figure 7 shows
<br /> the locations of the domestic wells relative to the site
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<br /> 4.0 SUMMARY
<br />' The groundwater treatment system was put into operation on November 5, 2003 pursuant to WDR
<br /> General Order No R5-2003-004412 The system was idle between October 1 and October 20,
<br />' 2004 while the extraction well pump was being repaired The system generally operated
<br /> continuously between October 20, 2004 and December 30, 2004, with brief periods of non-
<br /> operation due to maintenance The second extraction well (EW2) was incorporated into the system
<br />' in late November One of the 2,000-pound GAC units was replaced in mid-December with virgin
<br /> carbon In mid-December the air stripper's effluent pump burned out The extracted groundwater
<br />' was diverted to bypass the air stripper and the system operated with only the carbon units for the
<br /> remainder of December When in operation during the reporting period, the average flow rate
<br /> through the treatment system was approximately 19 gallons per minute (gpm) Approximately
<br /> 188,475 gallons of water was treated during the reporting period A total of approximately 554,973
<br /> gallons of groundwater has been treated between November 2003 and December 30, 2004 During
<br /> that period, approximately 76 pounds of petroleum hydrocarbons, including approximately 23
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