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detected in the upstream surface water sample (DDN) collected from the drainage ditch located east of the site
<br /> None of the other BTEX constituents or TPH-G were detected at or above the laboratory reported detection
<br /> limits in this sample BTEX and TPH-G were not detected in any of the three remaining surface water samples
<br /> MTBE was detected at or above the laboratory reported detection limit in all of the surface water samples except
<br /> the sample collected from the vicinity of the pump house in the island drainage channel (IDCW) None of the
<br /> remaining selected gasoline oxygenates/additives were detected at or above the laboratory reported detection
<br /> Iimits in any of the surface water samples
<br />' MTBE (20 µg/1) was the only analyte detected at or above the laboratory reported detection limits in the marina's
<br /> pre-treated drinking water Only chloroform, bromodiehloromethane, and dibromochloromethane were detected
<br /> in the marina's treated drinking water at or above the laboratory reported detection limits (at concentrations of
<br />' 18, 6 1, and 3 0 µg/1, respectively) Chloroform, bromodichlorom ethane, and dibromochloromethane appear to
<br /> be byproducts of the marina's drinking water treatment system
<br />' On December 30, 1998, Condor conducted quarterly groundwater and surface water monitoring at Herman &
<br /> Helen's Marina located at Venice Island Ferry in Stockton, California Laboratory analytical results indicated
<br /> that the gasoline oxygenate MTBE was detected in samples collected from monitor wells MW-1, MW-2, MW-3,
<br /> and MW-4 at concentrations of 1 3 µg/1, 11,000 pg/l, 3,500 µg/l, and 1 5 µg/I, respectively Tertiary-butanol was
<br /> detected in the groundwater samples collected from monitor wells MW-2 and MW-3 at concentrations of 150
<br /> µg/1 and 130 µg11, respectively TAME was detected in the groundwater samples collected from monitor wells
<br /> 1 MW-2 and MW-3 at concentrations of 37 µg/1 and 8 3 µg11, respectively None of the other oxygenates/additives
<br /> were detected at or above the laboratory reported detection limits in any of the groundwater samples
<br /> Toluene was detected in the groundwater sample collected from monitor well MW-2 at a concentration of 1 2
<br /> pg/1 BTEX constituents were detected in the groundwater sample collected from monitor well MW-4 at
<br /> concentrations of 24 µg11, 0 4 µg/1, 2 3 pg/l, and 22 µg11, respectively BTEX constituents were not detected in
<br /> the groundwater samples collected from monitor wells MW-1 and MW-3 TPH-G was detected in the
<br /> groundwater sample collected from monitor well MW-4 at a concentration of 0 2 mg/1 TPH-G was not detected
<br /> in the groundwater sampILS collected from monitor wells MW-1, MW-2, or MW-3
<br /> Intrinsic bioremediation testing was discontinued at the site following the third quarter, 1998, monitoring event
<br /> because of inconclusive results and because the petroleum hydrocarbon contamination at the site is probably of
<br />' secondary concern relative to the presence of gasoline oxygenates The intrinsic bioremediation testing results
<br /> for the four quarters beginning with the fourth quarter, 1997, groundwater monitoring event and ending with the
<br /> third quarter, 1998, groundwater monitoring event, indicated that subsurface conditions at the site appeared to be
<br /> conducive to the aerobic and/or anaerobic breakdown of petroleum hydrocarbons However, the results did not
<br /> conclusively indicate that intrinsic bioremediation was occurring at the site No well-defined differences in the
<br /> intrinsic bioremediation parameters were established up-gradient (MW-1), in the plume center (MW-4), and
<br />' down-gradient (MW-2 and MW-3) at the site This may be in part related to the relatively low concentrations of
<br /> petroleum hydrocarbons present at MW-4 and the very short residence time of groundwater in the soil at the site
<br />' Groundwater elevation measurements collected at the site on December 30, 1998, indicated that the average
<br /> depth to groundwater was approximately 4 6 feet bgs which is approximately one-half foot higher than the
<br /> average groundwater elevation measured on September 30, 1998 Groundwater elevation contours for December
<br />' 30, 1998, indicated that the groundwater gradient at the site was generally consistent with that measured on
<br /> September 18, 1997, December 31, 1997, March 27, 1998,June 26, 1998, and September 30, 1998
<br /> BTEX and TPH-G were not detected at or above the laboratory reported detection limits in any of the surface
<br /> water samples Low concentrations of MTBE (1 4 and 1 0 pg/i) were detected in the upstream surface water
<br /> sample (DDN) and the downstream surface water sample (DDS), respectively None of the remaining selected
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