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<br />' detected in the upstream surface water sample (DDN) collected from the drainage ditch located cast of the site
<br /> . None of the other BTLX constituents or 1 PH--G were detected at or above the laboratory reported detection
<br /> limits in this sample BTEX and TPH-[r were not detected in any of the three remaining surface water samples
<br />' M f BE was detected at or above the laboratory reported detection lima in all of the surface water samples except
<br /> the sample collected from the vicinity of the pump 110USL in the island drainage channel (IDC'W) None of the
<br /> remaining selected gasoline oxygenates/additives were detected at or above the laboratory reported detection
<br />' limits in any of the surface water samples
<br /> MTB1 (20 µg/l) was the only analyte detected at or above the laboratory reported detection limits in the marina's
<br />' pre-treated drinking water Only chloroform, bromodichloromethane, 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 lug/l, respectively) Chloroform, bromodichloromcthane, 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 4g/l, 3,500 µg/l, and 1 5 µg/l, 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/l and 130 µg/l, respectively TAME, was detected in the groundwater samples collected from monitor wells
<br /> MW-2 and MW-3 at concentrations of 37 µg/I and 8 3 µg/l, 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 /> liegg/l BTEX constituents were detected in the groundwater sample collected from monitor well MW-4 at
<br /> concentrations of 24 pg/l, 0 4 µg/1, 2 3 µg/l, and 22 µg/1, 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 samples 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 /> I 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 /> Iintrinsic 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 /> I 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 geneially consistent with that measured on
<br /> September 18, 1997, December 31, 1997, March 27, 1998, June 26, 1998, and September 30, 1998
<br /> Ile
<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 µg/1) 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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