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<br /> Analytical Results
<br /> Data from the March 2000 sampling event indicate that the groundwater beneath the Disco
<br /> {. site contains detectable levels of total petroleum hydrocarbons (TPH) as gasoline, BTEX
<br /> compounds (benzene,toluene,ethyl benzene and total xylenes), 1,2-Dichloroethane
<br /> (1,2-DCA), 1,2-Dibromoethane,also known as ethylene dibromide (EDB), and tert-butanol
<br /> (TBA). Analytical results are presented in Tables 4 and 5. Table 4 presents groundwater
<br /> sample analysis for TPH-gasoline and benzene, toluene,ethyl benzene,and xylenes (BTEX).
<br /> Table 5 presents analytical results for MTBE and other oxygenate compounds. Table 6
<br /> presents analytical results for 1,2-DCA and EDB. The results are summarized below,
<br /> dependent upon the location of the well in relation to the plume: upgradient,cross-gradient,
<br /> i or within the plume.
<br /> The original groundwater sampling event occurred on March 28 and 29,2000. Due to
<br /> laboratory oversight,groundwater samples collected on March 28 and 29,2000 were not
<br /> analyzed for EDB and 1,2-DCA. Inspection of the chromatographs indicated that EDB and
<br /> or 1,2-DCA were detected in monitoring wells MW-DIS-1,NP-1-70,-80,and—90,and
<br /> SVE-South,however,concentrations could not be quantified. Therefore, those monitoring
<br /> wells were resampled on May 5,2000 and analyzed for oxygenates, 1,2-DCA and EDB.
<br /> Upgradient Wells- MW-DIS-5, -6,-7S,-71),-8S,and-8D.
<br /> All upgradient wells were sampled and analyzed for oxygenates, 1,2-DCA and EDB during
<br /> this sampling event.There were no detections of these compounds in these wells.
<br /> Cross-gradient Wells- MW-DIS-3,-9,and—10.
<br /> All crossgradient wells were sampled and analyzed for oxygenates, 1,2-DCA,and EDB
<br /> during this sampling event. Due to an oversight, MW-DIS-3 and MW-DIS-9 were also
<br /> analyzed for TPH as gasoline and BTEX compounds. Benzene was detected in MW-DIS-3 at
<br /> a concentration of 0.38 4g/L. This is the first detection of benzene in this well since June
<br /> 1995. Because this detection was anomalous,MW-DIS-3 was resampled on May 25,2000 to
<br /> confirm this detection. Benzene was not detected in the subsequent sample.
<br /> Wells Within the Plume- MW-DIS-1, MW-DIS-2, NP-1-70', NP-1-80', NP-1-90', SVE-South and
<br /> SVE-North
<br /> j TPH as gasoline and BTEX compounds were detected in groundwater samples collected
<br /> from monitoring wells MW-DIS-1,MW-DIS-2,NP-1-70',NP-1-80',NP-1-90',SVE-South and
<br /> SVE-North. The concentrations detected in these wells are consistent with previous
<br /> sampling events (see Table 4). Concentrations continue to decline in MW-DIS-2.
<br /> Petroleum hydrocarbon concentrations detected in MW-DIS-1 during this monitoring event
<br /> were lower than November 1999 results,and were similar to the July 1999 sampling event.
<br /> TPH as gasoline was detected in MW-DIS-1 at a concentration of 7,500 pg/L and benzene,
<br /> toluene,ethylbenzene,and total xylenes were detected concentrations of 1,400,920,200,and
<br /> 800µg/L,respectively.
<br /> Concentrations detected in NP-1-70' and-90 were lower than the previous November 1999
<br /> event. Concentrations in NP-1-80'and SVE-north were similar to the November 1999
<br /> previous event_Concentrations detected in SVE-South were higher than those of the
<br /> November 1999 sampling event.
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