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Analytical Results
<br /> Data from the March 2001 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), and 1,2-Dibromoethane,also known as ethylene dibromide (EDB). Analytical
<br /> results are presented in Tables 4,5,and 6. Table 4 presents groundwater sample analysis for
<br /> TPH-gasoline and benzene,toluene,ethyl benzene,and xylenes (BTEX). Table 5 presents
<br /> analytical results for MTBE and other oxygenate compounds. Table 6 presents analytical
<br /> results for 1,2-DCA and EDB.The results are summarized below,dependent upon the
<br /> location of the well in relation to the plume: upgradient,cross-gradient,or within the
<br /> plume.
<br /> Upgradient Wells-MW-DIS-5,-6,-7S, -71),-8S,and-81),
<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 /> r .
<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.There were no detections of these compounds in these wells.
<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 /> 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). TPH as gasoline concentrations in MW-DIS-1 increased from
<br /> the previous successful sampling event on 3/29/2000. Concentrations continue to decline
<br /> in MW-DIS-2.
<br /> Oxygenates
<br /> Methyl-tert-Butyl Ether(MTBE), tert-Butanol(TBA), Di-isopropyl ether(DIPE),Ethyl-tert-
<br /> butyl ether(ETBE),and tert-Amyl Methyl ether(TAME)were not detected in any of the
<br /> wells during this monitoring event. All oxygenates were analyzed by EPA Method 8260B
<br /> during this sampling event.
<br /> There have been no confirmed detections of the MTBE,DIPE,ETBE,and TAME at this site.
<br /> TBA has been detected once,in five different wells,and twice in MW-DIS-1 and SVE-North.
<br /> TBA has been non-detect for four quarters in all wells except SVE-North. TBA will continue
<br /> I`
<br /> to be analyzed in SVE-North on a semi-annual basis.
<br /> Other Additives
<br /> All monitoring wells were sampled and analyzed for oxygenates, 1,2-DCA and EDB during
<br /> this sampling event. These compounds are known as lead scavengers and were a common
<br /> gasoline additive.
<br /> r EDB was detected in NP-1-80'and SVE-South at concentrations of 1000 and 510 ug/L,
<br /> respectively. EDB was detected in MW-DIS-1,NP-1-90',NP-1-70',and SVE-NORTH during
<br /> ` the previous sampling event. 1,2-DCA was detected in MW-DIS-1,NP-1-80',NP-1-70', and
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