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Analytical Results
<br /> Total petroleum hydrocarbons(TPH) as gasoline,and BTEX compounds (benzene,toluene,
<br /> ethyl benzene and total xylenes)were not analyzed during this round of sampling, as they
<br /> are sampled semi-annually,and were sampled during the first quarter of 2000. Table 4
<br /> j presents the:TPH as gasoline and BTEX results from previous sampling events. The
<br /> compounds analyzed during this event include 1,2-Dichloroethane (1,2-DCA), 1,2-
<br /> Dibromoethane,also known as ethylene dibromide (EDB),and oxygenates (Methyl-tert-
<br /> I Butyl Ether(MTBE), tert-Butanol(TBA),Di-isopropyl ether(Dl1'E);Ethyl-tert-butyl ether
<br /> (ETBE), and tert-Amyl Methyl ether (TAME)).
<br /> Data from the June 27 and 28,2000 sampling event indicate that the groundwater beneath
<br /> the Disco site contains detectable levels of 1,2-DCA, EDB,TBA. Analytical results are
<br /> presented in Tables 5 and 6. Table 5 presents analytical results for MTBE and other
<br /> oxygenate compounds. Table 6 presents analytical results for 1,2-DCA and EDB. The results
<br /> are summarized below,dependent upon the location of the well in relation to the plume:
<br /> upgradient,cross-gradient,or within the plume.
<br /> t
<br /> Upgradient Wells-MW-DIS-5, -6,-7S,-71D,-8S,and-81D.
<br /> All u radient wells were sampled and analyzed for oxygenates, and EDB during
<br /> Pg P Y Yg g
<br /> this sampling event.There were no detections of these compounds in these wells.
<br /> i
<br /> Cross-gradient Wells-MW-DIS-3,-9,and—10.
<br /> i 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 /> Oxygenates
<br /> MTBE,TBA,DIPE,ETBE,and TAME were not detected in any of the wells during this
<br /> monitoring event,except SVE-North,where TBA was detected at 56µg/L. TBA was not
<br /> detected in this well in the previous seven sampling events. All oxygenates were analyzed
<br /> by EPA Method 8260 during this sampling event.
<br /> There have been no confirmed detections of the MTBE,D1PE,ETBE,and TAME at this site.
<br /> TBA has been detected once,in three different wells,and twice in MW-DIS-1 and SVE-
<br /> North.
<br /> Other Additives
<br /> All wells were sampled and analyzed for 1,2-DCA and EDB during this sampling event.
<br /> These compounds are known as lead scavengers and were a common gasoline additive.
<br /> EDB was detected in MW-DIS-1,NP-1-90',NP-1-80',NP-1-70',and SVE-South during this
<br /> sampling event at concentrations of 19, 110, 1,300, 150, and 320µg/L,respectively. 1,2-DCA
<br /> was detected in the same wells during this sampling event at concentrations of 63, 180,
<br /> ti 2,300,210,and 760 gg/L,respectively. Concentrations of EDB and 1,2-DCA are consistent
<br /> with the previous sampling event.
<br /> I ,
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