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SECTIONTHRE E 118MA.IV818 <br /> 1993 were screened deeper to account for the lowering depth to groundwater However, the <br /> groundwater table started to rise in 1994 and the groundwater level was above the screen interval in <br /> many of the wells following 1996 Table 3-6 summarizes groundwater data for samples that were <br /> collected when the water table was within the screen interval Three of the wells have large screen <br /> intervals from 45 feet to 85 feet of screen,VW-1, VM-1 and VM-2, which may affect the groundwater <br /> concentrations in the wells Therefore the groundwater data were also summarized without these three <br /> wells with the larger screen intervals on Table 3-7 The following table summarizes the groundwater <br /> data analysis <br /> SUAEWARV OF 95%UCL GROUNDWATER CONCENTRATIONS <br /> CONCENTRATIONS in pe <br /> Summary of Summary of Summary of Summary of Summary of <br /> All Older Recent Groundwater Groundwater <br /> Groundwater Groundwater Groundwater Data Collected Data Collected <br /> Data Data 1987- Data 1993- Within Well Witton Well <br /> (Table 3-3) 1992 1998 Screen Screen(4.5') <br /> (Table 3-4) (Table 3-5) (Table 3-6) (cable 3-7) <br /> Benzene 2,330 8,537 1,689 6,118 5,571 <br /> Toluene 1,982 13,205 580 5,631 7,879 <br /> Ethylbenzene 276 1,120 1821 7,511 712 <br /> Xylenes 9786 51084 498 2,653 3,105 <br /> MTBE 8 7 Not analyzed 921 37 5 1 <br /> For purposes of the risk assessment and groundwater impact analysis, all of the above scenarios were <br /> used and is discussed in greater detail in Section 4 0 <br /> EPA Method 8260 was ran for all VOCs for a select number of samples in 1998 In a few of the <br /> groundwater samples, 1,2-dichloroethane was detected in concentrations ranging from below the <br /> reporting limits to 0 46 mg/l In order to be conservative and protective of human health and <br /> groundwater, 1,2-dschloroethane was assumed to be in all wells at a concentration of 0 46 mg/1 <br /> Additionally the following VOCs were detected infrequently in the wells (2 or less samples) tert- <br /> butylbenzene, naphthalene, isopropylbenzene, 1,2,4-tnmethylbenzene, styrene, tetrachloroethene, and <br /> T110871B73ODDNAMOGKTOMRaMRTSHOREPm D0G18-FER4M730WNA%Sm 34 <br />