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M f p <br /> CLEARWATER <br /> GROUP INC <br /> En e r ro rr rn,n l n! Strr ins <br /> 4.0 RESULTS <br /> 4.1 Water Level Gauging Data <br /> I � <br /> On August 20, 1996, the depths to groundwater in the six monitoring wells ranged <br /> from 19 64 to 20 66 feet below the top of casing Groundwater elevations, calculated <br /> for the purpose of estimating flow direction and gradient, were approximately 0 8 <br /> foot lower than groundwater elevations measured on May 30, 1996 The <br /> groundwater elevation contours shown on Figure 3 indicate that groundwater flow <br /> is toward the northwest The groundwater gradient is 0 015 foot/foot (15%) across <br /> most of the site, but is only 0 004 foot/foot (0 4%) between MW-2 and MW-6 This <br /> change it gradient appears as a flattening of the water table west of the former USTs, <br /> which is consistent with the configuration of the water table during previous <br /> gauging events <br /> 4.2 Groundwater Analytical Results <br /> TPHg and BTEX were not detected in the groundwater samples from monitoring <br /> wells MW-3 and MW-4, the samples from MW-1 and MW-6 contained benzene <br /> concentrations of 10 parts per billion (ppb) and 0 5 ppb, respectively The maximum <br /> concentrations of TPHg and BTEX were in the sample from MW-2, it contained <br /> 30,000 ppb TPHg and 180 ppb benzene, respectively. <br /> � <br /> MTBE was not detected in the sample from MW-2, although the detection limit was g <br /> 300 ppb because of the high concentrations of target compounds MTBE was detected <br /> in the samples from MW-1, MW-3, MW-5 and MW-6 in concentrations of 14 ppb or <br /> less <br /> Benzene and MTBE were not detected in MW-6 samples during previous sampling <br /> events However, the concentrations detected during the third quarter sampling <br /> event are at the laboratory reporting limit for benzene (0 5 ppb) and only slightly <br /> above the reporting limit of 5 ppb for MTBE We believe that the dissolved <br /> j hydrocarbon plume remains delineated by monitoring wells MW-1, MW-3, MW-4 <br /> and MW-6 <br /> j A summary of groundwater elevations and analytical results is presented on Table <br /> 1 Hydrocarbon concentrations are presented graphically on Figure 4 Copies of the <br /> laboratory report and chain-of-custody form are attached as Appendix B <br /> D-101 2Q96 3 September 20, 1996 <br />