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LEED5NILL•HERNENHOFF,WC. <br /> f <br /> Sample Analysis <br /> Initially, only select soil samples will be analyzed. All other samples <br /> will be properly preserved in the laboratory. It is anticipated that soil <br /> samples collected from a depth of 2, 5, 15, and 25 feet will be initially <br /> analyzed. Depending on the analytical results of this initial round of <br /> sample analysis, additional deeper soil samples may be tested. The samples <br /> will be analyzed for constituents normally found in gQsoline; benzene, <br /> toluene, xylene, and ethylbenzene (BTX&E), and total petroleum hydrocarbons <br /> as gasoline (TPH). <br /> GROUNDWATER INVESTIGATION <br /> Monitoring- Well Installation <br /> The direction of groundwater flow was never established in the Balbi & <br /> Chang report. Therefore, a licensed surveyor was retained to establish <br /> reference point elevations (RP) on the casings of the three existing <br /> monitoring wells. from this RP elevation, LH carefuiiy measured the depth <br /> to water in each well, calculated the water surface elevation and was able <br /> to establish the direction of groundwater flow to be northeasterly across f . <br /> the site. See Table 2. <br /> In July of 1989, representative groundwater samples were.collected by LH <br /> from each of the three monitoring wells. The results correspond with <br /> Balbi & Chang's reputed results; MW-1 and MW-3 showed trace amounts of <br /> BTX&E but no detectable concentrations of TPH (as gasoline) and MW-2 showed <br /> high concentrations of both BTX&E and TPH (as gasoline). Due to these <br /> findings, LH proposes the installation of two additional monitoring wells <br /> to determine whether the contamination is linked to an on- or off-site <br /> source(s). Monitoring Well 4 is to be located upgradient of the former <br /> tank excavation near the southwest corner of the site, and Monitoring Well <br /> 5 will be located downgradient of the former tank excavation in the <br /> northeast corner (see Figure l). These wells will help determine whether <br /> upgradient, offsite groundwater contamination is entering the site. <br /> Location of the monitoring wells is shown on Figure 1. <br /> 7 <br />