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Based on ground water levels measured on April 7, 1992, the average depth <br /> . to ground water beneath the site is 66 feet below grade (fbg) and ground <br /> water gradient onsite is estimated to be 0.002 foot per foot to the east <br /> ® Concentrations of 270 and 4 parts per mullion (ppm) of total petroleum <br /> hydrocarbons as gasoline (TPH-G) and 4 4 ppm and 0.81 ppm of benzene <br /> were detected in soil samples collected beneath the former tank cavity at <br /> depths of 46 and 56 fbg <br /> © The former underground fuel tanks and/or associated product lines are the <br /> likely source of the adsorbed-phase hydrocarbons. <br /> ® Ground water has been impacted with dissolved-phase hydrocarbons. This <br /> may have been caused by the adsorbed-phase hydrocarbons detected in the <br /> soil. <br /> Test Wells Construction <br /> The screened interval and total depths of the monitoring wells used in the soil vapor testing <br /> activities are shown in the Table 1 below Well Locations are shown in Figure 2 <br /> TABLE 1 <br /> MONITORING WELL CONSTRUCTION DETAIL <br /> Monitoring Total Screened Casing Diameter Casing Material <br /> Well IIID Well Depth IInterval (inches) <br /> in fbg (in fbg) <br /> MW-1 50 30 - 50 4 PVC <br /> MW-2 45 30 - 45 4 PVC <br /> MW-3 485 285 - 48 5 4 PVC <br /> MW-4 50 30 - 50 4 PVC <br /> MW-10 75 35 - 75 4 L PVC <br /> SOIL, VAPOR TESTING ACTIVITIES <br /> On May 28, 1992, a vapor extraction test was performed by extracting soil vapor from the <br /> screened section within the hydrocarbon-affected soil in the vadose zone in MW-10, and <br /> monitoring vacuum response in surrounding wells (MW-1, 2, 3, and 4, see Figure 2). The <br /> 2 <br />