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Section 7 <br /> CONCLUSIONS <br /> The following conclusions are based upon the results of this subsurface investigation at the Lathrop Gas <br /> Dehydrator Station: <br /> 1. The subsurface soils consist of interbedded layers of silt and sand. <br /> 2. Groundwater was measured in the temporary wells at a depth of about 9 feet below the ground <br /> surface. Based on the water level measurements, the water table below the site was relatively flat <br /> with a minimal hydraulic gradient(less than 0.001 ft per ft)to the south. <br /> 3. Based on the results of the regional well survey, the nearest groundwater well to the site is located <br /> about '/z-mile to the north. <br /> 4. Petroleum hydrocarbons were reported in soil samples collected from several of the boreholes at <br /> the site (MW-1, B-2, B-3, B-7 and B-8)primarily from the capillary fringe at a depth of 7'/z to 9 <br /> feet. The highest levels of petroleum hydrocarbons were reported from the 9-ft sample collected <br /> from MW-1 (located near the reboiler discharge line). This soil sample contained TPH-K(4,300 <br /> mg/kg), TPH-G(800 mg/kg), benzene(0.23 mg/kg), toluene (0.21 mg/kg), ethylbenzene (1.3 <br /> mg/kg)and xylenes (34 mg/kg). <br /> 5. Petroleum hydrocarbons were detected in all of the groundwater samples collected except borings <br /> B-6 and B-8. The highest levels of petroleum hydrocarbons were reported from the groundwater <br /> samples collected from MW-1 and B-2 through B4 (located closest to the reboiler unit). The <br /> petroleum hydrocarbons noted in these samples consist primarily of kerosene-range hydrocarbons <br /> and were reported at concentrations up to 47,000 µg/L (MW-1). <br /> cca/08/23/93/9449arpt.doc/mkn4 7-1 <br />