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' • 0 <br />i' <br />1 <br />I <br />1 <br />Section 7 <br />CONCLUSIONS <br />The following conclusions are based upon the results of this subsurface investigation at the McMullin Gas <br />Dehydrator Station: <br />1. The subsurface soils consist of interbedded layers of silt and sand. <br />2. Groundwater was encountered in several of the borings at a depth of approximately <br />13 feet. <br />3. Petroleum hydrocarbons were reported in soil samples collected from four of the boreholes <br />at the site (B-1, B-2, B-3 and B-9). The highest levels of petroleum hydrocarbons were <br />reported from the 12'/: -ft sample collected from B-3. This soil sample contained TPH-G <br />(880 mg/kg), TPH-K (640 mg/kg), benzene (1.3 mg/kg), toluene (2.1 mg/kg), ethylbenzene <br />(24 mg/kg) and xylenes (35 mg/kg). <br />4. The petroleum hydrocarbons identified in the soil samples consist primarily of a mixture of <br />gasoline and kerosene -range hydrocarbons. <br />5. Based on the results of the regional well survey, the nearest groundwater well to the site is <br />located about 200 feet to the east (Hofinan Well No. 5). Water samples collected from <br />this well on April 27 indicated diesel -range hydrocarbons at a concentration of 160 ntl; <br />all other analytes (TPH-G, TPH-K, TPH-MO and BTEX) were not detected. On June 18, <br />1993, samples were collected upstream and downstream of the water supply well's <br />pressure tank, and the laboratory reports indicate that the samples did not contain <br />detectable levels of petroleum hydrocarbons (TPH-G, TPH-K, TPH-D, TPH-MO) or <br />volatile organics (BTEX). Based on a review of available literature and discussions with a <br />veterinarian at UC Davis, 160 µg/1 TPH-D is very near the odor and taste threshold for <br />diesel and is not likely to present a risk to the health of the cattle or the environment. <br />cca08/19/93(9660a.doc/cp43) 7-1 <br />