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Cheaper#76,890 N Main St,Manteca,Califorma <br /> December 22,1995 <br /> Page 17 <br /> Additional Risk Assessment <br /> A residual contamination volume analysis was conducted to estimate the amount <br /> of petroleum hydrocarbons that may be present in the soil at this site. Using <br /> drawings from Kleinfelder reports of soil removal (1987) and comparing them with <br /> locations of Parker soil samples B2, B3 and B4 (May, 1992) shows an area of about 227 <br /> ftZ under the former pump island location. <br /> Xleinfelder's sample #9 from 15 feet BGS had the highest contamination, showing <br /> 31 ppm TPH-g. The distance from that sample and the water level (21.75 & 21.48 ft <br /> BGS) when traces of contamination were detected in groundwater samples is 6.62 <br /> feet. This gives a volume of soil that may be contaminated as 55 72 yards between <br /> the capillary zone and the 1987 excavation bottom. <br /> Less than one gallon of gasoline, about 3 quarts, is present in the 55 72 cubic yards of <br /> soil, as determined by using the following equation. <br /> 31 mg gas 1273Kg sod gallon gas 3 <br /> X 3 X 6 = 0.01409 gallon per yd � <br /> Kg sod yd sod 2.8x10 mg/gallon <br /> 0.01409 gallon l yd3 x 55 72yd3- 0.79 gallon gasolme <br /> Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 <br /> Phone (510) 439-1024 Fax (510) 439-2566 <br />