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ArAWues Working to Restore Nature (4) Based on our interpretation, soil containing ethylbenzene remains in place between 15 to 40 feet bsg (boring BH-1 and southeast corner of the tank cavity) with an area affected shown on Plate 10 of approximately 250 square feet Therefore the total volume affected is approximately 6,250 cubic feet Using 0 2 mg/kg as the average ethylbenzene concentration in the soil, the total pounds of ethylbenzene (E) were calculated as follows E = 0 2 mg/kg X 1x10 kg/mg X 6,250 ft3 X 123 1b/ft3 = 153 lb of ethylbenzene (5) Based on our interpretation, soil containing total xylenes remains in place between 15 to 40 feet bsg (boring BH-1 and southeast cor*ier of the tank cavity) with an area affected shown on Plate 10 of approximately 250 square feet Therefore the total volume affected is approximately 6,250 cubic feet. Using 3 25 mg/kg as the average total xylene concentration in the soil, the total pounds of xylenes (X) were calculated as follows X = 3 25 mg/kg X 1x10 kg/mg X 6,250 ft3 X 123 1b/ft3 = 2 49 lb of total xylenes Dissolved Hydrocarbons in Groundwater Results ofg roundwater morutoring show that concentrations of TPHg and BTEX were below detection limits in wells MW-1 through MW-4 during the last four quarters, however, well MW-1 was dry during two sampling events Cumulative results of groundwater samples are presented in Table 3 Source Removal Because the two 1000-gallon gasoline tanks were removed and approximately 500 cubic yards of impacted soil was removed during soil excavation, it appears there are no ongoing onsite sources of petroleum hydrocarbons that could affect soil or groundwater at this site Approximately 623 pounds of TPHg were removed during soil excavation Assuming the average concentration for TPHg at 10,000 ppm. TPHg = 375 mg/kg X 1x10' kg/mg X 13,500 ft3 X 123 1b/ft3 = 622 69 lb of gasoline . 0504gtak/123009 01 5