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WELLS FARGO BANK PROPERTY <br /> 49 SOUTH WILSON WAY <br /> STOCKTON, CALIFORNIA <br /> DECEMBER 28, 1998 <br /> Page 7 <br /> 34.5 lbs. = 5.3 gallons of TPH-g <br /> 6.48 lbs/gallon <br /> Based on the above calculations there is approximately 1 60.2 pounds or 86.4 gallons of <br /> TPH-g remaining in the soil beneath the subject site. <br /> L " <br /> TPH-g Concentrations in Groundwater <br /> •• Groundwater samples collected Wells MW-2 and MW-4; as well as Boring B-5 during the <br /> last quarterly groundwater monitoring event were reported to contain TPH-g in <br /> concentration ranging from 3.8 to 13 ppm. Benzene was detected in Well MW-2 and <br /> Boring B-5 in concentrations of 8 and 2 ppb. Wells 1VIW-1 and MW-3 were reported to <br /> not contain detectable concentrations of TPH-g or BTEX. No fuel oxygenates were <br /> detected in any of the groundwater samples collected during the last quarterly sampling <br /> event. A summary of the results of groundwater samplia!g at the subject site is provided in <br /> Table 1. <br /> Mass Balance Analysis for TPH-g in Groundwater <br /> A Mass Balance Analysis was conducted to determine the approximate amount of TPH-g <br /> dissolved within the groundwater beneath the subjectl� site. In order to calculate the <br /> approximate amount of TPH-g the thickness of the impacted aquifer was estimated to be <br /> approximately 30 feet thick. This thickness was based upon concentrations TPH-g <br /> detected within soil samples collected in this area. Additionally, the total porosity was <br /> assumed to be equal to the effective porosity. TPH-g concentrations within the <br /> groundwater were based upon the average of TPH-g conA entrations reported in Wells MW- <br /> 2 and MW-4, and Boring B-5. The estimated total amount of TPH-g dissolved in the <br /> groundwater beneath the site is as follows: <br /> Porosity = 38.76% <br /> Estimated area and thickness of impacted aquifer= 1,052 square feet, 30 feet thick <br /> Estimated volume of the impacted aquifer= 31,560 cubic feet <br /> Average TPH-g concentration in groundwater= 8.4 ppm <br /> } <br /> 31,560 cubic feet x 38.67% = 12,204 cubic feet of pore space <br /> 12,204 cu. ft. x 7.48 gallons/cu. ft. x 8.4 = 0.76 gallons of TPH-g <br /> 1,000,000 i <br /> 3 <br /> i <br /> or <br /> i <br /> 0.76 gallons x 6.48 lbs./gallon = 4.9 lbs. of TPH-g <br /> !i <br />