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1 <br /> APPENDIX B <br /> CALCULATION OF MASS REMOVED AND REMAINING AT EACH FORMER TANK <br /> SITE <br /> This appendix describes ERM's procedures and rationale for estimating the mass of <br />' cherrucals removed and remaining at former tank sites 1 and 2 <br /> Mass Removed <br /> ERM used the results of soil and ground water samples collected at each tank excavation <br />' along with known volumes of soil and ground water removed to estimate the mass of <br /> chemicals removed at each former tank site <br />' At former tank site 1, the average concentration of TPH-g detected in soil samples <br /> collected from the sidewalls of the excavation was 2,100 mg/kg and 200 tons of soil was <br /> removed from the excavation Assuming the average TPH-g concentration for all soil <br /> removed was 2,100 mg/kg, the resulting estimate of chemicals removed is 840 pounds <br /> Similarly, the TPH-g concentration in a ground water sample collected from the tank <br /> excavation was 45 mg/1 During the first tank excavation stage,4,000 gallons of ground <br /> water was removed from the excavation Assuming the average TPH-g concentration of <br /> all extracted ground water was 45 mg/l, the resulting estimate of chemicals removed is <br />' 15 pounds During subsequent dewatering stages, the average TPH-g concentration <br /> detected in ground water was 75 mg/1 and 8,280 gallons of water was removed <br /> Assuming this average for all ground water, chemicals removed from the former tank site <br />' during this dewatering are estimated to be 5 2 pounds <br />' At former tank site 2, the average concentration of TPH-g detected in soil samples <br /> collected from the sidewalls of the excavation was 1,000 mg/kg and 152 tons of soil was <br /> removed from the excavation Assuming that 1,000 mg/kg was the average soil <br /> concentration for all soil removed, the resulting estimate of chemicals removed is 304 <br /> pounds Similarly, the TPH-g concentration in a ground water sample collected from the <br /> tank excavation was 84 mg/l During the first tank excavation stage,4,000 gallons of <br />' ground water was removed from the excavation Assuming 84 mg/1 was the average <br /> TPH-g concentration for all extracted ground water, the resulting estimate of chemicals <br />' removed is 2 8 pounds During a subsequent dewatering stage, the average TPH-g <br /> concentration in ground water was 47 mg/1 and 4,120 gallons of water were removed <br /> This results in another 16 pounds of chemicals removed from the former tank site <br /> 1 <br /> ' B-1 <br />