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the presence of a water main Visual observations indicated that the soils were clean, however, no confirmation sample was collected along the south wall Residual benzene and TPH-g may be present in this area, however, due to the lack of confirmation sample, the exact concentration is unknown No other soil borings collected above the ground water table in the vicinity of former tank site 1 contained detectable concentrations of ' TPH-g and BTEX Figure B-5 presents the results of soil samples collected in the immediate vicinity of the former tank 1 location For mass estimating purposes, ERM conservatively assumed that the concentration of TPH-g detected along the north, west, and east sxdewalls represents the average concentration along the wall of the excavation For the south wall, ERM very conservatively assumed that the average concentration of chemicals in soils removed from the tank excavation is consistent with soils remaining along this sidewall. The concentrations were then multiplied by the length of the sidewall excavation, the depth to ground water (i e , 5 feet) and an assumed width of 3 feet (based on the non.-detect TPH-g concentration 1n step-out samples at HB-15 and HB-19) Table B-3 presents the ' calculations performed As shown, 64 pounds of chemicals are calculated to remain in soil at former tank site 1 Almost all (i e, 63 pounds) of this material is associated with soils that could not be excavated along the south wall At former tank site 2, confirmation samples were collected along the north, south, east, and west sidewalls of the final tank excavation (UST 2--1, UST 2-3, UST 2-6, and UST 2-7) Along the north wall, the TPH-g concentration detected in the sidewall sample was 20 mg/kg Along the south wall, TPH-g was detected at a concentration of 550 mg/kg, ' however, a soil sample collected 3 feet further south (HB-13) had a TPH-g concentration of only 5 2 mg/kg, indicating that the TPH-g concentration decreases rapidly from the final excavation wall Similarly, the remaining TPH-g concentration detected in soil from the ieastern sidewall was 1,500 mg/kg, however a soil sample collected 3 feet further east (HB-14) had a TPH-g concentration of <5 mg/kg Finally, along the western wall, TPH-g was detected at a concentration of 14,000 mg/kg, however a soil sample collected 3 feet further to the west (HB-11) had a TPH-g concentration of <5 mg/kg Excavation was performed as far as possible to remove impacted soils along the western sidewall, however, the presence of a water main and the building precluded additional excavation in this direction All other soil borings collected above the ground water table in the vicinity of former tank site 2 did not contain residual concentrations of TPH-g and BTEX ' Figure B-6 presents the results of soil samples collected 1n the immediate vicinity of the former tank 2 location ' ERM performed mass calculations by conservatively assuming the TPH-g concentration detected in the sidewall samples was the average concentration remaining along each sidewall of the final tank excavation The sidewall concentrations were multiplied by the depth to ground water (i e , 5 feet), the length of the sidewall, and the distance to the next clean sample Table B-3 presents the calculations performed As shown, 121 pounds of B-3