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' 01 June 1999 AGE-NC Project No 95-0137 Page 3 of 26 25 UST REMOVAL Four underground storage tanks (USTs) were removed from the site on 15 July 1987 One 10,000- gallon diesel tank(Tank#1)and one 7,500-gallon diesel tank(Tank#2)were located near the tuning shop One 10,000-gallon unleaded gasoline tank(Tank#3)and one 10,000-gallon diesel tank (Tank #4)were located approximately 120 feet east of the shop After removal, one sample was collected below each UST at depths between 18 and 21 feet below surface grade (bsg) Petroleum hydrocarbons were detected in soil samples collected below Tanks#1, #2, and#3 Analytical results of the UST-removal soil samples are summarized in Table 1 ' 3.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER In April 1994, eight soil borings (B1 through 138) were drilled at the site Figure 2 depicts the ' locations of the soil borings Three of the borings were completed as ground water monitoring wells (MW-1, MW-2 and MW-3) During drilling, ground water was encountered at a depth of approximately 20 feet below surface grade (bsg) • Total petroleum hydrocarbons quantified as gasoline (TPH-g) were detected in ten soil samples at concentrations as high as 3,800 milligrams per kilogram(mg/kg) Total petroleum ' hydrocarbons quantified as diesel(TPH-d)were detected in twelve samples at concentrations as high as 9,000 mg/kg The maximum concentration of TPH-g was detected in sample B4- 20, the maximum TPH-d was detected in sample 138-20 ' TPH-g was detected in ground water samples from MW-1, MW-2 and MW-3 at concentrations of 1,700 micrograms per liter(gg/1), 14,000,ug/l and 2,600 pg/l, respectively TPH-d was detected in the MW-1, MW-2 and MW-3 samples at concentrations of 2,400 µg/1, 9,200 ,cg/l and 6,900,ug/l, respectively With the exception of one sample(134-20), concentrations of TPH-d exceed concentrations of TPH-g In the soil samples Analytical results of soil samples are included in Table 2 Analytical results of ' ground water samples are included in Table 3 In August 1995, five additional soil borings (139 through B 13)were drilled at the site Two borings ' were completed as ground water monitoring wells west and south of the previous three wells (MW-4 and MW-5) During drilling, ground water was encountered at a depth of approximately 20 feet bsg ' TPH-g was detected in four soil samples at concentrations as high as 23 mg/kg TPH-d was detected In six soil samples at concentrations as high as 1,900 mg/kg Volatile aromatic hydrocarbons (benzene, toluene, ethyl benzene BTEX) were not detected In any of the soil samples analyzed Advanced GeoEn%tronmental,Inc 1