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UST Closure Report Sharpe Defense Distribution Region West Lathrop,California Page 17 Sample;,,, TPH-G TPH-D Benzene Ethyl- Toluene Total MTBE Ethanol Tertiary- DIPE ETBE TAME Lead I.D. (mg/kg) (mg/kg) (µg/kg) benzene (µg/kg) Xylenes (µg/kg) (µg/kg) Butanol (µg/ (µgl (µg/ (mg/ (lLg/kg) (µg/k9) (lAg/kg) k9) kg) kg) kg) PL-10 < 68 < < < < < < < < < < 23 PL-11 < 12 < < < < 16 < < < < < 19 STOCKPILE FROM PIPING TRENCHES SPC- < 28 < < < < 55 < < < < < 19 4+SPC-2 SPC-3 NA NA NA NA NA NA < < < < < < NA GROUNDWATER SAMPLE UST EXCAVATION GW-1-P 0.2 0.05 7.1 <0.3 1.2 49 450 <1.0 <10 <1.0 <1.0 <1.0 NA mg/L mg/L µg/L µg/L µg/L µg/L µg/L µg/L µg/L 99' µg/L µg/L Detection 1 1.0 1.0 5 5 5 5 10 10 100 10 10 10 5.0 limit(soil) Abbreviations: TPH-G=Total Petroleum Hydrocarbons as Gasoline. TPH-D=Total Petroleum Hydrocarbons as Diesel. MTBE=Methyl-t-Butyl Ether DIPE =Di-isopropyl Ether ETBE =Ethyl-t-Butyl Ether TAME=t-Amyl Methyl Ether mg/kg=milligrams per kilogram. µg/kg= micrograms per kilogram. <=less than the method detection limit. NA=not analyzed. 5.1 UST Excavation Floor Soil Samples Concentrations of one to seven of the 12 petroleum hydrocarbon parameters analyzed, ranged from trace to high levels in 11 of the 19 samples collected and analyzed from the floor of the UST excavation. The 11 samples were collected from the west margin, center and southeast margin of the UST concrete pad at a depth of generally 13 feet. Figure 6 shows the concentrations of these parameters at the soil sample site. The concentrations of the parameters in the other 8 samples were less than method detection levels. These samples were collected from the north and northeast margins of the UST pad. Concentrations of MTBE were detected in levels greater than the method detection level (10 µg/kg) in 10 soil samples. MTBE ranged from 8 to 1000 µg/kg. The highest concentration was in the sample (2E) collected from the eastern end of UST #22. The other three highest concentrations of MTBE were in samples from the center of UST#26 (570 µg/kg), at the western end of UST#21 (210 µg/kg) and below the center of UST#24 (180 µg/kg). The sample with 570 µg/kg MTBE (sample `North' from the center of UST #26 pad) also contained relatively high concentrations of benzene (100µg/kg), toluene (50 µg/kg) and total xylenes (110 l.tg/kg). The sample with the highest concentration of MTBE (1000 µg/kg in 2E), N:\PROJECTS\3546\Reports\3546 UST Closure Report Draft.doc March 24,1999