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SUBSURFACE SOIL AND GROUNDWATER ASSESSMENT REPORT l TABLE 1 RESULTS OF SOIL SAMPLES COLLECTED BY GROUND ZERO ANALYSIS, APRIL 7,2000 (micrograms per kilogram ug/l or equivalently, parts per billion) Sample Identification DTU-SP-A1/A2 Constituent DTU-T1N-13' DTU-TIS-13' (composite) DTU-SPB DTU-SPC TPHg <10 <10 <10 <10 <10 Benzene <3 0 <3 0 <3 0 <3 0 <3 0 Toluene <3 0 <3 0 <3 0 <3 0 <3 0 Ethyl-Benzene <3 0 <3 0 <3 0 <3 0 <3 0 Xylene p 25 <3 0 <3 0 4 7 MTBE W11 460/6600 15300111000 1331<5 89/45 12200/2600 DIPE <250 <500 <5 <10 <500 ETBE <250 <500 <5 <10 <500 TAME <250 <500 <5 <10 <500 TBA <1000 <2000 <20 480 <2000 TPHg= Total petroleum hydrocarbons as gasoline MTBE=Methyl tertiary butyl ether analyzed using EPA method 8020/analyzed using EPA method 8260 DIRE=Diisopropyl ether ETBE=Ethyl tertiary butyl ether TAME=Tertiary amyl methyl ether TBA=Tertiary butyl alcohol <1 0=concentration less than indicated laboratory reporting limit UST had the fill pipe installed on the south end and the vent pipe exiting on the north end Soil borings TP-2 and TP-3 were drilled on the east and west sides of the former UST cavity to determine whether impact from MTBE had migrated laterally beyond the limits of the excavation Soil conditions were observed in continuous cores from the surface to maximum depths ranging from 20 to 24 feet bgs Boring logs from this investigation are provided in Attachment A Native subsurface matenals were generally fine-grained materials consisting of clayey sandy-silt Backfill materials encountered in the UST excavation consisted of heterogeneous mixtures or pea gravel, compacted silty clay,and sand The consistency of the UST excavation backfill materials was typically much less dense than the native materials No physical signs(i a odor,discoloration)of petroleum impacted soil were identified in any of the soil bonngs dunng drilling operations Following the completion of each soil boring, a Hydro-punch in-situ groundwater-sampling tool was driven into the groundwater-bearing zone from depths ranging from 20 to 24 feet Groundwater extracted from each soil boring appeared relatively free of sediment and ESA field = geologists did not detect petroleum odors or hydrocarbon sheen on the water samples Laboratory analytical results of soil and groundwater samples are summarized on Table 2 In the soil sample collected from bonng TP-4 at 15 feet bgs, I I milligrams per kilogram(mg/kg) of . MTBE was detected Groundwater samples collected from borings TP-4W and TP-5W contained 1,300 micrograms per liter(gg/L)and 14µg/L,respectively of MTBE Additional Grounduaier Assessment Report 4 ESA/200252 March 26 2001