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• Report of Findings Frontier Transportation 0702-177 September 5,2002 Page 3 backfilled with a grout mixture of 5% bentonite powder, Portland cement, and water grout using a tremie pipe to seal the hole from the bottom up. All soil cuttings and casing material were containerized in 55-gallon drums. A well abandonment permit was obtained from the PHS/EHD on May 15, 2002. Mr. Sam Savig of the PHS/EHD was on-site to witness the well abandonment. 1 From May 20 through 24, BEII excavated a total of 325 tons of soil near the former UST area. The excavation pit measured 30 feet by 30 feet by 15 feet deep. The soil consisted of heterogeneous clays with some fine-grained silty sand stringers at groundwater depth. 1 Groundwater was encountered in the silty sand at approximately 13' bg. The excavation pit was terminated at 15' bg to avoid collapsing of the pit from the entry of silty sand and groundwater. A total of sixteen soil samples were collected from the excavation pit sidewalls at depths of 4' bg ' and above (12' bg) or below (14' bg) groundwater. See Figure 4 for pit soil sample locations. Soil samples were analyzed for TPH-d, TPH-g, BTEX, and MTBE with EPA methods 8015 modified and 8260B by an on-site mobile laboratory (See Table 2 for Pit Soil Sample Results ' and Appendix B for Laboratory Analytical Reports). Mr. Sam Savig of the PHS/EHD was on- site to witness the pit excavation. ' Soil sample results identified low level petroleum concentrations at 4' bg. The maximum TPH-d concentration in soil was 36 mg/kg along the south side of the western sidewall. No other detectable concentrations of TPH-d were identified from the remaining seven samples ' collected at 4' bg. Soil sample Top SES collected from the southeast sidewall identified a maximum TPH-g concentration of 11 mg/kg. The remaining seven soil samples contained TPH- ' g concentrations at<_4 mg/kg. Soil sample Top NWS collected from the northwest sidewall contained the highest BTEX(153 µg/kg) and MTBE (130 µg/kg) concentrations at 4' bg. Only two other soil samples, Top WSS and Top SWS, identified detectable BTEX concentrations at 25 pg/kg and 8.5 µg/kg (exclusively as ethylbenzene and xylene). MTBE concentrations ranged from 92 gg/kg to 7.5 pg/kg in the remaining seven soil samples collected at 4' bg (See Table 2). ' Soil sample results identified higher petroleum hydrocarbon concentrations just above encountered groundwater(13' bg). Five soil samples were collected from the capillary fringe at 12' bg. The maximum TPH-d concentration was contained in soil sample Bot NES collected ' from the northeast sidewall as 700 mg/kg. The remaining four soil samples collected at 12' bg contained TPH-d from 600 mg/kg to 32 mg/kg. Soil sample Bot SES collected from the southeast sidewall identified maximum TPH-g concentrations of 640 mg/kg at 12' bg. TPH-g concentrations ranged-from 350 mg/kg to 3.2 mg/kg in the rest-of the soil samples collected-at — --- 12' bg. Maximum BTEX concentrations in soil were identified as 59,100 µg/kg from the northwest sidewall (Bot NWS at 12' bg) most of which was xylene. The other samples collected ' at 12' bg contained BTEX from 47,330 µg/kg to <83.1 pg/kg. MTBE concentrations were