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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 13 <br /> field work and the presence of former MGP structures and fill were use to help <br /> define the potential soil source areas. <br /> Boring logs from five of the borings (MW-9, SB-3B, SB-2-95, SB-3-95, and SB-4-95) <br /> indicate that concrete or wood barriers were encountered at depths ranging from 15 <br /> to 23 feet below ground surface (bgs), suggesting the presence of the former gas <br /> holder foundation at this depth. Perched water was noted in borings MW-9 and SB- <br /> 2-95 immediately above the encountered barrier at 12 feet bgs. The presence of <br /> perched water is important because organic fluid may also be present and contained <br /> by the barrier. Chemical data for Sl are summarized in attached Table 4-1. <br /> Analytical results indicate that elevated concentrations of PNAs and TPH as diesel <br /> are generally limited to the soil between 20 and 25 feet bgs. Total PNA <br /> concentrations in soil samples collected in Sl above 20 feet bgs ranged from none <br /> detected to 13 mg/kg. Total PNA concentrations in samples collected below 25 feet <br /> bgs ranged from none detected to 1.28 mg/kg. <br /> TPH-gasoline and related BTEX were detected in some of the soil samples in S1. <br /> The highest concentrations of TPH-diesel were detected at 20 feet bgs in SB-4-95 <br /> (260 mg/kg) and at 24 feet bgs in MW-9 (5,425 mg/kg). In deeper samples from <br /> MW-9 and MW-19, TPH-diesel was either not detected or estimated to be at or <br /> below the detection limit. <br /> Cyanide was detected in one sample collected within this area. It was reported in <br /> MW-9 at 139.5 mg/kg at 24.5 feet bgs. Cyanide was not detected in other samples <br /> from Sl. Cyanide does not appear to be widely distributed in the soil at this site but <br /> may be found intermittently. <br /> In summary, Sl comprises fill material containing PNAs and TPH-diesel within the <br /> footprint of a former gas holder. The below grade portion of the gas holder appears <br /> to still be present. Visual and analytical results from soil borings located in and <br /> around the footprint of the former gas holder indicate the extent of PNA and TPH- <br /> diesel is limited to the fill material within the footprint of the former gas holder and <br /> at a depth between 15 and 25 feet bgs. The highest concentrations of PNAs and <br /> TPH-diesel were detected at 24 feet bgs in MW-9. <br /> The lateral and vertical extent of S1 is further summarized below: <br /> Area covered: 592 sq. yards, lateral extent defined by outer edge of former gas <br /> holder <br />