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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 14 <br /> Affected depth: 15 to 25 ft bgs <br /> Total depth considered for treatment: 30 ft bgs <br /> Total volume: 2,960 cubic yards <br /> • EAST: The lateral and vertical extent of soil contamination to the east has been <br /> defined by SB-23-95. Only minor concentrations of PNAs and petroleum <br /> hydrocarbons were detected between 11 and 16 ft. bgs and none were detected <br /> at 24 ft. bgs <br /> • WEST: Continuous soil samples from the boring for monitoring well MW-12, <br /> located to the west of Sl, were collected for lithologic description only. <br /> Lampblack was observed between 2 and 2.5 feet bgs. OVM readings and visual <br /> observations of the soil from MW-12 indicate the vertical extent of the MGP <br /> residues was limited to between 2 and 2.5 feet bgs. Native material was <br /> encountered at 3 ft. bags. Since MW-12 is located on the property boundary <br /> (which would act as a boundary for former MGP activities), and only 6 inches of <br /> lampblack were observed at 2 feet bgs, MW-12 defines the lateral and vertical <br /> extent of MGP residues to the west. <br /> • SOUTH: To the south, SB-3B and SB-3-95 define the lateral extent of MGP <br /> residues. However, since refusal was encountered in both these borings at <br /> approximately 15 feet bgs, the definition of the vertical extent of MGP residues <br /> could not determined. Data from borings MW-9 and MW-19 indicate native soil <br /> in this area occurs at approximately 25 feet bgs in this area and since MGP <br /> residues are typically limited to the fill material, the vertical extent of the <br /> residues was assumed to be above 25 feet bgs. SB-5-95 further confirms that <br /> MGP residues are limited to the area within the footprint of the former gas <br /> holder. <br /> • NORTH: Since analytical detections and visual observations from three borings <br /> directly adjacent to the footprint of the former gas holder, SB-23-95 to the east, <br /> MW-12 to the west, and SB-5-95 to the south, indicate that the MGP residues do <br /> not extend past the boundaries of the footprint of the gas holder, it was <br /> estimated that the northern extent of MGP residues is also limited to the <br /> footprint of the gas holder. <br /> • VERTICAL: Analytical results of the soil samples from boring MW-9 indicated <br /> the vertical extent of the MGP residues is between 25 and 35 feet bgs. Native <br /> material was encountered at 25 feet bgs in MW-9. PNAs or petroleum <br /> hydrocarbons were not detected in the 50 feet bgs soil sample from MW-19, <br />