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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 15 <br /> indicating the MGP residues do not extend to 50 feet bgs at this location. Strong <br /> odors in the soil from MW-19 were limited to the soil above 25 feet bgs. <br /> Comment: <br /> 10. Pages 4-6 and 4-10, Section 4.2 1.2, Potential Source Area 2 (S2) <br /> The inconsistent sampling program observed in Sl also is evident in S2. SB-2 was sampled <br /> to a maximum depth of only eight feet bgs. Consequently, in spite of detecting 6,234 mg/kg <br /> total PNAs and 64 mg/kg total VOCs at eight feet bgs, no additional data are available. <br /> Furthermore, TPHd and TPHg were not analyzed in the sample. The sampling protocol used <br /> in MW-9 also was used in B-17, resulting in lack of information beyond 16.4 feet bgs where <br /> total PNAs and TPHd were detected at 1,700 mg/kg and 1,574 mg/kg, respectively. SB-7-95, <br /> which was sampled at a maximum depth of 22 feet bgs, had 2,165 mg/kg total PNAs, 27 <br /> mg/kg total VOCs, 380 mg/kg TPHg, and 9,900 mg/kg TPHd. Thus, the lateral and vertical <br /> extent of contamination to the north has not been defined. <br /> B-17 which is the westernmost sample location, also does not define the contamination to the <br /> west. Definition also is needed to the east since SB-2 does not define the contamination <br /> extent. SB-8-95 defines the lateral and vertical extent (down to 18 feet bgs) southwest of S2. <br /> Definition is needed in the southern section since SB-9-95 does not fully delineate the <br /> contamination. <br /> Response: <br /> 10. Source Area 2 (S2) is the location of a former lampblack pit and a former gas <br /> holder. The lateral and vertical extent of Source Area 2 was determined by data <br /> from the following seven borings: B-2, SB-2, B-17, B-25, SB-7-95, SB-8-95, and SB-9- <br /> 95. In B-25 "oil saturated" soil was noted from 5 to 20 feet bgs. In SB-2, "wood <br /> planking" was noted at about 8 feet bgs,with perched water at 7 feet bgs. In SB-9- <br /> 95, "free water" was noted from 10 to 17 feet bgs. Refusal was encountered in SB-2 <br /> at 8 feet bgs, in SB-7-95 at 22 feet bgs, and in SB-9-95 at 17 feet bgs. B-25 <br /> encountered a hard barrier at 25 feet bgs, but was able to drill to 44.5 feet bgs. The <br /> barrier encountered at 8 feet bgs is most likely the bottom of the former lampblack <br /> pit, and the barrier encountered at 17 and 22 feet bgs is most likely the bottom of the <br /> former gas holder. Chemical data for borings in S2 are summarized in attached <br /> Table 4-3. <br /> The highest total PNA concentration was 9,760 mg/kg in a sample from SB-9-95 <br /> taken from 7.5 feet bgs. PNAs were detected at 22 feet bgs in boring SB-7-95 at a <br /> concentration of 2,165 mg/kg. PNAs were not detected at 30 feet bgs in boring B- <br /> 25, below the apparent bottom of the former gas holder. <br /> The highest concentrations of TPH-gasoline (1,023.1 mg/kg) and total VOCs (44 <br /> mg/kg) in S2 were detected in a sample from B-17 at 10 feet bgs. The highest TPH- <br />