SITE INFORMATION AND CORRESPONDENCE 1995-2004

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0 0 James L. Tjosvold, P.E. August 19, 1996 Page 22 Soil samples from SB-1-95 and B-16 indicated elevated concentrations of PNAs and TPH-diesel in near-surface samples but not in deeper samples. In SB-1-95, PNAs and TPH-diesel were detected at 3.5 feet bgs at levels of 736 and 980 mg/kg, respectively,with lower concentrations below this depth. In B-16, PNAs and TPH- diesel were detected at 478.2 and 1,036 mg/kg, respectively, at 2.0 feet bgs, but not below this depth. TPH-gasoline was detected in B-16 at 823 mg/kg at 21 feet bgs. In SB-1B and B-1, PNAs were present near the surface at 609 and 216 mg/kg, respectively, and decrease significantly with depth. BTEX were also present, but no data on TPH-gasoline or TPH-diesel were collected. SB-21-95 contained elevated levels of PNAs (456 mg/kg) and TPH-diesel (1,500 mg/kg) at 3.5 feet bgs. Deeper samples contained very low concentrations of these constituents. The adjacent boring SB-22-95 contained low levels of PNAs and TPH- diesel at 3.5 and 7.5 feet bgs. B-14, in the general vicinity of SB-21-95 and SB-22-95 contained PNAs at 1,381 mg/kg and TPH-diesel at 7,270 mg/kg at 3 feet bgs. Deeper sample contained much lower levels. MW-4, B-26, and B-2 are in the center of the property. PNAs were detected in MW- 4 at 514 mg/kg in a sample between 0 and 3 feet bgs, but not below. In samples from B-26 and B-2, total PNA concentrations were less than 10 mg/kg. BTEX were detected in MW-4 at 32 mg/kg at 43 to 48 feet bgs. TPH-gasoline and TPH-diesel were detected in a soil sample from B-26 at 20.5 feet bgs at concentrations of 129.3 and 509 mg/kg, respectively. Comment: C. Southern Third The FS should explain the rationale for the inconsistent sampling depths. For example, SB-5- 95 was sampled only at about five and 25 feet bgs, SB-6-95 was sampled only at four and 23 feet bgs, etc. Lateral definition is needed at B-7. The FS should explain why B-13, B-7, B-8,; B-12, and B- 10 were not tested for TPHd/g. The lateral and vertical extent of the contamination at B-7 should be defined. Response: The borings in the southern third of the site are: SB-5-95, SB-6-95, B-13, B-7, B-8, SB- 10-95, SB-11-95, B-18, SB-24-95, SB-12-94, MW-7, B-12, and B-10. (No soil samples were collected from MW-1R, MW-11), or MW-11.) PNAs were detected at 1,246 mg/kg in B-7 between 0 and 3 feet bgs and no PNAs were detected below this depth. Total PNA concentrations in all other boring samples ranged from non-detect to 18 mg/kg.