SITE INFORMATION AND CORRESPONDENCE 1995-2004

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Mr. Fernando Amador -4- 14 December 1995 10. Pages 4-6 and 4-10, Section 4.2.1.2, Potential Source Area 2 (S2) The inconsistent sampling program observed in S 1 also is evident in S2. SB-2 was sampled to a maximum depth of only eight feet bgs. Consequently, in spite of detecting 6,234 mg/kg total PNAs and 64 mg/kg total VOCs at eight feet bgs, no additional data are available. Furthermore, TPHd and TPHg were not analyzed in the sample. The sampling protocol used in MW-9 also was used in B-17, resulting in lack of information beyond 16.4 feet bgs where total PNAs and TPHd were detected at 1,700 mg/kg and 1,574 mg/kg, respectively. SB-7-95, which was sampled at a maximum depth of 22 feet bgs, had 2,165 mg/kg total PNAs, 27 mg/kg total VOCs, 380 mg/kg TPHg, and 9,900 mg/kg TPHd. Thus, the lateral and vertical extent of contamination to the north has not been defined. B-17 which is the westernmost sample location, also does not define the contamination to the west. Definition also is needed to the east since SB-2 does not define the contamination extent. SB-8-95 defines the lateral and vertical extent(down to 18 feet bgs) southwest of S2. Definition is needed in the southern section since SB-9-95 does not fully delineate the contamination. 11. Page 4-10, Section 4.2.1.3, Potential Source Area 3 (S3) The FS states that S3 is characterized by B-15, SB-19-95, SB-20-95, MW-3, and B-13. SB-20-95 defines the lateral and vertical extent to the north. To the south, B-15 shows high contaminant concentrations between 3.5 and eight feet bgs and residual contaminants at about 17 and 21 feet bgs. The lateral extent has not been defined, but the vertical extent is defined at about 26 feet bgs. To the east, SB-19-95 defines the lateral extent but not the vertical extent since all the contaminants had the highest concentrations at the deepest sampling point of 16 feet bgs. There is no information to the west at or near the S3 boundary and, therefore, requires lateral and vertical definition. 12. Page 4-12, Section 4.2.1.4, Potential Source Area 4 (S4) The FS states that borings MW-10, MW-6, MW-8, MW-18, B-9, B-11, SB-13-95, SB-14-95, and SB-13-95 characterize S4. MW-10 is the northernmost sample location. Due to the high concentrations of total PNAs and TPHd at seven feet bgs, further lateral definition is needed in this area and also to the northwest where no data are available. SB-16-95 should be used to approximate the lateral and vertical limit of contamination to the east, instead of estimating the limit as being between SB-15-95 and SB-16-95. To the southwest, SB-13-95 had 2.4 mg/kg of total PNAs, but it was only sampled at four feet bgs. To the southeast, SB-14-95 was sampled only at 20 feet bgs and had high concentrations of total PNAs and TPHd and detections of total VOCs and TPHg. Therefore, further lateral and vertical definition is needed in the southern section of S4.