SITE INFORMATION AND CORRESPONDENCE_1993-2003

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Draft Soils FS Memorandum -9- 14 September 1993 DDRW, Sharpe ground water problem will remain after the cleanup of the VOC contamination. The dry wells should be addressed as a SWMU in the comprehensive FS in order to address this issue. Stormwater controls may be appropriately dealt with outside the CERCLA project. 5. PCBs in Sump at Bldg. 186: Polychlorinated biphenyls (PCBs) have recently been reported to be present in a concrete sump containing liquids located north of Bldg. 179 at Bldg. 186. A liquid sample collected from the sump contained PCB at a concentration of 11 mg/1. The hazardous level (STLC) for PCBs is 5 mg/1. The Federal Primary MCL for PCB in groundwater is 0.5 µg/1. No other chemical characterization was performed. This sump was not discussed in the RI Sample Plan or Report. None of the buildings located in the maintenance complex surrounding Bldg. 179 (Bldgs. 181, 186, 197, and 198) were recommended for sampling. This sump should have been evaluated as a SWMU in the RI/FS. The sump is slated for closure, however, sampling will be required to assess possible waste releases and selection of remedial action to close this unit. This new information again brings into question the adequacy of the RI and the recommendation for no further action at many of the sites. OTHER COMMENTS 6. Pesticide Cleanup Levels: The Draft Soils FS fails to clearly identify proposed soil cleanup levels for the various pesticides at DDRW, Sharpe. In addition, the Draft Soils FS did not evaluate potential response actions. The Draft Final FS must provide proposed cleanup levels for the pesticides of concern, including DDD, DDE, DDT, and chlordane (see Major Comment 1 on the use.of the DLM). The proposed response actions for pesticide contaminated soil should also be discussed. This would also apply to PCBs if the sump is included (see Major Comment 5). 7. Air Sparging: The Draft Soils FS does not propose air sparging and duel vacuum as remedial alternatives for the removal of TCE contamination from the vadose zone. Air sparging and dual vacuum in conjunction with vapor extraction have been demonstrated, in certain cases, to be effective in removing VOCs in the vadose zone. It is not clear why air sparging was not included in the original list of remedial alternatives to be screened. These remedial technologies may technically be appropriate, and should be considered for the Sharpe site. SPECIFIC COMMENTS a. Page 1-30, Section 1.3.1.1, Air Contamination: The second paragraph states that TCE was not detected in any sample, nor at the projected point of maximum downwind impact of the South Balloon Area Groundwater Treatment System. The third paragraph states that two occurrences of TCE were found, one each at downwind Stations E17 and K19. These statements are contradictory and no explanation for the occurrence of TCE is provided.