SITE INFORMATION AND CORRESPONDENCE_1993-2003

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Draft Soils FS Memorandum -13- 14 September 1993 DDRW, Sharpe 3B-Innovative--Chemical Extraction/Soil Washing: See above comment above. For this type of technology, bench scale testing is also necessary to demonstrate the effectiveness as a remedial alternative prior to selection. For cases where the contaminants are associated with the fine size fraction, the amount of silt and clay (i.e. the weight of soil passing through a No. 200 sieve) should not exceed 20 - 30% in order to achieve an economic volume reduction. The fraction of soil humic content must also be considered (VISITT, EPA 542-R-93-001, No. 2, April 1993). Other issues to consider include: 1. Excessive volume of leaching medium required for contaminants with unfavorable separation coefficients. 2. Fine soil particles (e.g., silts and clays) are difficult to remove from washing fluid. An additional treatment step may be required to remove fines from the process wash water. 3. Additional treatment steps may be required to address hazardous levels of washing solvent remaining in the treated residuals. It is important that the washing solvent have good treatability characteristics (Remedial Technologies Applications Matrix For Base Closure Activities, CA Military Base Closure Environmental Committee, April 1993). 4A-Removal and Disposal--Offsite Landfill Disposal: This alternative is acceptable, however, it does not provide for a permanent solution, but instead transfers the contaminated soil to another location where it would no longer threaten water quality. Therefore, offsite disposal for all potential contamination is not a preferred alternative. 5A-No Action--Limit Access/Use Restrictions: This alternative is unacceptable as it will not fully protect human health or the environment, including water quality. Alternatives for TCE Contaminated Soil 2B-Treatment--Onsite Incineration: This alternative is acceptable, however, there is currently an EPA moratorium on incinerator permits. Other issues to consider include: 1. Toxic metals, either pure or as oxides, hydroxides or salts that volatilize at high temperature (e.g., Cd, As, Hg, Pb, Sit, Ag) may vaporize during incineration and are difficult to remove using conventional air pollution control equipment. Additionally, an element such as trivalent chromium (Cr+3) may be oxidized to a more toxic valence state (e.g., Cr+3 to Cr+6) in combustion systems with oxidizing atmospheres. 2. High temperature thermal technologies do not treat wastes containing heavy metals. Thermal treatment of these wastes can result in higher total and/or soluble metal concentrations in the treatment residuals than in the original wastes (Remedial Technologies Applications Matrix For Base Closure Activities, CA Military Base Closure Environmental Committee, April 1993).