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Final B-20 Soil Stabilization/Solidification Treatability Study Report
Section 6 - Recommendations
A recommendation for further evaluation of S/S of soils at CSSA, if pursued, is the use of phosphate-based stabilization in order to treat soils with high levels of metallic lead concentrations such as those that existed at the small arms ammunition disposal site within SWMU B-20. Phosphate immobilizes only soluble lead compounds; therefore a key issue to be resolved with phosphate-based immobilization is the concern that elemental lead may serve as a continuing source of leachable lead.
The small arms ammunition disposal site located at B-20 was also the subject of another treatability study using soil washing techniques (Brice, 1998) to remove particulate lead from the soil matrix. Results of this study found that removal of the particulate lead alone did not result in the soil achieving non-hazardous levels of leachable lead (<5.0 mg/kg). The use of S/S in conjunction with soil washing may result in favorable treatment of soil below TNRCC non-hazardous levels for disposal within an off-site municipal landfill.
Should these two technologies be combined to form a treatment train, density treatment of the soils would be performed first, removing most of the particulate lead from the larger and middle soil fractions. After density treatment, the majority of lead contamination would exist in the small soil fractions. The use of density treatment prior to S/S reduces the amount of soil to be stabilized. This soil would be more homogenous and may lend itself to stabilization. These soils would be stabilized, then cure for approximately 30 days prior to disposal at a municipal landfill as non-hazardous waste. Soil recovered from density treatment (mostly from the larger soil fractions) with TCLP lead concentrations less than 5 mg/l may be returned to the original site and backfilled along with clean fill.