Bench-scale laboratory tests and single well injection pilot tests were conducted in 2000 at two locations. Subsequently, a large scale pilot test was conducted to treat a 12-acre portion of one of the former solvent disposal sites. Injection techniques and monitoring methods were optimized based on earlier pilot tests, resulting in increased efficiency and cost savings.
During the period 2004 through 2006, a second large-scale pilot test was conducted to treat a 21-acre portion of another former solvent disposal location. TCE concentrations dropped below the detection limit in most wells during both large-scale pilot tests, followed by some rebound. However, post-test TCE concentrations in groundwater remain significantly below pre-test concentrations at both sites.
Important differences between ISCO tests at previous sites and testing conducted at AFP-44 include the lower levels of aqueous phase TCE, larger depth of contamination, and increased heterogeneity of the aquifer materials present at AFP-44, as well as the ISCO application methods employed at the site. Low organic carbon content of the alluvial aquifer material is believed to have been a factor in program success. Based on experience at AFP-44, ISCO using potassium permanganate is a cost effective method for destruction of residual TCE in deep, low organic content, desert aquifers.