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8737699 
Meetings & Symposia 
Chemical oxidation of contaminated vadose zone soils using in situ soil mixing 
Kelley, R; Davis, D 
2009 
English 
Significant concerns about indoor air quality have resulted in a greater need for treating contaminated vadose zone soils to lower cleanup goals. In addition, concerns about vadose contamination serving as a long-term feedstock for dissolved phase groundwater contamination has contributed to greater emphasis on more aggressive treatment of contaminated vadose zone soils. Historically, treatment of contaminated soils in the vadose zone has proven expensive and problematic for a myriad of technical issues. This presentation will provide field-scale data from multiple sites that demonstrates cost-effective in situ chemical oxidation (ISCO) treatment of contaminated vadose zone soils using in situ soil mixing techniques. Historically, in situ treatment of vadose zone soils via ISCO often involves flooding the treatment area with large volumes of aqueous treatment amendments. This application approach is difficult to ensure proper contact between the treatment amendment and all contaminants. In situ injection also requires tight hydraulic containment to the potential mobilization of contaminants to the underlying saturated zone prior to oxidation. As a result, practitioners have relied on physical methods to remediate contaminated vadose zone soils, such as soil vapor extraction (SVE) or dig-and-haul. However, because of increasing transportation costs, dumping fees and persistent liabilities, the demand for innovative ISCO methods for both ex situ and in situ treatment of contaminated vadose zone soils is growing significantly. In situ soil mixing with specialized auger application equipment has been shown to be an effective method. With in situ soil mixing, chemical treatment can be cost-effective and completed in short time periods. Several full scale studies have been conducted to evaluate the technical and economic feasibility of in situ chemical oxidation for vadose soil remediation. Several case studies will be discussed in detail. These studies involve treating soils contaminated with chlorinated and petroleum hydrocarbons. The soils tested varied from sand, silt sand to clays. The soil mixing equipment used included simple back hoes, and specialized in situ mixing equipment. Degradation efficiency ranged from 45 -95%, typically in less than 14 days. This presentation will provide an overview of the results from these field demonstrations, draw conclusions for the applicability of the technology for vadose zone contaminated soil remediation and provide recommendations for a best-practice approach for future work. In addition, the presentation will include lessons learned to screen future sites for technology selection.