Field Demonstration/Validation of Electrolytic Reactive Barriers for Energetic Compounds at Pueblo Chemical Depot

Electrolytic reactive barriers (e-barrier) are founded on the principles of a permeable reactive barrier (PRB). Contaminants are carried through the reactive barrier via the natural flow of groundwater. Within the barrier, contaminants are degraded as they pass through titanium screen electrodes charged with low voltage DC current. Contaminants are sequentially exposed to electrolytic oxidation -> reduction -> oxidation -> reduction. The primary appeal of e-barriers has been the low power cost (cents/day/m(2)) and the potential to address contaminants that might otherwise be difficult to treat with existing technologies. An e-barrier demonstration was conducted at Pueblo Chemical Depot (PCD), CO. Historical activity at PCD included demilitarization of expired munitions via washout operations conducted at Solid Waste Management Unit 17 (SWMU-17). Former washout ponds created groundwater plumes containing elevated concentrations of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and other energetic compounds extending thousands of feet beyond the release area. In 1998, sediments associated with the former washout ponds were removed by excavation. Despite source excavation, the remaining soils are sustaining concentrations of RDX; octahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocane (HMX); 2,4-dinitrotoluene (2,4-DNT); 2,4,6-trinitrotoluene (TNT); and 1,3,5-trinitrobenzene (1,3,5-TNB) in groundwater. The e-barrier was located between two former washout ponds. Between 12 and 15 ft of sandy alluvium was encountered above the regionally extensive Pierre Shale formation. Groundwater was encountered in the lower 5 to 7 ft of the alluvium. The average groundwater Darcy velocity was 250 ft/yr. Concentrations of RDX in groundwater have dropped from historic highs of approx. 400 micrograms/L to current levels of <10 micrograms/L.

The original document contains color images. Prepared in cooperation with Colorado State University, Fort Collins, CO.