WP1 Restoration of Contaminated Sites
Ballroom E, Level 4
2:10 PM - 5:30 AM, Wednesday, 12 November 2003
Chair: Barnthouse, Larry ,
(411) In situ bioremediation of explosives in the vadose zone.
Radtke, C1, 2, Blackwelder, D1, Crabtree, D3, Thornhill, G3, Rainwater, K3, Roberto, F1, Cobb, G2, 1 Idaho National Engineering and Environmental Laboratory, Idaho Falls, Idaho, USA2 The Institute of Environmental and Human Health, Lubbock, Texas, USA3 Water Resources Center, Lubbock, Texas, USA
ABSTRACT- The Department of Energy (DOE), Department of Defense (DOD), and private companies possess many high explosives contaminated sites across the U.S. At most of these sites, the vadose zone serves as a continuing or potential threat of groundwater contamination. At the Pantex facility, the Risk Reduction Standard 2 (RRS2) for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is 2.6 mg/kg-soil, while the RDX concentration in our field site at Pantex was a mean of 18.2 ppm (22.5 ppm median), necessitating remediation. Due to physical constraints, in situ treatment for the vadose zone soil is needed, and this treatment system is the goal of our studies. Based on promising laboratory studies, we applied nitrogen gas to an approximately 30X30X30ft field site at the Pantex plant to drive the site towards anaerobiasis. The nitrogen initially flowed from the center of a fivespot to the corners (Phase I), then was reversed, flowing from individual corners with extraction in the center (Phase II). After four soil sampling periods of nitrogen treatment, we reconfigured the site to receive about 2000 ppmv isopropyl acetate, n-propyl acetate, and isobutyl acetate in individual corners, with continuing extraction at the center. The soil gas was monitored weekly with 2-L Tedlar bag samples using polyacrylate-SPME subsampling and GC/MS. After 23 weeks n-propyl acetate broke through at a flow distance of approximately 4 ft at a 10 ft depth and averaged a continuing 7.1 ppm, including 42.5 ppm of n-propyl alcohol, and with traces of propaldehyde continuing from week 24. The results of the field site including soil analysis for explosives, as well as the results of a final column study will be presented.
Key words: explosives, remediation, soil, unsaturated