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New Approach to Assess Volatile Contamination in Vadose Zone Provides Path Forward for Site Closure

April 24, 2012 - 12:00pm

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Conceptual site model for evaluating soil vapor extraction system performance to determine
if the system should be optimized, terminated, or transitioned to another approach.

Conceptual site model for evaluating soil vapor extraction system performance to determine if the system should be optimized, terminated, or transitioned to another approach.

RICHLAND, Wash. and LOS ALAMOS, N.M. – Through the Deep Vadose Zone-Applied Field Research Initiative (DVZ-AFRI), scientists and engineers from Pacific Northwest National Laboratory, CH2M HILL Plateau Remediation Company, federal agencies, and the scientific community are collaborating to develop effective, science-based solutions for remediating, characterizing, monitoring, and predicting the behavior and fate of deep vadose zone contamination.

DVZ-AFRI is supported through a memorandum of understanding with EM’s Office of Soil and Groundwater Remediation and the Richland Operations Office. This partnership is maximizing resources to facilitate development of the scientific and technical foundation and technologies needed to make sound and defensible remedial decisions that will successfully meet target cleanup goals.

Soil vapor extraction (SVE) is a baseline remediation approach applied at many sites to remove volatile contaminants from the vadose zone. While SVE generally removes contaminants from most parts of the vadose zone, many sites have low-permeability heterogeneities that limit the ability of SVE remediation and leave residual, persistent zones of contamination. Under these conditions, a risk informed evaluation of SVE performance should determine if the system needs to be optimized, terminated, or transitioned to another approach.

DVZ-AFRI scientists and engineers developed and tested a science-based approach to set appropriate remediation risk-based end states for volatile contaminants in the vadose zone. The approach has been applied at the Hanford Site, and the process defined appropriate remediation goals for an SVE system treating carbon tetrachloride.

At Los Alamos National Laboratory, the approach is being applied to determine whether or not active remediation is needed for identified vadose zone contamination, to establish remediation cleanup levels, and to support the decision-making process with the New Mexico Environmental Department on appropriate remediation goals and monitoring strategies.

National impact of the effort is being further realized through collaboration with DOE, U.S. Environmental Protection Agency, and U.S. Army Corps of Engineers scientists to adapt the approach and provide guidance for defining the end states for other sites with volatile organic contaminants in the vadose zone.

Citation: Wellman DM. 2011. Deep Vadose Zone – Applied Field Research Initiative: Fiscal Year 2011 Annual Report. PNNL-20757, Pacific Northwest National Laboratory, Richland, Washington.

For more information, contact Michael J. Truex, Pacific Northwest National Laboratory, Richland, at mj.truex@pnnl.gov or (509) 371-7072, or Danny Katzman, Los Alamos National Laboratory, Los Alamos, at katzman@lanl.gov or (505) 667-6333.

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