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Application Of Monitored Natural Attenuation For Cleanup Of Radionuclides In Groundwater
Citation:
FORD, R. G. Application Of Monitored Natural Attenuation For Cleanup Of Radionuclides In Groundwater. Presented at 10th Superfund National Radiation Meeting, Albuquerque, NM, March 30 - April 03, 2009.
Impact/Purpose:
The lessons learned from a retrospective analysis (evaluation of the unsuccessful performance of an MNA remedy for uranium contamination in groundwater at a Superfund site in Richland, Washington) will be compared to technical recommendations that have recently been proposed to establish a consistent framework under CERCLA for evaluating the suitability of Monitored Natural Attenuation (MNA) as a component of the remedy for restoration of groundwater contaminated with radionuclides.
Description:
A retrospective analysis was conducted to evaluate the unsuccessful performance of an MNA remedy for uranium contamination in groundwater at a Superfund site in Richland, Washington. The primary factors that limited the accuracy of contaminant transport model projections at this site was an inadequate characterization of the impact of temporal variations in groundwater hydrology and chemistry, along with an incomplete characterization of residual contamination in the vadose zone. Both factors contributed to greater flux of uranium through the saturated aquifer over that predictd by the contaminant transport model. Additional efforts to characterize the dynamics of the hydrologic system, the distribution and characteristics of residual uranium contamination in vadose soils, and identification of the chemical factors controlling uranium transport in groundwater have resulted in a more accurate Conceptual Site Model and, ultimately, the evaluation of in-situ technologies to control uranium release from residual source areas. The lessons learned from this retrospective analysis will be compared to technical recommendations that have recently been proposed to establish a consistent framework under CERCLA for evaluating the suitability of Monitored Natural Attenuation (MNA) as a component of the remedy for restoration of groundwater contaminated with radionuclides. These recommendations outline approaches to assess the role of radioactive decay and immobilization for attenuation of radionuclides within a groundwater plume. This is an abstract of a propsed presentation and does not necessarily reflect EPA policy.