Contaminants, Compliance, and Caveats: Field Studies at DOE's Rifle Integrated Field Research Challenge (IFRC) site
THURSDAY OCTOBER 17, 2013 - 2:00 PM, DC 1304
The Department of Energy’s Integrated Field Research Challenge site (IFRC) at Rifle, Colorado (USA) overlies a shallow alluvial aquifer adjacent to the Colorado River contaminated with uranium, vanadium, arsenic, and selenium from former milling activities. Groundwater monitoring over the past decade shows varying patterns of dissolved metals behavior, with significant deviations in aqueous U, V, As, and Se associated with seasonal variations in water level and organic carbon addition. A key challenge at the site is unraveling the myriad biogeochemical and hydrological processes that control contaminant mobility and impede natural flushing – the approved compliance strategy for achieving contaminant levels at or below regulatory standards. This talk highlights a variety of issues that remain to be addressed before one or more sustainable remediation approaches can be implemented at sites contaminated with radionuclides and redox-sensitive metals. Examples include variations in the solubility of such contaminants under changing redox conditions, the long-term stability of immobilized contaminants, hydrological impacts resulting from biomass and mineral accumulation, and the contribution of contaminant fluxes from off-site locations. Data to be considered include geochemical, hydrological, isotopic, and microbiological. Assessing the extent to which active (i.e., engineered) and passive (i.e., natural) attenuation mechanisms can be incorporated into compliance strategies is a key outcome of the research activities at the Rifle IFRC site, as is refinement of remediation approaches to enhance their prolonged efficacy.