Evapotranspiration And Geochemical Controls On Groundwater Plumes At Arid Sites: Toward Innovative Alternate End-States For Uranium Processing And Tailings Facilities
Management of legacy tailings/waste and groundwater contamination are ongoing at the former uranium milling site in Tuba City AZ. The tailings have been consolidated and effectively isolated using an engineered cover system. For the existing groundwater plume, a system of recovery wells extracts contaminated groundwater for treatment using an advanced distillation process. The ten years of pump and treat (P&T) operations have had minimal impact on the contaminant plume – primarily due to geochemical and hydrological limits. A flow net analysis demonstrates that groundwater contamination beneath the former processing site flows in the uppermost portion of the aquifer and exits the groundwater as the plume transits into and beneath a lower terrace in the landscape. The evaluation indicates that contaminated water will not reach Moenkopi Wash, a locally important stream. Instead, shallow groundwater in arid settings such as Tuba City is transferred into the vadose zone and atmosphere via evaporation, transpiration and diffuse seepage. The dissolved constituents are projected to precipitate and accumulate as minerals such as calcite and gypsum in the deep vadose zone (near the capillary fringe), around the roots of phreatophyte plants, and near seeps. The natural hydrologic and geochemical controls common in arid environments such as Tuba City work together to limit the size of the groundwater plume, to naturally attenuate and detoxify groundwater contaminants, and to reduce risks to humans, livestock and the environment. The technical evaluation supports an alternative beneficial reuse (“brownfield”) scenario for Tuba City. This alternative approach would have low risks, similar to the current P&T scenario, but would eliminate the energy and expense associated with the active treatment and convert the former uranium processing site into a resource for future employment of local citizens and ongoing benefit to the Native American Nations.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE (United States)
- DOE Contract Number:
- DE-AC09-08SR22470
- OSTI ID:
- 1122793
- Report Number(s):
- SRNL-STI-2014-00013; TRN: US1400299
- Resource Relation:
- Conference: WM2014 Conference, Phoenix, Arizona (United States), 2-6 Mar 2014
- Country of Publication:
- United States
- Language:
- English
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