Monitoring of Subsurface Contaminant Remediation at Moab UMTRA

Monitoring of Subsurface Contaminant Remediation at Moab UMTRA

The Moab Uranium Mill Tailings Remedial Action (UMTRA) site is a former uranium ore-processing facility managed by the U.S. Department of Energy (DOE) in collaboration with Lawrence Berkeley National Lab (LBNL). The highest remediation priority for the site is hauling and disposal of mill tailings. Additional efforts of the site are focused on remediation of a uranium plume on the edge of Colorado river, with the main goal of protecting the river’s ecosystem. The current remediation approach is based on injection of solutions of calcium-citrate and sodium-phosphate into sediments, which leads to citrate biodegradation and formation of hydroxyapatite, which will serve as a permeable reactive barrier, decreasing uranium mobility.

Conventional techniques for monitoring remediation processes use direct sampling of well fluids and soil coring. These manual approaches are labor-intensive, time-consuming, and provide limited temporal and spatial information. An additional drawback is the exposure of technical personnel conducting these measures to radioactive materials and waste disposal.

As part of a DOE-funded Phase 2 SBIR proposal to monitor subsurface contaminant remediation, Vista Clara conducted initial borehole NMR logging within existing 3-inch PVC wells located at UMTRA on the edge on Colorado River. These wells are used for Calcium-Citrate-Phosphate injection and hydroxyapatite precipitation monitoring. The borehole logging was done using a Javelin Slim NMR logging system (2.38” diameter probe). In comparison to conventional methods, Vista Clara NMR logging acquisition and post-processing software enables simultaneous processing and displaying of collected data, thus providing real-time feedback on aquifer properties.

These NMR measurements are non-destructive, non-radiogenic, and provide high-resolution evaluation and visualization of crucial aquifer properties such as water content associated with different porosities, hydraulic conductivity, and transmissivity. Since key aquifer properties are measured in real time, no additional costs associated with off-site consultant processing and review are required.

The DOE and LBNL will use these and future Vista Clara NMR logs at the UMTRA site to plan and monitor injections and remediation progress, boosting the efficiency and lowering the cost of remediation activities at the site.

During the UMTRA site visit, Vista Clara staff also successfully field tested the new Javelin Micro 1.75 inch tool.

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