Multiple Tracer Testing Approaches for Improved Groundwater Flow and Reactive Transport Modeling Input Parameters

Monday, December 4, 2017: 11:30 a.m.
101 C (Music City Center)
Raymond Johnson, Ph.D. , Navarro Research and Engineering, Inc., Grand Junction, CO
Paul Reimus, Ph.D. , Los Alamos National Laboratory, Los Alamos, NM
Aaron Tigar , Navarro Research and Engineering, Inc., Grand Junction, CO
Sarah Morris , Navarro Research and Engineering, Inc., Grand Junction, CO
Kara Tafoya , Navarro Research and Engineering, Inc., Grand Junction, CO
William Dam , U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
William Frazier , U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
Richard Bush , U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
Sam Campbell , Navarro Research and Engineering, Inc., Grand Junction, CO

At many U.S. Department of Energy Office of Legacy Management (LM) uranium mill tailings sites, initial groundwater flow and solute transport modeling was completed 20–25 years ago using field data that included hydraulic head information and a few aquifer pumping tests. Because the uranium tailings were either removed or placed in capped disposal cells, and the simulations assumed limited uranium sorption, these models did not consider ongoing uranium contaminant sources. Currently, several sites have uranium concentrations that exceed the prior model predictions, which has led to the identification of uranium sources in the subsurface that were not previously identified. In order to update the past models, tracer testing techniques are being considered to provide more accurate information on groundwater flow velocities, flow directions, ongoing uranium sources, uranium sorption potential, and dual-porosity issues related to aquifer grain coatings and cements.

Tracer testing will be completed in the summer or fall of 2017 using multiple tracers and techniques at LM’s Grand Junction, Colorado, Site, which is located on a shallow alluvial aquifer adjacent to the Gunnison River. This tracer testing will include the use of borehole dilution, push-pull, and cross-hole techniques that focus on identified areas with elevated solid-phase uranium concentrations. The test data will be analyzed to estimate groundwater flow directions, velocities, and uranium transport parameters (sorption and dual-porosity influences) and be compared to previous estimates. This presentation will discuss how these multiple tracer tests were completed, interpreted, and then used to provide updated input parameters for revising the site groundwater flow and reactive transport models (conceptual and numerical).

Raymond Johnson, Ph.D., Navarro Research and Engineering, Inc., Grand Junction, CO
Dr. Johnson is a geochemist/contaminant hydrogeologist with Navarro Research and Engineering, a contractor for the U.S. Department of Energy Office of Legacy Management. He has 12 years of experience working on reactive transport of uranium in legacy groundwater plumes and predictive modeling of uranium transport related to uranium in situ recovery sites. Much of his prior 15 years of experience in contaminant hydrogeology were related to metal transport in groundwater around areas with abandoned mine lands. He has been in his current position as a contractor for the U.S. Department of Energy for 3 years and was with the U.S. Geological Survey in Denver, Colorado for the prior 12 years.


Paul Reimus, Ph.D., Los Alamos National Laboratory, Los Alamos, NM
Dr. Paul Reimus is a geochemist/hydrogeologist at Los Alamos National Laboratory with expertise in groundwater tracer testing.


Aaron Tigar, Navarro Research and Engineering, Inc., Grand Junction, CO
Aaron Tigar is a research assistant with Navarro Research and Engineering, Inc.(contractor to the U.S. Department of Energy Office of Legacy Management)


Sarah Morris, Navarro Research and Engineering, Inc., Grand Junction, CO
Sarah Morris is a chemist with Navarro Research and Engineering (contractor to the U.S. Department of Energy Office of Legacy Management).


Kara Tafoya, Navarro Research and Engineering, Inc., Grand Junction, CO
Kara Tafoya is a laboratory technician with Navarro Research and Engineering, Inc.(contractor to the U.S. Department of Energy Office of Legacy Management).


William Dam, U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
William Dam is a hydrologist/site manager for the U.S. Department of Energy Office of Legacy Management.


William Frazier, U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
William Frazier is a site manage for the U.S. Department of Energy Office of Legacy Management.


Richard Bush, U.S. Department of Energy Office of Legacy Management, Grand Junction, CO
Richard Bush is the UMTRCA Program Manager for the U.S. Department of Energy Office of Legacy Management.


Sam Campbell, Navarro Research and Engineering, Inc., Grand Junction, CO
Sam Campbell is a site lead and the manager of the environmental monitoring operations for Navarro Research and Engineering, Inc.(contractor to the U.S. Department of Energy Office of Legacy Management)


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