LAS VEGAS - EM is on pace to make significant strides in contaminated groundwater and soil cleanup in and near the Nevada National Security Site (NNSS) this year.
Groundwater Characterization
Ensuring the public water supply is safe from groundwater contaminated by four decades of underground nuclear testing at the NNSS is a high priority. This is the mission of the Underground Test Area (UGTA) team, whose end goal is transitioning all NNSS areas to long-term monitoring. To accomplish this, NNSS scientists conduct investigations, collect and analyze data, and interpret results used to develop computer models of the subsurface environment.
Using various models of geology, groundwater flow and contaminant movement, scientists can monitor and forecast the location and extent of contamination within thousands of feet of complicated geology hidden beneath the site’s 1,360-square-mile-surface. In accordance with a, data collection and modeling is an iterative process with technical peer reviews built in prior to key decision points.
The peer review process allows NNSS scientists to attain consensus with the scientific community for studies conducted at all groundwater characterization areas. Internal and external peer reviews help ensure uncertainties are sufficiently accounted for, and the model outputs are scientifically defensible.
“It’s not a rubber stamp of approval," UGTA Activity Lead Bill Wilborn said of the peer review process. “There can be a lot of dissent during a peer review, and you have to address that. It’s a very dynamic dialogue."
This process was successfully completed to transition the Frenchman Flat groundwater characterization area to long-term monitoring in 2016. That was Wilborn’s biggest accomplishment after more than 20 years.
“I’m very proud we closed Frenchman Flat," Wilborn said. “This was a significant step forward in our efforts to transition all NNSS groundwater characterization areas into long-term monitoring."
This year, the UGTA team will collect data at three wells drilled in 2016 at the Yucca Flat/Climax Mine groundwater characterization area to improve and refine models. Groundwater samples will be collected and analyzed for tritium in the lower carbonate aquifer. These results will help ensure the models are conservative and protective of public health and safety.
At the Rainier Mesa/Shoshone Mountain groundwater characterization area, EM will move forward with an approved alternative modeling strategy. The strategy calls for generating multiple one-dimensional streamline models of contaminant transport. Concurrently, scientists studying this area are preparing for an external peer review, an important step toward long-term monitoring.
This journey involves a team of federal, contractor, laboratory, and U.S. Geological Survey personnel led by Wilborn, an EM employee since 1991.
Wilborn finds his work unique; he doesn’t know of another program conducting an effort like this. It’s also exciting to interact with scientists across the nation, from DOE’s Los Alamos and Lawrence Livermore national laboratories to the Desert Research Institute, he said. Together, they create EM’s groundwater models to help develop a long-term monitoring network.
Soils Cleanup
Above ground at the NNSS, EM continues to clean up soils contaminated by historic nuclear testing. Closure work begins at the Clean Slate II site this summer, following the successful remediation of the Clean Slate I and Double Tracks sites. These sites were used for plutonium dispersal tests and are located on the neighboring U.S. Air Force-controlled Nevada Test and Training Range, which surrounds the NNSS.
“This year our main focus is the remediation of the Clean Slate II site," said Tiffany Lantow, the /industrial sites activity lead responsible for characterizing and remediating soils, buildings and support facilities contaminated by historic nuclear research and testing. “The primary contaminant at this site is plutonium. We characterized the site last year, meaning we determined the extent of contamination. The area of contamination was smaller than anticipated, so it’s feasible to clean and close that site this year."
Lantow counts the Clean Slate I and Double Tracks projects, conducted in collaboration with the Air Force, among her most significant recent work accomplishments. Those sites were closed in accordance with the.
“This is a huge accomplishment for us," she said of the closures. “The completion of both projects came after decades of study and required collaboration across multiple state and federal agencies," Lantow said.
To prepare for another successful closure, workers will excavate, package and transport radioactive soils and debris from Clean Slate II for disposal at the NNSS.
EM is investigating the nature and extent of contamination at Clean Slate III, another plutonium dispersal test site. EM employees are also conducting investigations and remediating contaminated historic atmospheric test sites on the NNSS. This work, and approval of the final closure reports, moves the project one step closer to completion, which is slated for 2020.
Currently, the project is 82 percent complete, which is a good feeling for Lantow, who joined EM in 2007 after working as an environmental scientist with a partner agency for 10 years.
“I’m proud of our team," she said. “We are dedicated to ensuring remediation is accomplished in a manner that is protective of human health and the environment using a cost-effective approach."
Source: U.S. Dept. of Energy, Office of Environmental Management
