sampling activities at a well on Pahute Mesa at the NNSS

EM Nevada receives key regulatory approval for last active groundwater area

sampling activities at a well on Pahute Mesa at the NNSS
EM Nevada Program sampling activities at a groundwater characterization well on Pahute Mesa at the Nevada National Security Site.

The U.S. Department of Energy (DOE) Environmental Management (EM) Nevada Program has earned a key regulatory approval necessary to advance its groundwater environmental corrective mission at the Nevada National Security Site(NNSS). The milestone — approval of “data completeness” — was granted by the Nevada Division of Environmental Protection (NDEP). The approval paves the way for EM Nevada to continue scientific study at Pahute Mesa, the fourth and final active groundwater corrective action area at the NNSS.

Under the Federal Facility Agreement and Consent Order (FFACO) — a regulatory agreement governing EM cleanup approaches at the NNSS — an assessment of “data completeness” comes after the collection and analysis of field data and before the start of advanced scientific modeling to support groundwater corrective actions. The data collected by EM Nevada, analyzed by technical experts, and reviewed by NDEP includes information related to groundwater chemistry, pressure levels, subsurface temperature, and geologic properties.

With initial data collection and analysis complete, experts have begun developing sophisticated scientific models to forecast where and how contamination might move within the groundwater under Pahute Mesa. Much of the technical work associated with this process, known broadly as characterization, is conducted by Navarro Research and Engineering, Inc., the environmental services contractor to EM Nevada.

“Approval of data completeness is a key accomplishment that will allow our program to continue advancing our groundwater strategy at Pahute Mesa,” said Rob Boehlecke, EM Nevada Program manager. “As always, I thank the Nevada Division of Environmental Protection for their partnership and collaboration. I also want to recognize our collaborating partners with the United States Geological Survey, contractors Navarro and Mission Support and Test Services, and the Desert Research Institute, who are all helping to facilitate the safe, secure, and successful completion of our overall groundwater mission by 2028.”

Groundwater contamination at the NNSS is the result of historical underground nuclear testing conducted from 1951 to 1992. To date, EM Nevada has succeeded in transitioning three of four main groundwater regions at the NNSS to long-term monitoring, with only Pahute Mesa remaining in the corrective action investigation stage. Decades of testing, analysis, and modeling have resulted in an extensive understanding of the nature and movement of groundwater under the NNSS. As a result, current research shows that contaminated groundwater will not reach public water supplies.

EM Nevada projects that the Pahute Mesa groundwater corrective action region will transition to long-term monitoring by 2028. Regulatory closure of the Pahute Mesa groundwater area will complete EM’s environmental restoration mission in Nevada.