The U.S. Department of Energy (DOE) Environmental Management Los Alamos Field Office (EM-LA) remains committed to remediating the hexavalent chromium plume at Los Alamos National Laboratory (LANL). EM-LA continues to proactively assess, monitor, and collaborate with the New Mexico Environment Department (NMED), the New Mexico Office of the State Engineer, Pueblo de San Ildefonso, and Los Alamos County to complete this objective.
Since 2004, DOE has worked collaboratively with NMED to install a network of wells to characterize the plume, and a water treatment system to remove hexavalent chromium from the regional aquifer.
EM-LA agrees with NMED that the plume is not currently near known public or private drinking water wells. The safety of workers, the public, and the environment is EM-LA’s top priority.
On November 18, 2025, NMED directed EM-LA to cease all injection operations for the Hexavalent Chromium Plume Control Interim Measures (IM).
In response to NMED’s letter, EM-LA immediately turned off the Chromium IM system, which is intended to prevent further migration of the plume from LANL. On November 21, EM-LA responded and proposed collaborating with NMED to restart the IM as soon as possible to avoid increasing chromium concentrations near the LANL/Pueblo de San Ildefonso boundary, which was observed following shutdown of the IM in March 2023 to September 2024.
EM-LA resumed partial operation of the Chromium IM in September 2024 in alignment with NMED’s authorization, and consistent with the Expert Technical Review Team’s recommendation. The final report by the Expert Technical Review Team concluded, “The single most important recommendation … is to restart the IM—using a portion of the original system—while other studies and field investigations move forward.”
For details on the collaboration with NMED, please visit https://www.env.nm.gov/hazardous-waste/chromium-groundwater-contamination/.
EM-LA’s top environmental remediation project is the hexavalent chromium plume in Mortandad and Sandia Canyons at Los Alamos National Laboratory (LANL). The primary source of the plume was a non-nuclear power plant at LANL that periodically flushed coolant water containing potassium dichromate from the plant’s cooling towers into Sandia Canyon from 1956-1972. Potassium dichromate (the primary contaminant of concern is hexavalent chromium) was a permitted effluent used as a descaling agent in power plants worldwide during this time. Up to 160,000 lbs. of hexavalent chromium was released from the cooling towers, a small portion of which migrated into the regional aquifer.
Current measurements indicate the plume is approximately one mile long by half a mile wide. The primary objective of Chromium Plume Control Interim Measures (IM) under the 2016 Compliance Order on Consent, as revised in 2024 (Consent Order) between the U.S. Department of Energy and the New Mexico Environment Department (NMED) is to prevent migration of the hexavalent chromium plume beyond the LANL boundary.
On March 30, 2023, EM-LA shut down operation of the IM as a result of complying with NMED’s direction to cease injection by April 1, 2023.
In August 2023, EM-LA and NMED received a recommendation from the Radioactive and Hazardous Materials Committee of the New Mexico Legislature to engage in a third-party review regarding the IM. In December 2023, EM-LA and NMED requested Dr. Ines Triay, Interim Dean, College of Engineering and Computing, and the Executive Director for the Applied Research Center, Florida International University, to organize and conduct an independent technical review of actions taken by EM-LA to characterize and model the hexavalent chromium plume at LANL, and the efficacy of the IM taken to prevent plume migration offsite.
In March 2024, EM-LA and NMED convened a team of experts from the Network of National Laboratories for Environmental Management and Stewardship, industry, academia, and EPA Region 6 to perform a technical review and help facilitate a technical discussion and resolution of EM-LA and NMED’s differing professional opinions.
Prior to finalization of the report, EM-LA worked together with NMED to resume partial operation of the Chromium IM on September 30, 2024.
The Hexavalent Chromium Project Expert Technical Review Team has issued the Independent Review of the Chromium Interim Measures Remediation System in Mortandad Canyon Los Alamos, New Mexico, December 2024 report.