The U.S. Department of Energy Environmental Management Los Alamos Field Office remains dedicated to remediating the hexavalent chromium plume at Los Alamos National Laboratory.
Office of Environmental Management
June 25, 2026
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LOS ALAMOS, N.M., June 25, 2026 – The U.S. Department of Energy (DOE) Environmental Management Los Alamos Field Office (EM-LA) remains dedicated to remediating the hexavalent chromium plume at Los Alamos National Laboratory (LANL). Since discovering the plume in 2004, DOE has worked with the New Mexico Environment Department (NMED) to install a network of wells to characterize the plume, and a water treatment system to treat hexavalent chromium. In 2015, NMED approved the chromium interim measures (IM).
In accordance with the 2016 Compliance Order on Consent (Consent Order), the purpose of the IM is to reduce or prevent migration of the hexavalent chromium plume that may result in an unacceptable human or environmental receptor risk while long-term corrective action activities are evaluated and implemented.
On March 31, 2023, EM-LA shut down the IM based on NMED’s direction to cease injection by April 1, 2023. Given the design of the IM and limitation of alternative water discharge options, ceasing injection under the IM necessarily drives cessation of all IM operations.
In September 2024, EM-LA restarted the IM system, in alignment with NMED and after adjusting extraction and injection rates to mitigate concerns associated with full operation.
On November 18, 2025, NMED directed EM-LA to “immediately cease all injection operations associated with the IM system,” which necessitated IM shutdown. This is the second shutdown of the IM operations to comply with NMED’s direction. Since April 2023, the IM has operated for only 14 months.
Groundwater well sampling data shows that the IM has a positive effect: injection establishes a hydraulic barrier in the area of injection, which helps to control and reduce the plume, while also preserving aquifer water, a precious natural resource. During the first and second IM shutdowns per NMED’s direction, EM-LA observed increases in hexavalent chromium concentration in most monitoring wells within the first few months. EM-LA and NMED agree that there is no immediate threat to public or private drinking water wells.
Operation of a Partial IM is Essential
Operating the IM in a partial configuration supports the purpose of the IM and enables adaptation based on new data. This is consistent with the Chromium Expert Technical Review team’s conclusion in its December 2024 final report, “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.”
EM-LA proposed to collaboratively explore and evaluate IM operations with NMED after the IM restart in September 2024, with the aim of informed and adaptive operations for a more effective IM. EM-LA continues to collaborate with NMED, the New Mexico Office of the State Engineer, Pueblo de San Ildefonso, and Los Alamos County.
NMED has sought to require land application of up to 35 million gallons of treated water each year as an alternative to the IM’s injection wells while alternative water disposition methods are evaluated and implemented. Such a requirement to land apply treated water versus returning treated water to the regional aquifer is not a responsible use of water—a precious resource in New Mexico. Permit conditions limit land application operations and would mine the regional aquifer. While EM-LA intends to retain the option to land apply as a contingency for managing the water, the IM should return the water to the regional aquifer to preserve this precious resource.
EM-LA and its legacy cleanup contractor, Newport News Nuclear BWXT-Los Alamos, LLC, have reengaged subject matter experts from the Independent Technical Review to evaluate new data since the 2024 review in the context of the current configuration of the IM and operations, and assess opportunities to optimize the IM based on new data. These experts include Ines Triay, executive director of the Applied Research Center at Florida International University, and Matthew Tonkin, president and principal hydrogeologist, S.S. Papadopulos & Associates, Inc.
“From our perspective, the Independent Technical Review recommendation to partially operate the interim measures remains; IM operations with injection should resume as soon as possible. With stopping the IM, we are missing an opportunity to get data to make more progress toward the final remedy,” stated Triay and Tonkin. “This is an interim remedy for a very complex problem and it is difficult to know everything now. The independent team looked at many options, including alternate water disposition. Our conclusion was the IM should be exercised.”
Chromium Expert Technical Review Recommendations
EM-LA is committed to following the December 2024 report recommendations. To date, EM-LA has:
• Restarted the chromium IM (September 2024), until NMED directed EM-LA to cease injection in November 2025
• Completed monitoring well San Ildefonso Mortandad Regional 3
• Started installing data gap monitoring well R-80
• Continued planning for monitoring well R-79 EM-LA has also begun:
• Evaluating the site conceptual model
• Evaluating an alternative injection well location and design
• Planning for implementation of adaptive management
• Evaluating transition of groundwater modeling software from the Finite Element Heat and Mass transfer model (FEHM) to the USGS Modular Flow (MODFLOW) Model
Media Contact
Stephanie Gallagher
stephanie.gallagher@em.doe.gov
505.257.8563
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