Los Alamos Updates Community on Hexavalent Chromium Campaign

Joel Hebdon, deputy program manager for Environmental Remediation at Newport News Nuclear BWXT-Los Alamos LLC, reviews a map of the hexavalent chromium plume at Los Alamos National Laboratory with an attendee at the Environmental Management Cleanup Forum.

LOS ALAMOS, N.M. — Participants at a recent public forum received an update on the Hexavalent Chromium Campaign from the U.S. Department of Energy’s (DOE) Environmental Management Los Alamos Field Office (EM-LA) and legacy cleanup contractor Newport News Nuclear BWXT-Los Alamos LLC (N3B).

The hexavalent chromium plume was first detected in 2004 in a regional aquifer monitoring well above the New Mexico groundwater standard of 50 micrograms per liter. The plume is currently estimated to be approximately 1 mile long by a half-mile wide beneath Mortandad Canyon and the southern edge of Sandia Canyon at Los Alamos National Laboratory (LANL). There is no immediate threat to human health or the environment.

During a presentation at the Environmental Management Cleanup Forum, groundwater sampling well data showed how operation of EM-LA’s hexavalent chromium plume interim measures system has a positive effect on the plume — and how chromium levels increase when the system is not operating.

Tom Messing, project manager, Chromium and RDX Remediation at Newport News Nuclear BWXT-Los Alamos LLC, discusses operation of the hexavalent chromium plume interim measures with an attendee at the Environmental Management Cleanup Forum.

EM-LA and N3B fielded questions from attendees on the current status of the plume. In November, the New Mexico Environment Department (NMED) directed DOE to cease all injection for the interim measures, and thus cessation of the system operations.

EM-LA has responded to NMED and proposed restarting the interim measures as soon as possible to prevent further migration of the plume beyond the LANL boundary. Additionally, EM-LA has proposed to collaboratively explore and evaluate these operations with NMED after restart with the aim of informed and adaptive operations, consistent with the purpose and scope of the 2016 Compliance Order on Consent, which was modified in 2024.

The interim measures system — approved by NMED in 2015 — consists of several wells to extract water from the plume, treat the water to remove hexavalent chromium and inject the treated water back into the regional aquifer. Injection establishes a hydraulic barrier in the area of injection, helping reduce the plume.

Assistant Secretary of Environmental Management Tim Walsh, center, receives a briefing in Mortandad Canyon on the hexavalent chromium plume at Los Alamos National Laboratory. During a recent visit to northern New Mexico, Walsh toured several sites with the Environmental Management Los Alamos Field Office and cleanup contractor Newport News Nuclear BWXT-Los Alamos LLC to learn about progress for the legacy cleanup mission at the site.

An expert technical review team, jointly convened by EM-LA and NMED, issued the "Independent Review of the Chromium Interim Measures Remediation System in Mortandad Canyon Los Alamos, New Mexico, December 2024” report.

Matthew Tonkin, president and principal hydrogeologist with S.S. Papadopulos & Associates Inc., is a member of that team. He weighed in on the benefits of operating the interim measures system with injection.

“Pump and treat is time-consuming and expensive, but it is the best method for containing the plume and evaluating the results,” Tonkin said. “With stopping the interim measures, we are missing an opportunity to get data to make more progress toward the remedy.”

EM-LA remains committed to advancing efforts to remediate the hexavalent chromium plume. Assistant Secretary of Environmental Management Tim Walsh recently met with Pueblo de San Ildefonso and Los Alamos County leadership to listen to concerns regarding the shutdown of the interim measures system.

-Contributor: Stephanie Gallagher