BY MAIRE O’NEILL
maire@losalamosreporter.com
Officials from the New Mexico Environment Department will attend the Los Alamos Board of Utilities Wednesday March 4 Work Session in Council Chambers at the Municipal Building at 5:30 p.m.
Michael Petersen, MS, a hydrogeologist with NMED, and Caitlin Martinez, acting NMED LANL Group Manager will make a presentation on the San Ildefonso Mortandad Regional 3 (SIMR-3) a groundwater monitoring well located on Pueblo de San Ildefonso land within Mortandad Canyon that was installed as part of the cleanup effort for the hexavalent chromium plume beneath Los Alamos National Laboratory.
On November 2025, NMED ordered DOE-EMLA immediately cease all injection operations associated with the plume due to analytical results showing that the sole source regional aquifer beneath the Pueblo exhibits hexavalent chromium concentrations exceeding the regulatory standards set forth in the New Mexico Administrative Code.
The injection operations were developed by DOE in 2015 as part of a corrective action remedy under the Chromium Plume Control Interim Measures (IM) DOE developed to treat the plume in groundwater and to mitigate off-site migration. NMED says the IM was approved by NMED based on the investigation data, modeling, and justifications that DOE presented. It consisted of extraction of groundwater, ex-situ treatment, and reinjection of the treated groundwater. The theory was, NMED says, that the reinjected groundwater would provide hydraulic control, preventing off-site migration of contamination. NMED agreed to implementation of the IM, pending monitoring data demonstrating the efficacy of the IM and the implementation of a final remedy.
The NMED’s November 18, 2025 letter stated that “actual monitoring data has shown the IM is not protective and is not mitigating off-site migration, as evidenced by data showing horizontal and vertical migration of contamination”
“Since at least 2021, NMED has communicated to DOE that the effects of the injection activities under DP1835 indicated increasing trends in hexavalent chromium in a downgradient monitoring well in the eastern portion of the plume. Additionally, in 2019, a monitoring well installed farther east in the plume showed hexavalent chromium concentrations deeper than expected, which was a discovery that did not align with the conceptual site model DOE used to justify the injection well locations. This 2019 monitoring data also did not align with the predictions from the groundwater modeling DOE performed to justify the IM injection approach. Due to these increasing horizontal and vertical
contaminant trends, on December 12, 2022, NMED issued an order to cease injections,” the letter states.
In February 2023, DOE submitted its Initial Five-Year Evaluation of the Interim Measures for Chromium Plume Control to NMED, reevaluating the groundwater modeling and stating that continued operation of the injection wells is critical to the extraction and treatment of contaminated groundwater. DOE insisted that operating the injection wells is the only scenario that reduces chromium concentrations to below the NMAC standard of 50 parts per billion (ppb). and that reverting to full IM operation would provide important new information on plume behavior that would aid in the design of the Final Remedy for the plume.\
In May 2024, NMED authorized partial operation of three underground injection control wells
while indicating that it was conditional, and that reevaluation of the temporary authorization would be necessary “if the ongoing hexavalent chromium concentrations in monitoring wells along the periphery of the current known plume extent, both upgradient and downgradient of injection operations, indicated concerning contaminant trends”.
In December 2024, an independent technical review team (ITR) to evaluate the technical differences regarding the hexavalent chromium plume IM said in its report:
(1) statements that the current IM system at full operations would not contain all chromium
migration and that the IM will likely need to be modified, reconfigured, and expanded;
(2) emphasis on the need to reanalyze the groundwater model to account for uncertainties specified in the report and support for the need to convert the current model to MODFLOW, a model with more widespread use;
(3) support for NMED’s determination that IM injection has adversely impacted chromium
concentrations in monitoring wells;
(4) support for NMED’s requirement to install an alternative injection location for treated water and encouraged a partial restart of IM operations conditional on the data collected in SIMR-3; and
(5) recommendations that the modifications to the treatment system should not wait until final remedy selection and that the IM should be modified using an adaptive management approach.
NMED said the recommendations in the report aligned with the proposals and regulatory directives NMED had urged all along, and that DOE had refused to implement.
After the report was issued, in July 2025, DOE began installing SIMR-3, located on the Pueblo to inform the boundary of contamination south of injection wells CrIN-3, CrIN-4 and CrIN-5 and following the zonal sampling of the groundwater from SIMR-3, analytical results from October 2025 confirmed chromium contamination is present within the sole source regional aquifer beneath the Pueblo at concentrations that exceed state regulatory standards.
The November 2025 letter to DOE says this data shows that the injections at treated CrIN-3, CrIN-4 and CrIN-5 have resulted in adverse migration of contamination, both offsite and downgradient of the reach of the current interim measures treatment system and that the IM has clearly failed to contain the plume.
“DOE has repeatedly stated that the remediation of the hexavalent chromium plume is the highest priority action for DOE, yet DOE has not made adequate progress towards regulatory compliance with the requirements to modify and expand the IM treatment system. DOE has not complied with the regulatory requirements and directives to expand and modify the IM pump-and-treat system to meet the goals of interim measures. DOE challenged NMED’s authority to require implementation of necessary actions under interim measures, disagreed with the technical reasoning for the need to modify the IM, and squandered critical time justifying a position that was not protective of human health and the environment, instead of solving the problem,” the letter states. “DOE’s disregard for regulatory directives has allowed the chromium plume to spread further into previously uncontaminated areas.”
“Since 2021, DOE has neither complied with NMED’s regulatory directives nor made substantial progress towards ensuring the protection of the regional aquifer. The latest sampling results from SIMR-3 prove that DOE’s refusal to take appropriate steps to ensure that contamination does not migrate further in the regional aquifer or offsite has created the harm to the environment that NMED sought to prevent. DOE’s actions, as well as its inactions, in ignoring NMED’s years-long insistence that DOE comply with regulations, look at the alarming contaminant trends, and take actions to reduce and reverse the contaminant trends, show that DOE apparently does not value preservation of the sole source regional aquifer, and instead prioritizes cost and effort minimization to the detriment of the environment and human health,” the letter states.
On February 11, 2026 NMED announced filed legal action against DOE, (https://losalamosreporter.com/2026/02/11/environment-department-acts-to-hold-department-of-energy-accountable-for-failure-to-prioritize-cleanup-of-lanl-legacy-waste-for-disposal-at-wipp/) including an administrative compliance order and civil penalty of $6,026,124 related to hazardous waste violations and the 2024 consent order regarding LANL’s management of the chromium plume that migrated off-site and onto the Pueblo. DOE must submit a revised interim measures plan with an implementation schedule to NMED for approval. A copy of this enforcement action is available here. DOE has 60 days to submit an initial plan to further characterize and remediate the contamination that has migrated beyond the LANL boundary onto Pueblo land and implement a schedule that provides completion dates for each corrective action activity.
The compliance order notes that SIMR-3 has the potential to be used as an extraction well if necessary in the future. NMED is requesting that the plan include in detail the data and threshold points that will inform the need to begin remediation on the Pueblo.
The order requires DOE to begin extracting a minimum of 170,000 gallons a day of chromium contaminated groundwater from at least two extraction wells beginning May 10, 2026 and continue at least this rate of extraction until Oct. 31, 2026. When an alternative location is ready for operation, that volume of extraction is to be increased to 430,000 gallons a day year-round, which is equivalent to five extraction wells operating at 60 gallons a minute.
By Nov. 6, 2026, DOE has to submit a revised Interim Measure and Characterization Work Plan that will include implementation of the recommendations from the independent technical review team’s report. DOE also has to come up with a proposal for a high-capacity alternative location for the disposition of treated water, which at a minimum will be capable of disposing of water from all five current extraction wells, as well as an alternative to injecting into the existing injection network that must be located outside the plume extent both laterally and vertically.
The online agenda package for the BPU March 4 meeting does not yet have the NMED presentation document included. https://losalamos.legistar.com/View.ashx?M=PA&ID=1373720&GUID=9AE69F94-B356-42FE-851E-BCC78B3676FA
A – LANL Chromium Plume Presentation (will be shared when available)
Public Participation ~ in person or https://us06web.zoom.us/j/87563449773