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NMED says new monitoring well shows chromium above state action level; proposes adaptive site-management steps
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Summary
NMED told the Los Alamos Board of Public Utilities that screening samples from a new monitoring well show chromium concentrations above the state's 50 ppb action level in lower zones; the department proposed using RCRA/ITRC adaptive site-management frameworks, paused reinjection, and pursuing extraction-and-treatment pathways while refining modeling and monitoring.
New Mexico Environment Department officials updated the Los Alamos Board of Public Utilities on March 4 about screening results from a newly installed monitoring well and outlined an adaptive site-management approach to guide next steps in addressing the chromium plume from LANL.
Mike Peterson, a water-resource professional with NMED's Hazardous Waste Bureau, said screening-level sampling from SIMR3 — a well drilled on Pueblo de San Ildefonso property — identified the highest chromium concentrations in the lower zones and that some injection wells have yielded concentrations “ranged from 60 to a 100 parts per billion,” above the state's action level of 50 parts per billion. Peterson said the zonal-sampling data drove a dual-screen design for the well and that the well’s final cement seal had been emplaced and production and aquifer testing would begin shortly.
Caitlin Martinez of NMED's Groundwater Quality Bureau described adaptive site management as a structured, iterative decision process that brings stakeholders together to set objectives, collect targeted data and revise actions as new information arrives. Martinez said NMED is drawing on two guidance approaches — the RCRA FIRST (Facilities Investigation Remedy Selection Track) framework and ITRC remediation-management guidance — to build a corrective-action framework for LANL and to avoid recursive disputes over technical interpretation.
Martinez said the stakeholder group identified to date includes Los Alamos County, Pueblo de San Ildefonso, the Department of Indian Affairs, the Office of the State Engineer, NMED bureaus and DOE. She said NMED supports restarting extraction and treating contaminated groundwater where reinjection is not authorized; under one discussed pathway, a land-application discharge mechanism could allow treated-water disposal, with a cited permitted capacity in the discussed option on the order of 350,000 gallons per day. Martinez emphasized that NMED views these steps as iterative and that initial measures are not intended to be the final remedy.
Board members repeatedly pressed NMED on groundwater modeling and whether prior injection/extraction operations could be displacing the plume. NMED said DOE has submitted FEHM-model outputs the state has reviewed but that mutual technical acceptance is still being worked toward. Martinez acknowledged model uncertainty at multi-decade horizons and said NMED will rely on combined data, monitoring and technical review to guide modifications.
Peterson said SIMR3 will be added to the standard monthly sampling schedule and that the initial results are screening-level (nonregulatory) samples meant to inform well placement and monitoring. He and Martinez said routine county drinking-water testing has not detected elevated chromium in county production wells but that NMED prefers “a bias for action” to limit potential future risk to downgradient receptors.
Next steps: NMED said it intends to work with stakeholders on a modified interim-measures work plan that incorporates independent technical-review recommendations and the adaptive management framework; staff expected to return to the board with progress in the coming year.
