State and DOE outline continued work to locate and contain chromium plume from LANL

Mike Peterson, a hydrogeologist with the New Mexico Environment Department (NMED), told the Los Alamos Board of Public Utilities on April 16 that the agency and the Department of Energy are continuing interim measures to limit movement of a chromium plume that originated from operations at Los Alamos National Laboratory (LANL).

Peterson said extraction wells in the plume centroid (CREX 2, CREX 4 and CREX 5) were restarted and treated water is being reinjected into southern wells (KRYN 3, 4 and 5) to hold the plume while more data are collected. “My name is Mike Peterson. I'm a hydrogeologist, with the Hazardous Waste Bureau,” he said during the presentation.

The update included three near‑term priorities: operate the interim pump‑and‑treat system in a way that minimizes unintended deepening or lateral migration of chromium; drill a set of data‑gap monitoring wells (including one on Pueblo lands) to better define lateral and vertical extent; and move the site’s environmental compliance paperwork forward after an independent technical review (IRT) identified areas needing improved design and monitoring.

Why it matters: NMED and DOE said the interim system has removed only a small portion of the original contamination; Peterson said roughly 60,000 pounds of potassium dichromate were released decades ago and the interim measures have removed about 2,000 pounds (roughly 1 percent). The plume’s depth and distribution are uncertain in places, and the proximity to Pueblo de San Ildefonso land and municipal water resources makes containment and accurate characterization a priority.

Details of the interim program and monitoring plan

Peterson described the source as operations at a TA‑3 power plant where potassium dichromate was used for corrosion control in the 1950s–1970s. Early monitoring and modeling assumed most contamination was in the upper ~50 feet of the regional aquifer; more recent sampling shows chromium present deeper in places. Peterson said, “we're really starting to discover that things are starting to move a little bit deeper than originally hoped for.”

The interim measures were partially restarted on Sept. 30, 2024; not all five extraction wells were turned on. NMED and DOE requested an Independent Technical Review after an impasse over whether injections had caused unexpected spikes at monitoring well R‑45. The IRT recommended resuming selected extraction wells while adding monitoring and alternative injection options.

Peterson listed high‑priority new monitoring wells as SIMR‑3 (on Pueblo lands to assess contamination there), R‑709 (across from the shooting range), and R‑80 (to evaluate trends down‑gradient of R‑45). He also said R‑73 needs to be redrilled and R‑77 should be deepened to sample the deeper Chumeta formation, which supplies many of the municipal wells.

State role and dispute resolution changes

Peterson said the updated Compliance Order on Consent (finalized Sept. 24) formalizes a faster, expert‑mediated path to resolve technical disputes between NMED and DOE. Under the revised process, the agencies will first attempt technical and managerial reconciliation; if unresolved, they will jointly select an expert or panel whose findings are binding on the parties. Peterson described the IRT process as a proof of concept and said both parties shared data, maps and access with the experts.

Questions from the board and technical clarifications

Board members asked how long new monitoring wells take and how much they cost. Peterson said a typical monitoring well takes about three to six months from bid to completion (one recent well took about a year because of complications) and said DOE has estimated $5–8 million per well for some of the monitoring or replacement wells being considered.

Caitlin Martinez of NMED's Hazardous Waste Bureau emphasized the interim nature of the pump‑and‑treat system and the goal of preserving plume boundaries while the agencies obtain the data needed for a final remedy. “This is kind of the whole point of the interim measures…this is a temporary solution,” Martinez said.

Board and local concerns

Board members and county staff raised the technical and water‑resource implications of using existing wells (such as PM‑3) for injection. County officials said converting PM‑3 to an injection well would require a replacement municipal production well to preserve water supply; the county also has applied for funds to study replacement well options. NMED staff said alternatives—including deep injection wells, reuse as surface water, spreading basins or vadose‑zone injection—are being evaluated and that return‑flow and water‑rights implications must be considered.

Outlook and next steps

Peterson said the state expects at least five years of additional work before the state would consider selecting a final remedy, and cautioned that additional monitoring wells may be required if those wells do not sufficiently define the plume’s nature and extent. He said approximately 2,000 pounds of chromium have been removed to date from an estimated 60,000 pounds released down the canyon historically.

The Board of Public Utilities did not take an action on the presentation; staff said they will receive periodic updates as monitoring and interim activities continue.

Ending

NMED and DOE officials asked the board and county to stay engaged as technical evaluations continue and new data arrive. Peterson closed by warning that more updates will be needed over several years to resolve the plume’s extent and to develop a final remedy.