Lawmakers Raise Alarm Over Los Alamos Chromium Plume
New Mexico legislators say a hexavalent chromium plume from Los Alamos National Laboratory is spreading beneath Pueblo de San Ildefonso land.
Updated on Nov. 9, 2026 in Nuclear
Live Poll
Do you trust local government to protect your community from pollution?
New Mexico legislators raised alarm at a committee hearing over a hexavalent chromium plume that has spread into underground aquifers beneath Pueblo de San Ildefonso land. The contamination traces to a non-nuclear powerplant at Los Alamos National Laboratory, where workers flushed contaminated water into Sandia Canyon from 1956 to 1972.
Why it matters
The plume raises questions about legacy contamination at a major federal research site and its effects on neighboring tribal land and water. The lab has not yet signed a waste cleanup settlement with the New Mexico Environment Department, leaving the remediation timeline unsettled.
The lab has shipped more than 90% of above-ground legacy waste, while contaminated water was flushed into Sandia Canyon from 1956 to 1972. The extent of the underground plume and the timing of a final cleanup agreement remain unresolved.
The players
Los Alamos National Laboratory
A federal research laboratory in New Mexico that has shipped off more than 90% of its above-ground legacy waste and is working to restart a groundwater interim measure.
New Mexico Environment Department
The New Mexico state agency responsible for environmental regulation, currently negotiating a waste cleanup agreement with the laboratory.
Pueblo de San Ildefonso
A Tewa Pueblo community in northern New Mexico whose underground aquifers have been affected by the chromium plume.
The details
Workers at the laboratory's non-nuclear powerplant flushed contaminated water into Sandia Canyon between 1956 and 1972, and the contamination later reached underground aquifers beneath Pueblo de San Ildefonso land. Lab representatives met with New Mexico Environment Department officials in August to negotiate a waste cleanup agreement, which has not yet been signed.
Timeline
1956 to 1972: Contaminated water is flushed into Sandia Canyon.
August: Lab representatives meet with the New Mexico Environment Department on a cleanup agreement.
November 5, 2026: Lawmakers raise plume concerns at a committee hearing.
Legacy Contamination
New Mexico has 261 abandoned mines, and the Navajo Nation maintains a moratorium and law prohibiting uranium mining near Mount Taylor, a backdrop against which the proposed Energy Fuels mine is being weighed. The chromium plume adds to a long record of federal and state environmental cleanup disputes in the state.
Residents of nearby Pueblo communities who rely on groundwater may face uncertainty about water safety until cleanup is finalized. The outcome of the pending settlement will determine how quickly contaminated aquifers are treated.
The takeaway
Legacy contamination from decades-old industrial practices can persist for generations, and final cleanup depends on enforceable agreements between federal facilities and state regulators. Readers tracking the issue should watch for the signed settlement and any updated plume data.
Further reading
For more on nuclear policy and waste cleanup in the state, see Nuclear.
Live Poll
Do you trust local government to protect your community from pollution?
