Chromium Plume

Ensure contamination doesn’t threaten human and environmental health

Chromium Plume History

From 1956 to 1972, chromium-contaminated water from cooling towers was periodically released from the cooling towers into Sandia Canyon. Chromium was commonly used as a corrosion inhibitor. The water flowed from the power plant down Sandia Canyon as surface water, penetrated the underlying rock layers, and in time seeped into the regional aquifer beneath Sandia and Mortandad canyons. LANL ceased releasing chromium-contaminated water in 1972.

contaminant of concern:

Hexavalent Chromium


Conduct Interim Measure to prevent migration of plume beyond LANL boundary, obtain data necessary to conduct Corrective Measures Evaluation (CME), and conduct CME

Chromium Interim Measure at a Glance

Interim Measures are used to reduce or prevent migration of site-related contaminants which, have or may result in an unacceptable human or environmental receptor risk while long-term corrective action remedies are evaluated and implemented. In the case of the hexavalent chromium plume, the chromium interim measures combine extraction of contaminated groundwater, above-ground treatment, and injection of treated water to control plume migration, reduce the size of the plume and hold it within the LANL boundary.

Why it’s needed

The chromium interim measures approved by NMED are being conducted to mitigate plume growth and reduce the size of the plume.

How it works

Contaminated water is extracted and treated using ion-exchange technology. The treated water is then injected along the plume edge. Chromium concentrations will be reduced at the plume edge and the plume footprint will be reduced in size.

What’s Next

Technical data and analysis shows the chromium interim measures have been successful in controlling plume migration. Long-term corrective action remedies are being evaluated while additional wells are in the planning and permitting process to further define the plume.

September 2023 Status

  • Interim measures turned off March 31, 2023, to comply with New Mexico Environment Department direction.
  • Evaluating final remediation strategies.

Final Remedy

The chromium interim measures have demonstrated success in controlling potential plume migration. The chromium IM methodology is expected to be integrated into the final remediation remedy, which will be determined by NMED and requires public input.

By the Numbers


parts per billion

New Mexico groundwater standard for chromium



Distance (as measured at the surface) of the plume from the Rio Grande



Number of monitoring, extraction and injection wells installed in and around the plume



Amount of chromium contamination in Los Alamos County drinking water wells



Depth of the regional aquifer. Chromium is located within the top 100 feet of the  aquifer.


mile long x 1/2 mile wide x 100 ft. thick > 50ppb

Approximate size of the Chromium plume



Approximate distance from the plume edge to the  nearest Los Alamos County groundwater well

Chromium Plume Map