LANL posts April groundwater review to public cleanup reading room

New documents were added to the Los Alamos Legacy Cleanup Contract Electronic Public Reading Room, including a Monthly Notification of Groundwater Data Reviewed in April 2026, giving residents another look at the laboratory’s long-running groundwater record. The posting lands in a public archive maintained by the U.S. Department of Energy’s Environmental Management Los Alamos Field Office and N3B Los Alamos, where cleanup documents required to be posted after April 30, 2018 are kept for public review.

For Los Alamos County, the significance is less about the paperwork itself than about what it shows: groundwater monitoring at Los Alamos National Laboratory is still being documented, reviewed and disclosed through a system built for environmental oversight. LANL’s Electronic Public Reading Room says it contains documents required for compliance with environmental regulations and permits, and the laboratory’s research library says recently added records can be found through a New Records in EPRR link. The new monthly groundwater notice fits that system, adding another technical checkpoint rather than a new public-relations milestone.

The context for that monitoring is the lab’s hexavalent chromium plume beneath Sandia and Mortandad canyons. DOE says the contamination came from releases between 1956 and 1972, when cooling-tower water containing potassium dichromate was flushed into Sandia Canyon. The plume was later discovered in 2004, and DOE says it has worked with the New Mexico Environment Department since then to install monitoring wells and operate a treatment system.

Publicly available DOE material says two sentinel wells between the plume and the nearest downgradient water-supply well are sampled monthly. It also says Los Alamos County water-supply wells are outside the plume, while the Buckman Well Field serving part of Santa Fe’s supply sits about five miles away and is considered an extremely unlikely pathway of concern. That is the part of the story local readers watch most closely: whether each new posting changes the basic picture of risk. So far, the April review appears to reinforce the same answer, that the contamination remains under active observation and the cleanup record is still being updated.

The broader disclosure network around the lab includes Intellus, which LANL describes as a public database of environmental surveillance and compliance records collected by the laboratory and the state. DOE also posted a public hexavalent chromium campaign update on April 7, 2026, showing the issue remains under active review with NMED, the New Mexico Office of the State Engineer, Pueblo de San Ildefonso and Los Alamos County. For nearby residents, the latest reading room entry is another sign that the groundwater file is still open, still expanding and still central to how the community measures cleanup progress.