The Lukachukai Mountains Mining District is a Superfund site on the Navajo Nation in northeastern Arizona, covering roughly one hundred waste piles from uranium and vanadium mines that operated between 1949 and 1968. The U.S. Environmental Protection Agency (EPA) added the site to the National Priorities List (NPL) on March 7, 2024. More than 800,000 cubic yards of mine waste remains across the district from both surface and underground operations.
The main contaminants are radium-226, uranium, and heavy metals left behind in mine waste from the Morrison Formation. These materials have migrated downstream through washes and may have reached groundwater and surface water. Past ore hauling spread contamination along miles of mountain roads. Current assessments confirm that human exposure is not under control and that an unsafe level of contamination has been detected. Groundwater migration status is uncertain because there is not yet enough data to determine whether contaminated groundwater movement has stabilized.
The site is divided into five operable units (OUs). These are the Fund Lead Mines source control, the Tronox Mines source control, the Cyprus Amax Mines source control, sitewide groundwater and surface water, and one sitewide unit. The remedial investigation (RI) for the Fund Lead Mines OU began in August 2023. Investigation of sitewide groundwater and surface water is scheduled to start in April 2025. Studies for the Tronox and Cyprus Amax mine areas are estimated to begin between January and July 2027. No cleanup remedy has been selected yet, and construction of remedial actions has not started. Decision documents have not been issued for most operable units.
Institutional controls are already in place to limit exposure. These include zoning restrictions that block residential development and other uses inconsistent with current cleanup levels. Many Navajo families live on the mountain. The land is used for livestock grazing, recreation, hunting, and gathering medicinal plants for traditional ceremonial purposes. The area also provides habitat for the federally threatened Mexican spotted owl and other sensitive species.
Community members can get involved by contacting the EPA's Community Involvement Coordinator, who handles public engagement questions, or the Remedial Project Manager overseeing the technical investigation.
