The U.S. Department of Energy (DOE) Office of Legacy Management (LM) is committed to managing its responsibilities associated with the legacy of World War II and the Cold War. This legacy includes radioactive material, chemical waste, and hazardous environmental contamination at more than 100 sites across the country.

Four of these sites are located within Navajo Nation, which covers 26,000 square miles and holds large deposits of uranium ore. Two of the four former Uranium Mill Tailings Radiation Control Act (UMTRCA) sites are located in Arizona near Monument Valley and Tuba City. The other two former UMTRCA sites are in Shiprock, New Mexico and Mexican Hat, Utah.

Approximately 4 million tons of ore were processed on the Navajo Nation from the 1950s to the 1980s. Mill tailings, a sandy waste containing radioactive heavy metals and radium, are a byproduct of the former processing operations. The tailings have caused significant surface and groundwater contamination at the four sites.

In 1978, Congress passed UMTRCA that established programs to protect the public and the environment from the effects of uranium mill tailings. By 1994, all surface remediation including disposal of residual radioactive material and debris had been completed at the four Navajo Nation sites in compliance with U.S. Environmental Protection Agency cleanup standards and regulations. By 1999, subsurface remediation work began. DOE analyzed the sites and developed specific plans, known as remedial action plans, to target mill-related contaminants. 

LM works with the Navajo Abandoned Mine Lands Reclamation/ Uranium Mill Tailings Remedial Action Department staff through a cooperative agreement to conduct long-term surveillance and maintenance on the Navajo Nation. Together, LM and the Navajo Nation monitor more than 1,000 wells and other features of the four Navajo Nation sites to ensure environmental compliance, public health, and safety.

In 2007, Congress directed DOE and other federal agencies to work together in consultation with the Navajo Nation to address uranium issues on the Navajo Nation through a Five-Year Plan. After each five-year period, the agencies report their results and make adjustments to ensure they are addressing the most significant risks to human health and the environment.

LM is committed to working with tribal programs and communities to reduce health and environmental risks associated with former uranium mill processing sites.