Background

Title I of the Uranium Mill Tailings Radiation Control Act (Act) required the cleanup of 22 inactive uranium-ore processing sites and vicinity properties. While the U.S. Department of Energy's (DOE) authority for surface cleanup expired in September 1998, there is no end date for the remaining groundwater remediation. Four of the original uranium processing sites (Mexican Hat, Utah; Monument Valley, Arizona; Shiprock, New Mexico; Tuba City, Arizona) are located within the Navajo Nation.

In 1983, DOE and the Navajo Nation entered into a cooperative agreement to facilitate the surface remedial action of the four sites. Funds provided by DOE to the Navajo Nation for cooperation under the agreement were directed to the Navajo Nation's Division of Natural Resources. The National Environmental Policy Act compliance documentation, which includes the Environmental Assessments as well as the Remedial Action Plans, was developed with the participation of the Navajo Nation.

The characterization of surface and subsurface radiological contamination involved a phased approach that included an aerial assessment, a mobile scan, and on-site sampling to delineate the extent of contamination according to specific removal criteria set by the U.S. Environmental Protection Agency (EPA). More than $100 million was spent on the surface remediation of the four processing sites and on the construction of three disposal cells. That agreement expired in 1998 along with the surface cleanup authority, and a new cooperative agreement was initiated for groundwater cleanup that remains in place.

Groundwater Cleanup at Milling Sites on the Navajo Nation

DOE-funded groundwater remediation and long-term surveillance and maintenance at the four Navajo Nation sites was $3.4 million in 2007 and estimated to be $3.2 million in 2008. The groundwater compliance strategies are reviewed annually with the Navajo Nation to track progress toward cleanup standards in the groundwater plumes. Based on our knowledge of the sites, DOE does not believe that additional funding would significantly accelerate the groundwater cleanup at the three processing sites where active remediation is in progress. DOE will continue to work with the Navajo Nation using the currently approved plans to complete groundwater remediation responsibilities.

Groundwater Cleanup at the Tuba City, Arizona, Site

At the former milling site near Tuba City, the Office of Legacy Management (LM) removed 259 million gallons of contaminated water from the aquifer and extracted 558 pounds of uranium, 867,000 pounds of nitrate, and 2,146,000 pounds of sulfate. After distillation under vacuum at 145 degrees Fahrenheit, 227 million gallons, or 88 percent of the extracted water has been returned to the aquifer to aid in flushing contaminants. The cleanup goals for this site are 44 micrograms uranium per liter and 250 milligrams sulfate per liter.

To improve energy efficiency at the Tuba City plant, solar heating is being installed to preheat the incoming contaminated water through a heat exchange with the clean water. This plant improvement is projected to save approximately 210,000 kilowatt hours per year and about $16,000 per year in electrical power expenses. Given a rather high escalation for electrical power costs in the area, the expected break-even point is in 11 years, while the plant will operate for at least 20 years.

Interagency Effort to Address Environmental Impacts to the Navajo Nation

LM staff participated in an interagency workgroup meeting in December to discuss uranium contamination of two sites near Tuba City. The sites are the Highway 160 Site and the Tuba City landfill. These sites were not identified by DOE for clean up during the surface remedial action program. LM is working with the Bureau of Indian Affairs (BIA), the U.S. Geological Survey, and the EPA to develop sampling and treatment options at the landfill site. This effort addresses some of the concerns expressed by the House Committee on Oversight and Government Reform led by Congressman Henry Waxman. The BIA and EPA are exploring funding for the effort. Activity by LM is limited unless cleanup authorization under the Uranium Mill Tailings Radiation Control Act can be renewed. LM will lead a technical information exchange meeting in February to better define agency roles and to understand the concerns of the Navajo Nation.