The US NRC has assessed that shifting the waste from a mine site in New Mexico to a neighbouring mine site would be beneficial for a community that would rather see the waste removed out of state. The site is just one of hundreds affecting members of the Navaho Nation.

Northeast Church Rock (NECR) is a former uranium mine in McKinley County, New Mexico, USA, that was operated by United Nuclear Corporation (UNC) between 1967 and 1982. UNC also operated the Church Rock uranium milling facility, less than 1.6km distant, from 1977 to 1982 under a licence issued by the State of New Mexico.

Uranium from the NECR Mine Site and other local mines was processed at the mill facility, and residual materials (‘tailings’) were placed in an impoundment (also known as a tailings dam).

Work at these two sites directly affects the local populations. Three small communities – Red Water Pond Road, Pipeline Road and Pinedale – are all within a kilometre or two of the sites or between them.

The sites are just two of hundreds in the region, but they illustrate the complexities of responding to the environmental degradation incurred in sourcing the fuel needed for the nuclear industry of the last century. Most significantly, the UNC Mill Site – and the surrounding country – suffered the USA’s biggest ever radiological event, on 16 July 1979, when a failure of the tailings dam released 350 million litres (93 million gallons) of tailings into local river drainages and into the underlying alluvium. At NECR Following the tailings spill and related corrective actions, UNC resumed uranium milling operations, and eventually, some 3.2Mt of tailings were held in the tailings impoundment at the UNC Mill Site.

The US NRC now proposes to go ahead with a $42 million project to shift contaminated material from the mine to long-term storage at the milling facility. It says the project will release land to local people and reduce the possibility of contamination spread, and it proposes to go ahead even though many local Navaho tribespeople say that rather than shifting waste a short distance – with around four years of truck movements and other local disruption – they want to see the waste removed from the region entirely.

An unwanted legacy

There are 524 known abandoned uranium mine sites that were built and worked between 1944 and 1986 on the land that constitutes the Navajo Nation, in areas that often have social and religious significance for people that live in the region. According to the United States Environmental Protection Agency, over 30Mt of uranium was extracted from the mining sites on Navajo lands during that time. The Navajo Environmental Protection Agency (EPA) believes there could be far more.

In a meeting in September 2022 between Navajo Nation President Jonathan Nez and Council Delegate Rickie Nez, US Environmental Protection Agency (EPA) and Administrator Michael S. Regan and Deputy Administrator Janet McCabe, the Navaho representatives asked for faster work on remediation. They said that only 219 of the mine sites have available funds for clean-up and remediation efforts, leaving a total of 305 unaddressed.

Council Delegate Nez, who serves as the chair of the Resources and Development Committee, called on the federal EPA to clean up uranium sites in the Navajo Nation as quickly as possible. “By working together with the Biden-Harris Administration over the last couple of years, we have built a lot of momentum on many issues including the cleanup of uranium waste. Progress is in the works and we will begin to see more mines addressed in our communities” said President Nez.

Administrator Regan said that the federal EPA is creating field offices located in the capital of the Navajo Nation and Flagstaff, Arizona, dedicated to working with the Navajo Nation EPA. The EPA also reported that it is working with the US Department of Energy and the Navajo Nation to conduct assessments and are prioritising more than 300 uranium mine sites that do not yet have funding for remediation.

According to a press release issued following the meeting, Administrator Regan visited an abandoned uranium mine close to occupied homes the previous year, while in April, USNRC representatives visited the Redwater Pond Road Community, to hear from local Navajo residents about the “devastating impacts caused by uranium mining”.

Two sites in the spotlight

The two sites in McKinley County are among those that are on the agenda for remediation. But deciding on the next steps for the two sites has been a long process.

UNC Mill Site: In 1986 the NRC reassumed regulatory authority for the UNC Mill Site and it approved a reclamation plan in 1991, after several iterations. Now surface decommissioning and reclamation of the former mill facilities and three tailings cells (South, Central, and North) and two borrow pits is complete, except for the area on the South Cell covered by two evaporation ponds. An NRC-approved groundwater corrective action plan includes a pump-and-treat groundwater extraction system and evaporation ponds for the disposal of treated water. The remaining final site reclamation activities include placing a final radon barrier and erosion protection, with other groundwater corrective actions.

NECR Mine Site: While the NECR Mine Site mine operated, it was the principal mineral source for the UNC mill. Its 83.8Ha area is mostly on Navajo Nation land or Navajo Nation Trust land and private land. The NECR Mine Site consists of two shafts, two uranium ore waste piles, several mine vent holes, and a production well 550m deep that was used to dewater the mine workings during operations. After the mine was shut down, residual materials, including low-grade uranium ore, waste rock, and overburden wastes, remained at the site. UNC undertook various closure activities between 1986 and 1994, including backfilling and sealing the two mine shafts and associated vent holes and regrading, covering, and revegetation of materials storage areas.

Because tailings material from the UNC Mill Site had been previously authorised by the State of New Mexico for backfilling mine workings at the NECR Mine Site, residual tailings materials remained in stockpile areas at the mine site that also required remediation. After the NRC assumed licensing authority over the UNC mill tailings, the residual tailings at the NECR Mine Site were removed and transferred back to the UNC Mill Site tailings impoundment, and related facilities at the mine site were decommissioned in accordance with the NRC licence.

Next steps

The EPA has determined that the mine waste presents a threat to public health and now the NRC has published an Environmental Impact Assessment (EIA) – a significant step in the process of cleaning up the sites – a process that has already lasted much longer than either site was in active use. It says it is necessary to remove the NECR mine waste to allow for remediation of the NECR Mine Site and productive uses of the land, such as grazing and farming, and cultivating traditional plants for dyes and medicinal uses. The EIA says that the ‘no-action’ option would mean restricted land use “would continue to noticeably influence the ability of the Navajo Nation to use the land”. The NRC staff concluded that under the no-action alternative, there would be a ‘large’ impact on land use as a result of uranium mining.

Different parts of the two sites to be addressed are licensed by different agencies – the US Nuclear Regulatory Commission (USNRC) licenses the tailings impoundment at the UNC Mill Site, for example, but does not license other parts of the site.
Interim EPA cleanup has seen over 200,000 tonnes of contaminated material removed from residential areas to address immediate exposure concerns. In 2005, following a request by the Navajo Nation Environmental Protection Agency (NNEPA), the EPA agreed to assume jurisdiction for the mine cleanup and act as the lead regulatory agency for the NECR Mine Site.

In the next step, UNC wants to transfer around 765,000 m3 of waste from the NECR mine to be stored above the tailings impoundment at the UNC Mill Site.

Principal threat waste (PTW) would not be moved. PTW is defined by EPA as source materials that are considered to be either highly toxic or highly mobile. EPA has defined PTW at the site as material that contains 7.40 Bq/g or more of Ra-226, and/or 500 (mg/kg) [500 ppm] or more of total uranium. That material cannot be sent to the disposal site above the UNC tailings impoundment. Instead, UNC’s proposal is to transport the PTW to the White Mesa uranium mill in Blanding, Utah, but UNC is not expected to finalise arrangements for disposal until the current works are completed.

The proposal

The UNC Tailings Impoundment is an engineered and covered impoundment located on the UNC Mill designed and constructed to address NRC criteria to isolate tailings from the environment, control radiological hazards, and limit radon releases for up to 1,000 years. Eventually, the NRC expects the tailings impoundment would be transferred to a government custodial agency for long-term surveillance.

The mine waste has radiological characteristics comparable to the tailings at the UNC Mill Site because both are derived from the same uranium ore material. NECR mine waste that exceeds a Ra-226 concentration of 200 pCi/g would not be sent to the UNC Mill Site because it is considered PTW.

UNC proposes to transfer the NECR mine waste to the proposed disposal site using articulated dump trucks on access and haul roads that connect the two sites. One alternative would use an elevated conveyor system to transfer most of the waste at an additional cost of $1 million. In this case, about 5% of NECR mine waste would still have to be transferred by truck (which would have a slightly higher impact than in the main proposal because it could not use specially constructed haul and access roads). But most of the NECR mine waste would avoid crossing New Mexico Highway 566 at ground level, which would reduce the potential transportation-related impacts. UNC estimates that this alternative would disturb 0.8Ha less than the proposed haul and access roads although construction of the conveyor and a bridge over the highway would involve shipments and temporary lane closures and interruptions to transportation.

Another alternative would source cover material from other areas. This would reduce costs by $3 million, the assessment says.

UNC proposes to install permanent stormwater controls for the proposed disposal site using existing swales and channels constructed on the tailings impoundment, with improvements and supplemental controls where necessary.

The proposed project phases would last around four years, including the construction and transfer of NECR mine waste, and the closure of the constructed disposal site. Another 10 years may be needed for other activities, including the completion of UNC Mill Site reclamation, groundwater corrective action and NECR Mine Site.

The long-term (post-closure) timeframe includes long-term isolation of tailings and wastes and the effects of land use restrictions and requires that a mill tailings disposal facility be designed to provide “reasonable assurance of control of radiological hazards to… be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years”.

In the EIA the NRC recognised that “the Navajo Nation government and members of local Navajo communities oppose the proposed action – the transfer and disposal of mine waste onto the existing UNC Mill Site – and prefer that the waste be moved far away from the Navajo Nation”. It also recognised that “Navajo Nation communities are closer than any other community to the proposed project area and would be disproportionately affected by transportation-related impacts, impacts to air quality, increased noise levels, and visual disturbances”. Mitigation included EPA programmes to provide community members with voluntary alternative housing and mitigations proposed by UNC during the action.

But, overall, the NRC concluded that the programme would be beneficial. Removal of mine wastes from the former NECR Mine Site and consolidation of the mine materials over existing mill tailings on private property would minimise the footprint of waste disposal facilities and allow beneficial reuse of the NECR Mine Site.

This article first appeared in Nuclear Engineering International magazine.