Grants Reclamation Project: One remediation, multiple regulators

Under a license issued by the Atomic Energy Commission, the mill was initially operated by Homestake-Sapin Partners and Homestake-New Mexico. After several name and partnership changes in the 1960s, the site came under the ownership of Homestake Mining Company of California in 1981 and became known as the Grants Reclamation Project after decommissioning of the mill in the 1990s. In 2001, Homestake Mining became a subsidiary of Barrick Gold Corporation.

At its peak, the Homestake mill reportedly processed 3,400 tons of ore per day using an alkaline leach-caustic precipitation process. ³ Tailings generated from the milling operation were placed on two piles, a large tailings pile that is approximately 85-100 feet high and covering an area of about 200 acres, and a small tailings pile that is approximately 40 acres and 20-25 feet high. Combined, the piles contain more than 22 million tons of mill tailings.

While the Homestake mill was built to the industry standards of its time under AEC oversight, it was prior to the passage of today's environmental and industrial regulations, and the mill's tailing impoundments were left unlined. This resulted in groundwater contamination to the alluvial aquifer system below the site, which averages approximately 100 feet deep, as well as the underlying Chinle aquifer.

According to the Environmental Protection Agency, groundwater contaminants include both radioactive and nonradioactive constituents, including uranium, thorium-230, radium-226, radium-228, selenium, vanadium, molybdenum, sulfate, chloride, nitrate, and total dissolved solids. Ra-226 was the primary soil contaminant of concern, while airborne contaminants include radon-222.

Milling at the Grants Reclamation Project ended in 1990 and the mill buildings were decommissioned and demolished by 1995. Currently, in accordance with a groundwater remediation corrective action plan approved by the Nuclear Regulatory Commission, groundwater is being collected from on- and off-site wells and treated. The plan calls for restoring the groundwater aquifers to background concentrations.⁴

Overseen by the NRC with EPA input, the groundwater remediation system consists of a groundwater collection and injection system, an up-to-1,200-gallons-per-minute reverse osmosis water treatment facility, two lined collection ponds, three lined evaporation ponds, a groundwater collection and injection system for areas outside the facility's licensed boundary, and associated equipment and structures.²

Overlapping regulatory authority

What makes the Grants Reclamation Project particularly unique is the dual federal regulatory framework overseeing the remediation work. The site is a Superfund site under the EPA's Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) authority, having been placed on the EPA's National Priorities List in 1983. It is also licensed by the NRC, which is undertaking closure of the site pursuant to the Uranium Mill Tailings Radiation Control Act (UMTRCA).

The reason for the overlapping regulation has much to do with the site's long history and New Mexico's status as an NRC agreement state.⁵ After first being issued a source materials license by the AEC in 1957, New Mexico became responsible for licensing and regulating uranium milling operations at the site after becoming an agreement state in 1974. New Mexico eventually ended its agreement state status in 1986 and relinquished control of the site back to the NRC. By that time, however, the site had already been designated an EPA Superfund site.

To establish agreed roles and responsibilities for remediating the site, the NRC signed a memorandum of agreement with EPA Region 6 in 1993.⁶ Under the agreement, the NRC assumed the role of lead regulatory agency for the mill site and its closure activities, while the EPA agreed to monitor the work and provide comments directly to the NRC for review.

Speaking at the 2026 Waste Management Conference in Phoenix, Daniel Lattin, senior program manager at Barrick Gold, said the overlapping regulatory framework is "complicated to say the least."

Lattin said the issue with dual oversight was that it imposed two distinct and separate federal processes that at times had different procedural requirements. "It was a question of how to meet the individual agency requirements and not create a situation of [having] consecutive processes rather than concurrent processes," he said, adding that procedures done consecutively could create delays, while those done concurrently would be much more streamlined.

In addition to the federal regulators, the Grants Reclamation Project is regulated at the state level by the New Mexico Environment Department through a groundwater discharge permit.⁵ According to NMED, the NRC, the EPA, and New Mexico are all working cooperatively to complete site closure and continue remediation efforts to ensure protection of human health and the environment.

Finally, after the site is remediated and its NRC license terminated, the Grants Reclamation Project will be turned over to the Department of Energy's Office of Legacy Management for long-term maintenance and monitoring under the authority of UMTRCA Title II.

Equivalency analysis

The EPA has divided the Grants Reclamation Project into three operable units (OUs) to aid in completing site remediation. OU1 addresses groundwater restoration; OU2 addresses long-term tailings stabilization, surface reclamation, and site closure; and OU3 addresses radon concentrations in the site's neighboring subdivisions.²

The EPA has decided to take no action on OU3 after determining that the site was not a significant contributing factor to off-site radon concentrations, issuing a no action record of decision in 1989. The EPA is currently completing a CERCLA remedial investigation and feasibility study (RI/FS) equivalency analysis for OU1 and OU2, after which it will issue a record of decision for those units.⁷

The RI/FS equivalency analysis is to assess if the work completed at the site conforms with CERCLA requirements for investigation, risk assessment, and remedy selection. If it is determined that the work complies with the CERCLA requirements, it will demonstrate equivalency to a Superfund-quality remedy. If not, additional work will need to be completed before equivalency can be found.

The RI was completed in 2020, and that same year Homestake Mining signed a settlement agreement with the EPA to perform the FS. Homestake Mining's FS consists of two phases of activities. The initial phase is to develop a range of cleanup alternatives and then evaluate or screen the alternatives with respect to the following three evaluation criteria: effectiveness, implementation, and relative cost.

The second phase of the FS is to perform a detailed analysis of the retained alternatives to determine which best meets CERCLA criteria for a remedy. The EPA announced in March that this phase should be completed in 2026.⁷ A record of decision for OU1 is expected in 2027.

At the same time, Homestake Mining is conducting an evaluation to determine if it is technically impracticable to clean up the groundwater to drinking water quality. As part of the evaluation, the company is conducting a study to determine whether back diffusion is occurring at the site.

Back diffusion is a condition where contaminants that are bound up in fine-grained clay layers are slowly released back into adjacent coarser-grained layers of sand and gravel, where groundwater flows more easily. The condition can be affected by pumping operations designed to clean up the aquifers, and the continual slow release of the bound-up contaminants to the groundwater zones causes a rebound (increase) of contaminant levels in the flowing zones.

Homestake Mining is also evaluating whether the concentration of contaminants may be reduced through natural attenuation. Monitored natural attenuation of the site will be included as a component of the considered cleanup alternatives.

License amendments

Homestake Mining is currently installing an evapotranspiration cover system on top of the large tailings pile, having received NRC approval of a license amendment request (LAR) for the work in December 2025.⁸ The new cover system will update the current clay and rock armor-type barrier design, which was approved in 1995, by replacing the upper 6-inch layer of rock with a vegetated 12-inch-thick gravel-amended soil surface layer.⁹ (While Homestake Mining had installed radon barrier and erosion protection layers on the side slopes of the large tailings pile, it never completed the pile's top slope, which was covered by an interim cover layer.)

The new cover design will feature the existing 12-inch interim cover layer, overlapped by a 4.5-foot-thick lower radon barrier layer and 3-foot-thick upper radon barrier layer. The uppermost 12-inch erosion protection layer contains a mix of 60 percent soil amended with 40 percent gravel to mitigate erosion while providing a hospitable environment for vegetation.

According to Homestake Mining, evapotranspiration cover systems are the current state of practice for closure of mine waste sites in semiarid and arid regions.⁹ The cover is designed to provide long-term erosional stability, while limiting groundwater contamination by using the soil/gravel and vegetation so that water evaporates or is taken up by plants, rather than infiltrating through the cover into the tailings. At the same time, the updated radon barrier layers will further limit the release of radon.

Homestake Mining is also seeking to amend its NRC license to implement alternate concentration limits for groundwater at the site. The company is proposing to replace its groundwater corrective action program and currently approved groundwater protection standards with alternate concentration limits (ACL). The NRC is currently reviewing Homestake Mining's ACL LAR, which the company submitted on June 30, 2026.¹⁰

According to the company, while contaminant concentrations have significantly decreased since groundwater remediation began in 1977, progress to further reduce concentrations has stagnated since the early 2000s. Homestake Mining attributes the slowing progress in removing contaminants in part to back diffusion.³ "Further groundwater restoration, including to background or current license groundwater protection standards, is not technically feasible," the company stated in its LAR.

Homestake Mining had submitted a separate ACL LAR to the NRC in 2022, but the agency declined to accept the application for detailed technical review. In 2025, ahead of submitting the current ACL LAR, the company asked the NRC for a series of audits on the site's groundwater model, the as low as reasonably achievable (ALARA) demonstration, and the potential need for or use of institutional controls.¹¹ "The current application reflects additional data and analysis since the initial request," the NRC told Radwaste Solutions regarding the 2026 ACL LAR.

NMED petitioned the NRC in October 2025 to reevaluate and amend or change the site-specific groundwater protection standards for the Grants Reclamation Project, noting that opposition to the groundwater protection standards has been ongoing for nearly four decades by nearby residents and grassroots organizations.¹² The NRC, however, placed that petition in abeyance pending review of Homestake Mining's current ACL LAR.¹³

References

1. Wikipedia, Paddy Martinez, wikipedia.org/wiki/Paddy_Martinez
2. EPA, Superfund Site: Homestake Mining Co. Milan, NM, cumulis.epa.gov/supercpad/cursites/csitinfo .cfm?id=0600816
3. HMC, Technical Memorandum: Grants Reclamation Project Cessation of Corrective Action Program, NRC ADAMS ML22264A202 (May 27, 2022).
4. NRC, Homestake, nrc.gov/info-finder/decommissioning/uranium/homestake
5. NMED, Homestake Mill Site Review, env.nm.gov/
6. NRC, Notice of signing of memorandum of understanding, Federal Register (Jan. 26, 1994).
7. EPA, Homestake Mining Company Superfund Site Update (Mar. 2026).
8. NRC, News Release-25-067: NRC Approves License Amendment for Homestake Mining Company, NRC ADAMS ML26056A284 (Dec. 19, 2025).
9. Stantec Consulting Services, Design Report: Large Tailings Pile Evapotranspiration Cover Project, NRC ­ADAMS ML25163A319 (June 3, 2025).
10. NRC, Homestake Mining Company of California, Grants Reclamation Project, 2026 Application for Alternate Concentration Limits, NRC ADAMS ML26188A289 (June 30, 2026).
11. HMC, Request for NRC Pre-Application Audit Review, Homestake Mining Company of California-Grants Reclamation Project, NRC ADAMS ML26015A531 (Jan. 9, 2025).
12. NMED, New Mexico Environment Department 10 CFR § 2.206 Petition to the Nuclear Regulatory Commission Regarding the Homestake Mining Company Grants Reclamation Project near Grants, New Mexico (Oct. 24, 2025).
13. NRC, Placement of the NMED 2.206 Petition into Abeyance and Deferral of Issuance of an Initial Assessment (OEDO-25-00456), NRC ADAMS ML26156A229 (June 5, 2026).