Homestake seeks NRC approval of alternate groundwater limits at Grants
Contaminant levels have fallen since remediation began in 1977 but progress stalled in the early 2000s, the company's application says.
Key facts
- Application filed June 30, 2026, to replace the groundwater corrective action program and protection standards
- NRC approved a license amendment in December 2025 for an evapotranspiration cover on the large tailings pile
- Tailings piles hold more than 22 million tons; the large pile covers about 200 acres
- NMED petitioned the NRC in October 2025 over the groundwater standards; the agency placed it in abeyance
- EPA record of decision for the groundwater unit, OU1, expected in 2027
Homestake Mining is installing an evapotranspiration cover system on the large tailings pile at its Grants Reclamation Project near Milan, New Mexico, under a license amendment the NRC approved in December 2025.
The cover replaces the upper 6-inch rock layer of the 1995 clay-and-rock-armor barrier design with a 12-inch vegetated surface layer of soil amended with 40 percent gravel. The design stacks the existing 12-inch interim cover, a 4.5-foot-thick lower radon barrier, a 3-foot-thick upper radon barrier and a 12-inch erosion protection layer. According to Homestake Mining, evapotranspiration covers are the current state of practice for closing mine waste sites in semiarid and arid regions; the soil and vegetation release water through evaporation and plant uptake rather than infiltration into the tailings.
Company seeks alternate concentration limits
Homestake Mining submitted a second license amendment request on June 30, 2026, seeking alternate concentration limits for groundwater at the site. The company proposes to replace its groundwater corrective action program and its approved groundwater protection standards with ACLs. Contaminant concentrations have fallen since groundwater remediation began in 1977, but progress has stagnated since the early 2000s, the company said, attributing the slowdown in part to back diffusion, in which contaminants bound in fine-grained clay layers are slowly released into adjacent sand and gravel. "Further groundwater restoration, including to background or current license groundwater protection standards, is not technically feasible," Homestake Mining stated in the application. The NRC declined to accept a separate ACL application in 2022 for detailed technical review. The New Mexico Environment Department petitioned the NRC in October 2025 to reevaluate the site-specific groundwater protection standards; the NRC placed the petition in abeyance pending review of the 2026 application.
EPA reviewing two operable units
The EPA is completing a CERCLA remedial investigation and feasibility study equivalency analysis for operable units 1 and 2, covering groundwater restoration and long-term tailings stabilization. The RI was completed in 2020, the same year Homestake Mining signed a settlement agreement with the EPA to perform the FS. The EPA said in March that the FS's second phase should be completed in 2026, and that a record of decision for OU1 is expected in 2027. The EPA issued a no-action record of decision for OU3, on radon in neighboring subdivisions, in 1989.
The mill operated from 1958 to 1990, and its buildings were demolished by 1995. The site was placed on the EPA's National Priorities List in 1983, and a 1993 memorandum of agreement with EPA Region 6 made the NRC lead regulator. After remediation and license termination, the project is to be transferred to the Department of Energy's Office of Legacy Management.
