Church Rock spill still shapes McKinley County cleanup efforts
Cleanup still centers on three Church Rock sites, where waste, radiation and groundwater work remain in the ground near Gallup.
The former United Nuclear Corporation mill about 17 miles northeast of Gallup sits on McKinley County’s cleanup map, alongside the Northeast Church Rock Mine in the Pinedale Chapter and the Old Church Rock Mine along State Highway 566.
On July 16, 1979, a tailings dam failed at the United Nuclear mill near Church Rock. EPA monitoring summaries put the spill at about 100 million gallons of tailings solution and 1,100 tons of tailings solids into the Rio Puerco, and EPA and NRC historical assessments call it the largest single release of liquid radioactive waste in the United States. EPA’s 1979 fact sheet puts the Church Rock Mill’s start at May 1977, and monitoring after the spill stretched roughly 115 miles downstream.
The former UNC Mill Site covers about 25 acres of processing area and 100 acres of tailings disposal area. About 3.5 million tons of tailings were disposed there before reclamation and groundwater corrective work continued. Active uranium recovery ended in 1982, surface reclamation is complete except for the south tailings cell area covered by two evaporation ponds, and an NRC-EPA memorandum of understanding for the site was executed in August 1988. The site has been under NRC license since 1977.
The Northeast Church Rock Mine is a former uranium mine at the northern end of State Highway 566, about 17 miles northeast of Gallup in the Pinedale Chapter of the Navajo Nation. EPA calls it one of the largest mines on the Navajo Nation and the highest-priority cleanup site. Under a 2025 consent decree, about one million cubic yards of contaminated waste will be removed from the site and transferred to the UNC Mill Site, with EPA putting the cleanup cost at nearly $63 million and the schedule at more than a decade.
The Old Church Rock Mine remains a 75-acre fenced area northeast of Gallup in the Church Rock Chapter, about 13 miles from town along the west side of State Highway 566. EPA investigations found elevated gamma rates and waste inside and outside the fence, and the agency announced a time-critical removal action agreement for the site in 2026. The Navajo Nation has 523 abandoned uranium mines, with funds available to begin assessment and cleanup at 230 of them.
Navajo Nation President Buu Nygren warned, “We cannot allow another 1979 Church Rock uranium mill spill.”
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