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 Uranium Mill in Tuba City, Arizona


Tuba City Uranium MillTuba City Uranium Mill

The Tuba City Uranium Mill is a DOE facility (for remediation) from January 1985-February 1986 and January 1988-April 1990 so remediation workers are eligible to file both Part B and Part E claims.  Uranium Mill workers are covered under Radiation Exposure Compensation Act (RECA).  Workers who have been compensated under RECA 5 are eligible to file Part E EEOICPA claims.

The September 1982, History of Domestic Uranium Procurement under US AEC Contracts, Final Report, pages A-3 to A-6 extensively describes the work done at Tuba City Uranium Mill:

"Contract No. AT(05-13-293 was entered into with Rare Metals Corporation of America on July 15, 1955. It was replaced by Contract No. AT(05-1)-910, between the AEC and El Paso Natural Gas Company, which had acquired Rare Metals by a merger in July of 1962. The new contract was signed on November 19, 1962 and was effective from September 10, 1962 through December 31, 1966, with provision for final delivery of concentrate by February 2, 1967.

Through March 31, 1962, the AEC paid negotiated prices for the U3O3 m concentrates. Thereafter the price was the fixed $8.00 per pound of U3O8 established by the AEC's May 24, 1956 announcement.

Ore supplies for the Tuba City mill were obtained from the Cameron, Arizona, and adjacent areas and from the Orphan Lode mine owned by Western Equities, Inc., and located in the Grand Canyon National Park. That mine became the principal source of ore for the mill after rights to mine in the park area were resolved by Public Law 87-457, effective May 28, 1962.

On February 1, 1956, the AEC opened a uranium ore buying station at Tuba City millsite. The sampling plant, constructed and owned by Rare Metals, was leased to the AEC under Contract No. AT(05-l)-645, pending completion of the mill being erected at the same site. During the period FY 1956-1957, the AEC purchased 40,782 tons of ore averaging 0.22% U3O8 and 0.05% V2OS. This ore, as well as some ore from other AEC ore buying stations, or a total of 58,093 tons of ore, was
sold to Rare Metals, which processed it into concentrate for sale to the AEC. Ore acquired from the AEC was 8 percent of the total millfeed during the 11-year operation of the mill. Independent ore producers (including Western Equities, Inc.) supplied 78 percent of the ore processed in the mill, while contractor controlled mines furnished 14 percent.

The Tuba City mill ceased production shortly before Contract No. AT(05-1)-910 expired on December 31, 1966. The site is now inactive, and has been designated for remedial action under the Uranium Mill Tailings Radiation Control Act of 1978. A detailed description of the Tuba City site and tailings is contained in the report. Background Report for the Uranium Mill Tailings Sites Remedial Action Program, April 1981, (DOE/EP-OO11).

The Tuba City millsite is located in northern Arizona approximately 75 miles north of Flagstaff and 5 miles east of Tuba City on the Navajo Indian Reservation. The site is located along the south side of U.S. Highway 160, which connects Tuba City with Kayenta, Arizona, and is at an elevation of about 5,000 feet above sea level. The land around the site is rather desolate and is used by the Navajos for grazing sheep and cattle. The site covers 88 acres and consists of a mill, office and ore storage area (30 acres), a tailings area (22 acres), evaporation pond area (20 acres), and a housing area (16 acres) on both sides of the highway. The remainder of the site is all south of the highway. The site land was leased from the Navajo Nation and, shortly after the mill was shut down in 1966, full control of the site reverted to the Navajo Nation.

The mill began operation in June 1956 with a nominal capacity of 260 tons of ore per day; however, once start up difficulties were overcome, the capacity was stepped up to 300 tons per day, and the mill operated continuously at that rate until May 1962. At that time the mill was shut down pending negotiations with the AEC for a contract to continue operations. As noted earlier, the problem
concerning the right to mine ore that extended from the Orphan Lode mine under park land was resolved by PL 87-457. When the Orphan Lode mine became the principal ore supply for the mill it was necessary to modify the mill process. This was accomplished by installing used equipment acquired from the AEC m 1961 and 1962 by competitive bidding during the dismantling of the AEC's Monticello, Utah, mill. Once the new contract had been signed with the AEC, plant modification proceeded rapidly, and operations resumed in April 1963 at the design capacity of 200 tons per day. That daily throughput was maintained until plant shut down in late 1966. During the life of the Tuba City mill a total of 796,489 tons of ore averaging 0.33% U3O8 was processed and 90 percent of the U3O8 was recovered. All of the U3O8 produced was sold to the AEC.

The initial milling process consisted of crushing, grinding (in a pebble mill), sulfuric acid leaching, sand-slime separation, and recovery of uranium from the slime fraction by use of the basket resin-in-pulp ion exchange process. Most of the ores processed initially were of low lime content, less than 6% CaCOs, the exception being the Orphan Lode ore which ranged as high as 25% CaCOs. it was this high lime content that necessitated the process change when the Orphan Lode mine became the principal source of ore.

The mill conversion required the installation of additional ore grinding equipment, a flotation circuit to remove sulfides, which are carbonate consumers, pressure leach vessels (autoclaves), filters for liquid-solids separation, precipitation tanks, and solution carbonation equipment for leach solution recycle.

Equipment was also added to acid leach the sulfide flotation concentrate for uranium removal. The concentrate then contained sufficient sulfide copper to be marketable at a copper smelter. The uranium dissolved from the flotation concentrate was recovered by ion exchange. The small amount of copper solubilized with the uranium was recovered as cement copper by the addition of powdered iron to the ion exchange barren solution. El Paso reported in 1964 that the Orphan Lode ore averaged about 1.3% Cu and that 75 percent of the total copper or 90 percent of the sulfide copper was recovered. The copper concentrate averaged 20% Cu and 10 ounces of silver per ton in the sulfides. The cement copper averaged 55% Cu. Both products were shipped by truck to the smelter at Inspiration, Arizona. No other data are available on the copper production at the Tuba City mill.

Rare Metals and El Paso always sought to provide employment opportunities for the Navajo Indians, as evidenced by the mill complement that routinely was two-thirds or more Navajos.

Tables 1 and 2 present data on the AEC purchases of U3O8 from Rare Metals' and El Paso's Tuba City operation and mill production data during the term of the AEC contracts.

Table 1 - AEC Purchases of U-O- from El Paso Natural Gas Co.-Tuba City, AZ

Contract No.    Period (FY) U3O8 (Lbs.) Average Cost Per Lb. U3O8 ($)
AT(05-l)-293 1957(a)-1962 2,698,493 10.88
AT(05-1)-910 1963-1967(b) 1,999,868 8.00
Total 1957 - 1967 4,698,361 9.65(c)
a) First U3O8 delivered 7/56.
b) Last U3O8 delivered 11/66.
c) Average Fiscal Year costs ranged from $7.98 to $12.84.  

Table 2 - Mill Production Data - El Paso Natural Gas Co.-Tuba City, AZ

Period of Operation  AEC Contracts
Uranium Ore 6/56 - 9/66 (1)
Fed to Process (Tons)  796,489
U3O8 (%)  0.33
U3O8 (Lbs.)  5,233,029
U3O8 in Conc. (Lbs.)  4,696,402
U3O8 Recovered (%)  90
U3O8 Shipped to AEC (Lbs.)  4,696,402
U3O8 Shipped to Others (Lbs.) 0

(1) Ore was fed to process from Jxme 4, 1956 through May 1962 and from April 1963 through September 1966. Concentrate was produced from plant inventories in October and November 1966.

After the mill shut down all of the mill equipment and most of the buildings were removed from the site. The structural steel frame of the main mill building and the concrete block office building remain, as well as the houses in the housing area.

The tailings, consisting of three connected piles, are located south of the mill building. Approximately 800,000 tons of tailings remain at the site. A chemical stabilizer was applied to the surface of the tailings in 1968, but has since been determined to be ineffective in preventing wind transport of the tailings. As noted earlier, the site has been designated for remedial action and has been given a "medium" priority.

Although there is no record of tailings being removed from the site, mobile gamma radiation surveys have detected some anomalies in the housing area and in Tuba City. The DOE, through follow-up surveys, will determine the vicinity propertied to be designated for remedial action."



DOE Legacy Management has a webpage on the Uranium Mill at Tuba City.


  • Rare Metals Corporation of America
  • El Paso Natural Gas Company
  • DOE Contracts Numbers

  • E(05-1)-1658
  • AT(05-1)-293
  • AT(05-1)-910


    DOL provides Part B and E payment statistics on the Tuba City Uranium Mill as well as a Site Exposure Matrix.


    NIOSH provides payment statistics on dose reconstructions for the Tuba City Uranium Mill.


  • The Wall Street Journal Waste Lands series provides additional information on the Tuba City Mill Site


  • Summary of the Phase II Title 1 Engineering Assessment of Inactive Uranium Mill Tailings Tuba City Site Arizona; 1977 
  • Phase 2 Engineering Assessment of Inactive Uranium Mill Tailings Tuba City, AZ; 1977
  • Summary Engineering Assessment of Inactive Uranium Mill Tailings Tuba City, AZ.; 1981
  • Engineering Assessment of Inactive Uranium Mill Tailings Tuba City Site Arizona; 1981
  • Estimated Population Near Uranium Tailings; 1984


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     Photos courtesy of DOE and Library of Congress