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White Canyon Mill Site
White Canyon,
San Juan County, Utah
| Years of Operation |
Status of Mill
or Plant Site |
Uranium Ore
Processed
(Million Short Tons) |
Production
(Million Pounds U3O8) |
| 1949-1953 |
Dismantled |
0.03 |
0.13 |
Mill/Plant
Area
(Acres) |
Disposal Cell
Area
(Acres) |
Disposal Cell
Radioactive
Waste
Volume
(Million Cubic Yards) |
Disposal Cell
Total Radioactivity
(Ci, 226Ra) |
Disposal Cell
Average Tailings
Radioactivity
(pCi/g, 226Ra) |
UMTRA Project
Final Cost
(Million Dollars) |
| NA |
NA |
NA |
NA |
NA |
NA |
Location:
The former White
Canyon uranium mill site was located near the old town of . . . "Hite
in southeastern Utah where White Canyon intersects the Colorado River."1
In 1965, Lake Powell inundated the site, and it was not included in the
remedial action program for inactive uranium mills.
Background:
Mining of radioactive mineral deposits in the Triassic rocks of the Colorado Plateau region of Utah was a small though important industry
in the early 1900s. By 1912 in the San Rafael Swell area of Emery County, Utah, high grade uranium-vanadium ores were being mined from deposits
exposed on Chinle Formation outcrops and in shallow mine openings. During World War I, similar deposits were also mined in the Temple Mountain, Utah, area. The U.S. Bureau of Mines in 1912 undertook a broad field study of the Green River and San Rafael Swell mining areas to examine the production of uranium and vanadium ores in the hope of increasing the efficiency of uranium mining practices then being used.2 At the time, the carnotite deposits of southwestern Colorado and southeastern Utah were considered . . . "the most important uranium-bearing deposits in the world."3 The chief prize of production was radium, and the uranium ore deposits in the West were being "high graded" in order to obtain ore of sufficient metal content to merit shipment to the eastern United States and to Europe. The Bureau was concerned about mining methods that, while yielding a shipping-grade ore, in practice were wasteful of the small uranium resources known at that time. For every ton of ore shipped to market, up to five tons of low grade ore were being sent to waste dumps. Further, the "high grading" effectively eroded the quality and quantity of the unmined part of a deposit and rendered any potential future ore production even more difficult and costly.
In the period 1920-1940, the U.S. Geological Survey conducted a reconnaissance field program to describe the geology and rocks and evaluate the potential oil and gas resources of a broad area in eastern Utah and northeastern Arizona.4 Uranium, vanadium, and copper minerals were noted in many places in the Triassic rocks throughout the region, especially near the unconformable contact between the Moenkopi Formation (Early and Middle(?) Triassic age) and the Chinle Formation (Late Triassic age). Beginning in the late 1940s, the results of this work and other background information contributed to discovery by private industry of uranium deposits in the Triassic strata of southeastern Utah, including those in the White Canyon-Red Canyon uranium district of southeastern Utah.
The White Canyon-Red Canyon district, San Juan County, is situated along the western flank and crest of the Monument Upwarp, where sedimentary rocks of Permian to Jurassic age are deeply eroded and exposed in canyons of the major drainages that formed along the upwarp's axis. In the district, about 40 miles long by up to 20 miles wide, uranium-bearing strata occur mainly in the Shinarump Member (basal unit of the Chinle Formation) which lies unconformably on top of the Moenkopi Formation. The ore deposits are irregularly distributed in the Shinarump and occur largely in sandstone and conglomeratic strata that fill stream channels and scours that were eroded in Middle Triassic time into underlying sandstone-siltstone strata of the Moenkopi Formation. Some Shinarump paleochannels are locally more than 120 feet deep, and in places they cut through the Moenkopi and into the underlying Permian strata. The ore deposits are generally tabular in shape and are elongated with the trend of the hosting paleochannel strata. In most uranium deposits, the grade of the mineralization varies strongly over short distances, and adjacent deposits within the same channel commonly are separated by barren rock. The ore grade in mined deposits was between 0.20 and 0.30 percent U3O8 on average. Some deposits also contained copper and others vanadium as a co-product. Locally, uranium ore was also mined from the uppermost Moenkopi beds where the mineralization extended downward from the overlying Shinarump channel uranium deposits.
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From the early 1930s through 1945, several uranium deposits in the southeastern Utah-northeastern Arizona region were mined principally for their co-metal content. A large Shinarump-hosted deposit (discovered in 1921) in the Monument Valley area of northeastern Arizona was first mined for vanadium in 1942. A few carloads of copper-uranium ore reportedly were mined in about 1944 from the Happy Jack mine in the White Canyon district and shipped to the Garfield smelter in Salt Lake County, Utah, for recovery of the copper.
In May 1949, the U.S. Atomic Energy Commission entered into a contract with the Vanadium Corporation of America (VCA) to purchase uranium concentrates from a new mill to be built and operated near the mouth of White Canyon across the Colorado River from Hite, Utah.5 The contract's original termination date was June 30, 1953, but the mill was operated under several extensions through December 31, 1953. The small mill, essentially a pilot-scale operation, began operating in mid 1949, and its first concentrate delivery to the AEC occurred in late 1949. The mill was shut down at the end of 1953.
The mill processed copper- uranium ore from nearby mines of the White Canyon district. The Happy Jack mine shipped its first uranium ore in April 1949 to the new mill, and it continued to supply a substantial amount of ore to the mill throughout its operating life.6 More than 95 percent of the ore processed at the mill during the contract term was purchased by VCA from local independent ore producers: VCA furnished the remainder. The mill used an acid-leach process, with neutralization of the leach liquor by sodium carbonate. This formed an alumina sludge that was separated from the leach liquor. Addition of a small amount of caustic to the clarified pregnant solution resulted in precipitation of uranium as sodium diuranate, which was then filtered, dried, and packed for shipping. Over its operating life, the mill treated 26,358 tons of ore averaging 0.43 percent U3O8. All uranium concentrate produced at the mill, 128,145 pounds U3O8, was sold to the AEC. The mill's average ore-processing rate was about 20 tons of ore per day (TPD). Over the final three years of milling operations, the average uranium-recovery rate was about 70 percent. Given the small size of the White Canyon milling operation and the low copper content in the ore processed (less than 0.4 percent copper), the recovery of co-product copper was not justified. On average, 43 percent of the ore's uranium was not recovered, but remained in the mill tailings impounded at the mill site.
After its contract for the sale of uranium concentrate to the AEC expired in 1953, the White Canyon mill was shut down. The mill was dismantled by VCA in about 1954. Based on the quantity of ore treated at the mill, the AEC estimated that some 26,000 tons of tailings were originally impounded at the mill site. In November 1963, when the future Lake Powell was scheduled to begin forming behind the Glen Canyon Dam, the AEC requested the Department of Health, Education, and Welfare to determine what would be the future radiation effect of the White Canyon mill tailings, which contained an estimated 13 grams of radium-226, when flooded by the lake. The study concluded that, given the isolated location of the site and the dilution factor represented by the large volume of water in the lake, the mill tailings could remain at the former mill site and be inundated by the lake waters. It was postulated that, after a period of years, the natural action of sedimentation in the lake would cover the tailings under several feet of silt. After the study, VCA in the mid 1960s removed some "high grade" tailings material from the former mill site and presumably reprocessed those tailings at its Shiprock, New Mexico, mill.
The former mill site and the old tailings pile were covered by rising waters of Lake Powell in 1965. In October 1965, when the tailings were inundated, a series of water and bottom sediment samples were collected in the immediate vicinity of the tailings pile and also at intervals over a distance of several miles both upstream and downstream from the mill site. The old White Canyon tailings pile was determined to be covered with sediment distributed by the lake water. Further analyses of both the lake water and bottom sediment samples determined there was no significant variation in the levels of radioactivity between the samples collected upstream and downstream from the tailings site and from over the tailings site.
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