|
Green
River Concentrator Site
Grand County, Utah
| Years of Operation |
Status of Mill
or Plant Site |
Uranium Ore
Processed
(Million Short Tons) |
Production
(Million Pounds U3O8) |
| 1958-1961 |
Decommissioned |
0.18 |
0.83 |
Remediated
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) |
| 25 |
6 |
0.38 |
30 |
76 |
23.63 |
Location: The Green River concentrator site is located in Grand County, Utah, and about one-half mile east of the Green River, one mile southeast of the City of Green River, Emery County, Utah.1
Background: The Green River concentrator was built by Union Carbide Corporation (UCC) in early 1958 and was operated from March of that year to January 1961. The original site covered about 80 acres. The plant shipped uranium concentrate and carbon concentrate products by rail to the UCC uranium mill at Rifle, Colorado, for final processing. Feed to the Green River concentrator plant consisted of sandstone-type ore that contained between 0.27 and 0.30 percent U3O8. The ore was poorly cemented with clay and asphaltic materials, and part of the uranium was contained in the carbonaceous fraction. The carbonaceous fraction was recovered separately by screening and flotation of the ground ore. The flotation product was stockpiled for later treatment. (Removing the carbonaceous fraction was necessary to prevent problems in processing the Green River product at the Rifle, Colorado, mill.) The remaining ground, coarse-ore fraction was mixed with recirculated acid solution and a sand-slimer separation was then made on this slurry. The sand fraction was then acid leached, and uranium was precipitated from the pregnant solution. The precipitate was mixed with the remainder of the primary slimes, and that product was dewatered, dried, and shipped to the Rifle mill. The concentrator processed uranium ore at an average rate of about 200 tons per day (TPD). Over the concentrator’s operating life, a total of some183,400 tons of ore averaging 0.26 percent U3O8 was processed. The concentrator also recovered vanadium from the ore, which averaged about 1.00 percent V2O5. Recovery of U3O8 averaged 87 percent; data for vanadium recovery are not available. Ore for the concentrator came primarily from mines in the Temple Mountain area of the San Rafael Swell and Green River districts in Emery County, Utah. Some 137,000 tons of tailings were generated by the concentrator over its operating life. Later, a flash flood swept away about 14,000 tons from the tailings pile, and in 1982 the pile was estimated to contain about 123,000 tons of tailings. After the concentrator was closed down, the 9-acre tailings pile was stabilized with a 6-inch thick earthen cover. An onsite pond was positioned to collect surface rainwater runoff from the pile. Later, buildings remaining at the site were used by the U.S. Army’s Utah Launch Complex of the White Sands Missile Range in New Mexico. The State of Utah acquired the concentrator plant site from UCC in 1988.
|
|
UMTRA Surface Remediation: Remediation involved relocating and stabilizing the residual radioactive material, including material from 17 vicinity properties, into an onsite, engineered disposal cell. Materials from the mill-tailings pile, the decontaminated debris from the demolition of onsite concentrator-plant structures, and the contaminated soils and debris from cleanup of the vicinity properties were relocated to the disposal cell.
Disposal Area: In 1988-1989, the Department of Energy (DOE) consolidated the radioactive materials in a new disposal cell, which conforms with EPA standards. The 6-acre cell is sited on a flood plain of a local stream about 500 feet south of the original tailings pile site. The cell was dug to bedrock in predominantly fluvial mudstone strata and was lined with 6 feet of clean low permeability soil. Most of the radioactive materials were emplaced to lie below the local natural-surface grade. The cell is capped by a 4.5-foot thick multilayered cover. A 3-foot thick compacted clay layer was placed directly on the contaminated materials and serves as the low permeability radon barrier and also minimizes infiltration of rainwater into the cell. Below grade, the clay layer extends out over the sides of the cell. Above grade, a 6-inch granular bedding layer was placed on top of the radon barrier to promote rapid surface drainage and protect the barrier from the 1-foot thick riprap cover. The Nuclear Regulatory Commission (NRC) certified the disposal cell in July 1992. When NRC agreed in 1998 that the site met the cleanup standards and accepted the proposed long-term surveillance plan, the Green River site came under a general license for custody and long-term care.
Responsibility for Remediation: A cost sharing arrangement, defined under a Cooperative Agreement with the State of Utah, made DOE responsible for all assessment costs and 90 percent of site remediation costs. DOE also was responsible for 90 percent of the State of Utah’s 10 percent, which made the State responsible for 1 percent of remediation costs.
Stewardship: The disposal cell site is being managed under the DOE’s Long-Term Surveillance and Monitoring (LTSM) Program in accordance with the approved site specific plan. DOE will be responsible in perpetuity for the safety and integrity of the Green River site.
Groundwater Program: Groundwater at the Green River concentrator site was found to be contaminated with residual materials generated during the uranium ore processing at the site. This contamination extends downward into the uppermost undisturbed strata below the site. The full extent of groundwater contamination from milling activities is not known. Data from groundwater monitoring will be required to fully characterize local groundwater conditions and for the development of a compliance strategy for regulatory approval. DOE will monitor groundwater quarterly at the disposal cell through at least 2001 to assure that the waste material encapsulated in the disposal cell continue to remain isolated from the groundwater aquifers. The aquifers at the site have low water yields, and the water is not suitable for agricultural or domestic use due to natural contamination including elevated levels of selenium. The aquifers are not a current or potential source of drinking water, as defined in CFR Part 192, and remediation of the groundwater is not planned. After 2001, groundwater monitoring may be reduced in frequency following program reevaluation. Current planning assumes groundwater monitoring will continue once every 5 years until 2018.
|
|
