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Cotter Corporation Cañon City Uranium Mill Site Summary

The Cotter/Lincoln Park site consists of a uranium processing mill located adjacent to the unincorporated community of Lincoln Park, and is approximately 1 ½ miles south of Cañon City. The entire site is within Fremont County. The mill operated continuously from 1958 until 1979, and intermittently since that time. Operations are regulated primarily by a Colorado Radioactive Materials License. Mill operations have released radioactive materials and metals into the environment. These releases contaminated soil and groundwater around the mill and the Lincoln Park area.


The Cotter/Lincoln Park Site was added to the U.S. Environmental Protection Agency’s (EPA) National Priorities List in 1984 (making it a Superfund site). EPA divided the site into two “operable units,” one being the sources of contamination on the mill site, such as the old ponds area and the other being the Lincoln Park neighborhood (off-site impacts). Cleanup activities to date have focused on eliminating the mill site as a source of contamination to Lincoln Park, and eliminating exposures to Lincoln Park residents. 


The contaminants of most concern at the site are molybdenum and uranium. Exposure to molybdenum can cause gout-like symptoms. Uranium is a radioactive metal that can be toxic to the kidneys. The primary exposure pathways would be drinking contaminated water and inhaling contaminated dust. Radon, a decay product in the uranium chain, is also of potential concern. Radon is a gas that has been linked to lung cancer.


In 1988, the State of Colorado settled a lawsuit for natural-resource damages with Cotter. As part of the settlement, the State and Cotter agreed on required site characterization and cleanup activities. These requirements are contained in the 1988 Remedial Action Plan (RAP). Major cleanup activities performed since 1988 include:


  • Connecting Lincoln Park residents to city water;
  • Constructing a ground-water barrier at the Soil Conservation Service (SCS) dam to minimize migration of contaminated ground water into Lincoln Park;
  • Moving tailings that remained after 1981-1983 cleanup activities and contaminated soils into a lined impoundment to eliminate them as a source of contamination; and
  • Excavating contaminated stream sediments in Sand Creek 


Cotter also voluntarily cleaned up several railroad loading areas around Cañon City, where uranium ore and other materials had been spilled.


The large majority of work under the Remedial Action Plan has been completed. One cleanup element that has not been completed is flushing contamination out of the Old Tailings Pond area. Although Cotter has tried several pilot tests, none has been successful. Cotter and the state continue to have discussions regarding this cleanup element. It should be noted that contaminated groundwater from this area is captured at the Soil Conservation Service dam and pumped back to the lined impoundments.


Cleanup activities under the Remedial Action Plan have shown positive results. Since 1988 the contaminated groundwater plume in Lincoln Park has shrunk in size. In addition, at many locations within the plume, concentrations of contaminants have decreased. Descriptions of the continued operation of remedy components and monitoring data are included in an annual report produced by Cotter in June of each year.


EPA required Cotter to address contaminated groundwater that was bypassing the Soil Conservation Service (SCS) dam barrier.  A 1999 Focused Feasibility Study analyzed options, and Cotter constructed a Permeable Reactive Treatment Wall (PRTW) downstream of the dam to treat this water in 2000. The wall performed well for approximately eighteen months, but then began to plug up.  Cotter is currently pumping this water back behind the dam while it evaluates how to fix the treatment wall.

The Cotter Uranium Mill was originally licensed in 1958 by the Atomic Energy Commission. In 1968 the Colorado Department of Health took over these licensing responsibilities. The license addresses safe operation of the mill in terms of both worker safety and environmental emissions, and final decommissioning and cleanup of the site. Final cleanup requirements for the mill site (known also as the Superfund site Operable Unit #1) will be coordinated between EPA and the State, and included as license conditions. This cleanup will include all contaminated onsite processing areas and windblown soils.


In 1995, a license amendment was filed with the state for alkaline leach processing of uranium ore. This amendment became effective in February 1997. In December 2000, Cotter filed a license renewal application in a timely manner prior to their license expiration that allowed them to continue to operate under their existing license until a new license is put in place. In that same year, Cotter also started testing a new process that recovers zirconium along with uranium from different types of ore. License review and discussions occurred until June 2002 when the Department of Public Health and Environment rejected the application as incomplete and required an improved submittal. Collaborative efforts continued to resolve deficiencies, and in September 2003, Cotter submitted a revised application.


A renewed license was issued in December 2004 that continued operation of the uranium mill but disallowed acceptance of wastes for disposal in the impoundment. Cotter appealed the waste denial; however, the Department decision was upheld and Cotter ceased the appeal in 2008.


In early 2006, Cotter ceased normal operations and stabilized the facility to go into a "stand down" condition.