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Baseline Risk Assessment of Groundwater Contamination at the Uranium Mill Tailings Site Near Gunnison, Colorado

Description: This Baseline Risk Assessment of Groundwater Contamination at the Uranium Mill Tailings Site Near Gunnison, Colorado evaluates potential impacts to public health or the environment resulting from groundwater contamination at the former uranium mill processing site. The tailings and other contaminated material at this site are being placed in an off-site disposal cell by the US Department of Energy`s (DOE) Uranium Mill Tailings Remedial Action (UMTRA) Project. Currently, the UMTRA Project is evaluating groundwater contamination. This is the second risk assessment of groundwater contamination at this site. The first risk assessment was performed primarily to evaluate existing domestic wells. This risk assessment evaluates the most contaminated monitor wells at the processing site. It will be used to assist in determining what remedial action is needed for contaminated groundwater at the site after the tailings are relocated. This risk assessment follows an approach outlined by the US Environmental Protection Agency (EPA). The first step is to evaluate groundwater data collected from monitor wells at the site. Evaluation of these data showed that the main contaminants in the groundwater are cadmium, cobalt, iron, manganese, sulfate, uranium, and some of the products of radioactive decay of uranium.
Date: December 1, 1993

Baseline Risk Assessment of Groundwater Contamination at the Uranium Mill Tailings Site Near Gunnison, Colorado. Revision 1

Description: This report evaluates potential impacts to public health or the environment resulting from groundwater contamination at the former uranium mill processing site. The tailings and other contaminated material at this site are being placed in an off-site disposal cell by the US Department of Energy`s (DOE) Uranium Mill Tailings Remedial Action (UMTRA) Project. Currently, the UMTRA Project is evaluating groundwater contamination. This is the second risk assessment of groundwater contamination at this site. The first risk assessment was performed primarily to evaluate existing domestic wells to determine the potential for immediate human health and environmental impacts. This risk assessment evaluates the most contaminated groundwater that flows beneath the processing site towards the Gunnison River. The monitor wells that have consistently shown the highest concentration of most contaminants are used in this risk assessment. This risk assessment will be used in conjunction with additional activities and documents to assist in determining what remedial action is needed for contaminated groundwater at the site after the tailings are relocated. This risk assessment follows an approach outlined by the US Environmental Protection Agency (EPA). The first step is to evaluate groundwater data collected from monitor wells at the site. Evaluation of these data showed that the main contaminants in the groundwater are cadmium, cobalt, iron, manganese, sulfate, uranium, and some of the products of radioactive decay of uranium.
Date: April 1, 1994

Gunnison, Colorado, Subpile Study Report

Description: To protect human health and the environment, the UMTRA project will remediate the uranium mill tailings site at Gunnison, Colorado. There are explicit requirements (i.e., 40 Part CFR Part 192) for the surface remediation of radiologically contaminated soils on UMTRA sites. The removal of subpile sediment to the depth required by 40 CFR Part 192 will leave in place deeper foundation sediment that is contaminated with hazardous constituents other than radium-226 and thorium-230. The Department of Energy and the Colorado Department of Health have questioned whether this contaminated soil could potentially act as a continuing source of ground water contamination even after surface remediation based on 40 CFR Part 192 is complete. To evaluate the subpile sediments as a potential source of ground water contamination, the Gunnison subpile study was initiated. This report summarizes the results and findings of this study.
Date: March 1, 1994

Mitigation and Monitoring Plan for Impacted Wetlands at the Gunnison Umtra Project Site, Gunnison, Colorado. Revision 1

Description: The Gunnison, Colorado, abandoned uranium mill site is one site being cleaned up by the DOE under UMTRCA authority. This site`s contaminated material is being transported to a disposal site on US Bureau of Land Management (BLM) land east of Gunnison. Remedial action activities have temporarily disturbed 0.8 acre (ac) (0.3 hectares [ha]) of wetlands and permanently eliminated 4.3 ac (1.7 ha). As required by the Clean Water Act, the US Army Corps of Engineers (USACE) prepared a Section 404 Permit that addresses the loss of wetlands as a result of remedial action at the Gunnison UMTRA Project site. The 404 permit includes this report as an attachment and it describes the wetland mitigation and monitoring plan. The DOE formulated this plan in consultation with the BLM and the USACE. This report represents a revised version of the mitigation and monitoring plan (DOE, 1992b).
Date: December 1994

Site-Specific Analysis of Radiological and Physical Parameters for Cobbly Soils at the Gunnison, Colorado, Processing Site. Revision 1

Description: The remedial action at the Gunnison, Colorado, processing site is being performed under the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978. Under UMTRCA, the US Environmental Protection Agency (EPA) is charged with the responsibility of developing appropriate and applicable standards for the cleanup of radiologically contaminated land and buildings at 24 designated sites, including the Gunnison, Colorado, inactive processing site. Section 108 of Public Law 95-604 states that the US Department of Energy (DOE) shall ``select and perform remedial actions at the designated processing sites and disposal sites in accordance with the general standards`` prescribed by the EPA. Regulations governing the required remedial action at inactive uranium processing sites were promulgated by the EPA in 1983 and are contained in 40 CFR Part 192 (1993), Health and Environmental Protection Standards for Uranium and Thorium Mill Tailings. This document describes the radiological and physical parameters for the remedial action of the soil.
Date: January 1, 1994

Surface and subsurface cleanup protocol for radionuclides, Gunnison, Colorado, UMTRA project processing site. Final report: Revision 1

Description: Surface and subsurface soil cleanup protocols for the Gunnison, Colorado, processing site are summarized as follows: In accordance with EPA-promulgated land cleanup standards, in situ Ra-226 is to be cleaned up based on bulk concentrations not exceeding 5 and 15 pCi/g in 15-cm surface and subsurface depth increments, averaged over 100m{sup 2} grid blocks, where the parent Ra-226 concentrations are greater than, or in secular equilibrium with, the Th-230 parent. In locations where Th-230 has differentially migrated in subsoil relative to Ra-226, a Th-230 clean up protocol has been developed. The cleanup of other radionuclides or nonradiological hazards that pose a significant threat to the public and the environment will be determined and implemented in accordance with pathway analysis to assess impacts and the implications of ALARA specified in 40 CFR Part 192 relative to supplemental standards.
Date: December 1993
Creator: Gonzales, D.

Umtra Project Water Sampling and Analysis Plan, Gunnison, Colorado: Revision 1

Description: This water sampling and analysis plan summarizes the results of previous water sampling activities and the plan for future water sampling activities, in accordance with the Guidance Document for Preparing Sampling and Analysis Plans for UMTRA Sites. A buffer zone monitoring plan for the Dos Rios Subdivision is included as an appendix. The buffer zone monitoring plan was developed to ensure continued protection to the public from residual contamination. The buffer zone is beyond the area depicted as contaminated ground water due to former milling operations. Surface remedial action at the Gunnison Uranium Mill Tailings Remedial Action Project site began in 1992; completion is expected in 1995. Ground water and surface water will be sampled semiannually at the Gunnison processing site and disposal site. Results of previous water sampling at the Gunnison processing site indicate that ground water in the alluvium is contaminated by the former uranium processing activities. Background ground water conditions have been established in the uppermost aquifer at the Gunnison disposal site. The monitor well locations provide a representative distribution of sampling points to characterize ground water quality and ground water flow conditions in the vicinity of the sites. The list of analytes has been modified with time to reflect constituents that are related to uranium processing activities and the parameters needed for geochemical evaluation.
Date: November 1994