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Decommissioning Plan Schwartzwalder Mine RML CO-369-06 Cotter Corporation (N.S.L.) 7 March 2017 2.0 CURRENT CONDITIONS As detailed in Section 1.3, the current site conditions include a new water treatment plant (RML #4) and the OWTP building and the Barrens Ponds (RML #2). All other features covered under the License have been decommissioned and released from RML #2. The remainder of the mine site reclamation is being conducted under DRMS reclamation permit M-77-300. An Environmental Report was submitted as part of the license renewal effort in 2005 (Cotter, 2005). The report covers the environmental setting for the Mine and is incorporated here by reference. 2.1 Constituents of Concern Constituents of concern with respect to the RML include radiological contamination in soils or on building surfaces. Radionuclides of concern are primarily limited to uranium-238 (U-238) and its radiological decay products. Uranium-238 decay products include long-lived Th-230 and Ra-226, as well as short-lived progeny of Ra-226 (e.g. Rn-222, Po-218, Pb-214, Bi-214, and Po - 214). Principal radiations of concern include alpha particles (for internal doses) and gamma radiation (for external doses). Radium-226 in soil is an important radionuclide with respect to cleanup criteria at uranium recovery sites because it is long lived (approximately 1,600-year half-life), governs concentrations of short-lived higher-activity decay products (including radon gas), and is readily detected with gamma survey instruments. The uranium isotopes found in natural uranium (U- 238, U-234, and U-235) have comparatively low radioactivity, but can present toxicity issues at sufficiently high concentrations. The radioactive decay products associated with natural uranium ores typically exist in approximate secular equilibrium (approximately equal radioactivity concentrations). This assumption was made in conducting a dose assessment for remedial options surrounding cleanup of the OTP (Shepherd Miller, 1997). Confirmation sampling data collected as part of the OTP cleanup (Cotter, 1998) generally support the assumption of equilibrium. In RML #3 (the drying trenches), both Ra-266 and uranium in surface soil samples were evaluated and results indicate that remediation based on the Ra-226 successfully addressed residual uranium as well. This makes sense as the drying trench area contained water treatment solids that were presumably depleted in uranium relative to Ra-226 due to the barium chloride water treatment process. For RML #2, equilibrium among U-238 decay series radionuclides was assumed for development of soil cleanup criteria (Section 3.2) based on scoping survey soil sampling data collected in this area in 2008 (Section 2.5, Table 1). Given the relative abundances of uranium isotopes in natural uranium (U-nat), the ratio of U-nat to Ra-226 should be about 2 when approximate equilibrium across U-238 decay produces exists. Aside from the one clearly anomalous ratio (for a sample taken near the centerline between the two retention ponds), the average U-nat / Ra-226 ratio in samples in the vicinity of RML #2 was 2.1 (Figure 6). Taking