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Technical Revision 25, Rev. I Schwartzwalder Mine <br /> 2.2.3 Soil Cleanup Criteria <br /> As described in the Schwartzwalder RML decommissioning plan, Cotter performed a number of <br /> analyses using RESRAD to determine acceptable doses to various members of the public <br /> including: a residential farmer, commercial business, and recreational user(Cotter 2017). These <br /> analyses incorporated the gamma and soils radiological data discussed above, as well as other <br /> factors such as meteorology and time spent onsite. <br /> Results of these analyses indicate that a radium-226 concentration of 7.1 pCi/g will result in a <br /> dose of 21.4 mrem/year, which is below the 25 mrem/year limit for unrestricted use. Therefore, <br /> 7.1 pCi/g radium-226 is the cleanup standard for RML#2. According to analyses performed by <br /> Cotter, 7.1 pCi/g is equivalent to 22 µR/hr, which will be Cotter's screening criteria to determine <br /> whether or not soils will be sent to the waste rock piles or to the Minnesota Adit. Cotter will <br /> perform additional sampling and analysis to confirm the radium-226/gamma exposure rate <br /> relationship. <br /> 2.3 EXCAVATION METHOD AND SURVEYS <br /> - Within RML #2, Cotter will establish a 10-m x 10-m grid, which will be used to guide the <br /> excavation. The general excavation sequence will include gamma scanning followed b <br /> g g Y <br /> excavation of a 2-foot lift. For example, Cotter will perform an initial scan to identify those <br /> grids meet or exceed the screening criteria. Then Cotter's contractor will excavate 2 feet of <br /> alluvial material. <br /> Materials from those grids that meet the screening criteria will be placed onto the waste rock <br /> piles. Conversely, materials from those grids that exceed the screening criteria will be placed <br /> into the Minnesota Adit. This process will continue for all subsequent lifts. Cotter will <br /> document the final placement of each grid for each lift and calculate the final volumes of <br /> material placed in the waste rock piles and the Minnesota Adit. Cotter estimates that a maximum <br /> of 7,200 cy will be placed into the Minnesota Adit. Cotter will perform and document a final <br /> status survey for the excavation pursuant to the decommissioning plan. <br /> 2.4 AMENDED ATTACHMENT F <br /> - Cotter has included an amended Attachment F to TR-23. This amendment includes 5 tables of <br /> materials that will be placed into the Minnesota Adit. Table 5 has been amendment to include <br /> 7,200 cy of alluvial materials from RML #2. <br /> Mine Permit M-1977-300 <br /> Cotter Corporation(N.S.L.) 9 June 2017 <br />