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_` COLORADO LEGACY LAND <br /> SCHWARTZWALDER MINE <br /> gamma radiation survey (Fall 2021) and shows the location of the Ore Sorter Decommissioning Area (also <br /> called RML Area#2). CLL does not anticipate excavation to extend into Ralston Creek. The vertical extent of <br /> contamination may extend to bedrock (approximately 15 feet below ground surface or less) in some areas, <br /> particularly on the south/southeastern portion of the excavation area near RML Area#2. <br /> As indicated in Technical Revision 14,alluvial materials with Radium-226 concentrations above 7 pCi/g shall <br /> be excavated and disposed of to protect water quality in Ralston Creek. Alluvial materials with Radium-226 <br /> concentrations below 7 pCi/g are expected to meet the 17.2 mg/kg natural-uranium criterion,which in turn, <br /> should ensure that groundwater leachate from contact with alluvial fill materials will not exceed the applicable <br /> water quality standard of 0.03 mg/L. <br /> In the course of the alluvial valley excavation project,CLL has learned that contaminated soils (concentration <br /> of radium-226 greater than 7pCi/g) occur in"pockets"adjacent to unimpacted soils (concentration of radium- <br /> 225 less than or equal to 7pCi/g). This deposition is considered reflective of the historic ore-sorting practices <br /> that created the initial contamination. These unimpacted soils may be used a fill materials or growth media for <br /> reclaiming the valley or capping the expanded SWRP. Reclaiming with local soils is expected to reduce the <br /> likelihood of importing weeds or invasive species from outside fill material. Regrading is expected to occur <br /> consistent with Figure F-2 with a final slope of 3HAV or less with positive drainage toward Ralston Creek. <br /> Successful completion of alluvial fill excavation work (i.e. confirmation that all contaminated soils have been <br /> removed)shall be verified with soil sampling results and presented in a Final Status Survey Report,which shall <br /> be provided under separate over to DRMS and CDPHE to satisfy the following regulatory requirements: <br /> • DRMS: Remove soil with the potential to leach uranium to surface water above the Colorado domestic <br /> water supply limit for uranium [0.03 mg/L].The objective is to protect water quality in Ralston Creek <br /> and satisfy reclamation requirements under the Mine Permit(M-1977-300). <br /> • CDPHE WQCD: Eliminate the discharge of uranium and other mine-related pollutants from "the Pad" <br /> to alluvial groundwater and surface water in Ralston Creek.The removal of contaminated alluvial fill <br /> materials is expected to eliminate the long-term need to operate the sump-capture system and bypass <br /> pipeline, and to eliminate the need for monthly monitoring of Ralston Creek as required by the <br /> NOV/CDO(CDPHE,2010). <br /> • CDPHE Radiation Control Program: Remove soil above CDPHE clean-up requirements for unrestricted <br /> release of RML Area #2 (also called the Ore Sorter Decommissioning Area in Exhibit U) from <br /> Radioactive Materials License CO-369-06. <br /> AUGUST 2022 13 AMENDMENT 6 <br />