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_•� COLORADO LEGACY LANL? <br /> $CHWARTZWALDER MINE <br /> TABLE E-3:SUMMARY OF WATER TREATMENT PLANT OPERATIONS FOR THREE CONSECUTIVE YEARS <br /> WTP Operations Dissolved Mine Pool <br /> Year Uranium Dewatering Notes <br /> Summary (mg/L) Summary <br /> Operated 47%of the year. Feet Gained=51 feet <br /> 2018 Online= 171 days. 12.19 Max.Depth=201 fbS In-situ injection in <br /> December 2017. <br /> Offline= 194 days. (6,251 ft amsl) <br /> Operated 66%of the year. Feet Gained=46 feet Installed new 60 hp <br /> 2019 Online= 241 days. 13.73 Max.Depth=246 fbS dewatering pump <br /> Offline= 124 days. (6,206 ft amsl) at—400 fbS. <br /> Operated 47%of the year. Feet Gained=99 feet <br /> 2020 Online= 172 days. 12.56 Max.Depth=345 fbS In-situ injection in <br /> Offline= 194 days. (6,107 ft amsl) January 2020. <br /> Notes: <br /> 1 Mean concentration of mine pool sample results.For comparison,the mean concentration of uranium <br /> in the mine pool from 2000-2007 was 41.14 mg/L.(Source:Whetstone Associates.2007.) <br /> -Approximately <br /> amsl-Above mean sea level <br /> fbS-Feet below Steve Level <br /> ft amsl-Feet above mean sea level <br /> mg/L-milligrams per liter <br /> WTP-Water Treatment Plant <br /> E.5.3. Tracer Test <br /> During 2020,a two-chemical tracer test was conducted in the mine to evaluate the system hydraulics and the <br /> degree that organic carbon placed underground would disperse within the mine workings to facilitate in-situ <br /> treatment.A complete description of the tracer test is provided in Appendix 2.During the duration of the tracer <br /> test,there was no flow leaving the mine as confirmed by the mine pool elevation being consistently below the <br /> regulatory limit.Based on the absence of tracer concentrations in the WTP discharge,the tracers remained in <br /> the mine.Therefore,the mine is a hydrologic sink,e.g.,mine pool water is not exiting the mine. <br /> E.5.4. Water Treatment Plant Operating Strategy <br /> CLL is planning to operate the WTP seasonally for approximately six months to manage the mine pool. As <br /> described above,shutting the WTP down for at least six months is based on empirical data with a conservative <br /> factor included. However,as more data are collected and the mine pool level maximized below the regulatory <br /> limit,the shut down period may be extended beyond six months.Regardless of the shut down period,the mine <br /> pool level will be monitored to ensure the regulatory limit is not exceeded.The months of operating the WTP <br /> are anticipated to be during the time of year in which access to the Schwartzwalder Mine is generally not <br /> hampered by weather. During operations, the 60-hp pump shall be used to dewater the mine workings to <br /> JUNE 2021 25 AMENDMENT 6 <br />