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COLORADO LEGACY LAND <br /> 12150 E.Briarwood Ave.Suite#135,Centennial,CO 80112 <br /> T.(303)862-3928 RECEIVED <br /> March 31,2021 APR U 12021 <br /> Ms.Amy Eschberger DIVISION OF RECL4WTION <br /> Colorado Division of Reclamation,Mining,and Safety MINING AND SAFETY <br /> Department of Natural Resources <br /> 1313 Sherman Street,Room 215 <br /> Denver,CO 80203 <br /> Subject: Fourth Quarter 2020 Sampling Results, <br /> Schwartzwalder Mine,Golden Colorado, <br /> Mine Land Reclamation Permit No.M-1977-300. <br /> Dear Ms.Eschberger: <br /> The fourth quarter sampling event at the Schwartzwalder Mine was conducted by Ensero Solutions US, Inc. <br /> (Ensero) field staff on November 09 to November 12, 2020. In addition to presenting sample data, CLL is <br /> including a cross-section schematic to illustrate the Schwartzwalder mine pool elevation with respect to the <br /> elevation of the Ralston Creek surface water sample locations. During the fourth quarter sampling event,Ralston <br /> Creek was dry within the permit boundary;three samples were collected from offsite locations in seasonally low- <br /> flow conditions. As shown in the attached schematic,given that the elevation of surface water location ARH(SW- <br /> ARH)was 88.6 feet above the elevation of the mine pool at the time of sampling,the concentrations of uranium <br /> in Ralston Creek outside of the permit boundary at SW-ARH and downstream locations SW-LLHG and SW-WEIR <br /> are not tied to the mine pool. In addition, the elevated water level in Monitoring Well 15 (MW-15) shows a <br /> groundwater divide exists between the mine pool and Ralston Creek at SW-ARH. <br /> • Surface Water Data: There are thirteen quarterly surface water (SW) sampling locations. Figure 1 <br /> shows the location of each surface water sample locations along Ralston Creek. Table 2a summarizes <br /> surface water field parameters. Table 2b summarizes the analytical data results. The analytical <br /> laboratory data report and the chain of custody are attached to this report.A copy of the electronic data <br /> deliverable(EDD)excel file for these samples are included in this submittal. <br /> • Groundwater Data: There are thirteen quarterly groundwater monitoring well (MW)locations.Table <br /> 1 shows the monitoring well elevations. Figure 2 shows the location of each MW.Table 3a summarizes <br /> groundwater field parameters. Table 3b summarizes the analytical data results. The analytical <br /> laboratory data report and the chain of custody are attached to this report.A copy of the EDD excel file <br /> for these samples are included in this submittal. <br /> • Mine Pool Elevations:Table 4 summarizes the mine pool elevations for the quarter.Pumping of the <br /> mine pool has consistently maintained the mine pool elevation below the regulatory limit of 150 feet <br /> (ft)below the Steve Level even during months of no pumping.Maintaining the mine pool below the <br /> regulatory limit has established a hydraulic gradient away from Ralston Creek,preventing mine water <br /> from entering the creek in the permit area. <br /> If you have any questions regarding this letter,please do not hesitate to contact me. <br /> PAGE 1 OF 15 <br />