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IJCEmEX RECEIVED <br /> Building a better future APR 2 9 2020 <br /> DIVISION OF RECLAMAriOIV <br /> April 28,2020 MININGAND Sgy <br /> \ins.Amy Eschberger Via FEDEX <br /> Division of Reclamation, Mining and Safety TRK#7702 5371 6025 <br /> Environmental Protection Specialist <br /> 1313 Sherman Street, Room 215 <br /> Denver,Colorado 80203 <br /> Re: CEM EX Lyons Mine Permit M-1977-208 <br /> Technical Revision No.12, Revised Groundwater Monitoring Plan <br /> First Quarter 2020 Monitoring Data <br /> Dear Ms. Eschberger: <br /> This letter transmits the surface water and groundwater data associated with the sampling of the cement kiln dust <br /> disposal area(C-Pit). This report includes data from the C-Pit ponded water and related groundwater monitoring for <br /> the first quarter of 2020,covering the reporting period from January 1,2020 to March 31,2020. Table 1 presents data <br /> for the last four quarters. <br /> Groundwater samples were collected on March 18,2020 from the CEM-ooi and CEM-oo4 groundwater monitoring wells <br /> and from the C-Pit ponded water. The inspection of groundwater monitoring well CEM-oo5 on March 18,2020 indicated <br /> that there was not enough water volume to collect a representative sample. <br /> The samples collected from C-Pit ponded water and the groundwater monitoring wells were analyzed for pH,chloride, <br /> sulfate,total dissolved solids,selenium,and thallium.The reported pH data are based on the pH analyses performed at <br /> the time of sample collection in the field(Table 1). The measured pH at groundwater monitoring well CEM-oo4 and <br /> analytical results for chloride,sulfate,total dissolved solids(TDS),selenium and thallium from the March 18,2020 <br /> groundwater sample were within the target levels prescribed by TR-12,as shown in Table 1. <br /> In addition,a Stiff Diagram of the groundwater cation/anion data from CEM-oo4 compared to the average and Both <br /> percentile of the cation/anion concentrations from the last four quarterly samples of C-Pit data is provided in Figure 1 <br /> for reference. As shown in Figure 1 and consistent with past reports,the signature for CEM-oo4 continues to be <br /> significantly different from that of C-Pit. <br /> LEGEND <br /> - C-Pit 90"'Percentile <br /> C-Pit Average <br /> ® CEM-004 from 3/18/2020 <br /> Calcium Bicarbonate <br /> (as CaCO3) <br /> Magnesium Carbonate <br /> Potassium Chloride <br /> Sodium Sulfate <br /> I I I I I I I I I <br /> 80 60 40 20 20 40 60 80(meq/L) <br /> Figure 1: First quarter 2020 cation/anion data for CEM-oo4 compared to C-Pit <br /> 1 <br />