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73 <br />drawdown across bedding. No flow or water quality impacts are expected to <br />occur to surface water including springs and seeps due to mine dewatering. <br />Approximately half of the groundwater wells located within a one -mile radius <br />of the permit boundary are completed in alluvium at depths less than 66 feet. <br />No impacts to water level or water quality are expected to occur in alluvial <br />wells. Bedrock wells within the one -mile radius have completion depths <br />varying from 30 to 750 feet bgs. Only the Armstrong well is predicted to have <br />increased potential for impacts by mining. <br />Dewatering discharge from the mine will be treated before being released to the <br />Purgatoire River, and impacts to water quality in the river from discharged <br />water are expected to be similar to those currently observed (i.e., an average <br />increase of about 40 mg/1 TDS downstream from the mine). Water quality in <br />the mined coal seams in the permit area is expected to be impacted by the <br />mining operation. Impacts to water quality will include an increase in TDS, <br />mainly in the form of sodium and bicarbonate. Background TDS concentrations <br />in the Allen and Apache coal seams are estimated to be about 435 mg/L <br />and 1,105 mg/L respectively based on the electrical conductivity (EC) of <br />groundwater from monitoring wells NE -1-10 (623 uS/cm-Allen) and NE -6-10 <br />(1,106 uS/cm-Apache) and the assumption that TDS is equal to about 70% <br />of EC. Observed TDS in the sealed portion of the New Elk Mine has averaged <br />1,628 mg/L. After mining, the TDS concentration of groundwater in the <br />Apache and Allen coal seams near the underground workings is expected to be <br />similar to water in the sealed mine. <br />Water Consumption. Water is required in the underground mine for dust <br />control in the mining sections, along roadways and on the conveyor belt line. <br />Water is consumed on the surface in the preparation plant, bathhouse and <br />surface roadways. Water is sourced from the mine inflow and the Purgatoire <br />River. Water consumption is dependent on production rates and employment <br />levels. <br />The preparation plant uses a closed-circuit design to recover and re -use water in <br />the benefaction process. However, some moisture is lost both to the clean <br />coal and refuse. The preparation plant has the potential to process 650 raw <br />tons per hour for a maximum tonnage of 3.0 million raw tons of coal per year. <br />The Operator estimates that 11 gallons/raw ton for make-up water is required <br />in the processing, while utilizing 21.0 gallons/raw ton. In the event that all <br />of the additional make-up water is acquired from the river, the New Elk Mine <br />would consume 97 acre-feet annually. The recycling of thickener slurry <br />through the New Elk Mine workings will decrease the amount of water <br />consumed from the Middle Fork of the Purgatoire River. Updated well <br />permits are required to initiate recycling of slurry. The Operator is currently <br />working with the Division of Water Resources on the requirements to update the <br />slurry injection well permits. <br />Section 2.05 RN -6 10/17/2016 <br />