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Approximately half of the groundwater wells located within a one -mile radius of the <br />permit boundary are completed in alluvium at depths less than 66 feet. No impacts to water level <br />or water quality are expected to occur in alluvial wells. Bedrock wells within the one -mile <br />radius have completion depths varying from 30 to 750 feet bgs. Only the Armstrong well is <br />predicted to have 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 water are expected to <br />be similar to those currently observed (i.e., an average increase of about 40 mg /1 TDS <br />downstream from the mine). Water quality in the mined coal seams in the permit area is <br />expected to be impacted by the mining operation. Impacts to water quality will include an <br />increase in TDS, mainly in the form of sodium and bicarbonate. Background TDS <br />concentrations in the Allen and Apache coal seams are estimated to be about 435 mg /L and <br />1,105 mg/L respectively based on the electrical conductivity (EC) of groundwater from <br />monitoring wells NE -1 -10 (623 µS /cm— Allen) and NE -6 -10 (1,106 µS /cm— Apache) and the <br />assumption that TDS is equal to about 70% of EC. Observed TDS in the sealed portion of the <br />New Elk Mine has averaged 1,628 mg/L. After mining, the TDS concentration of groundwater <br />in the Apache and Allen coal seams near the underground workings is expected to be similar to <br />water in the sealed mine. <br />Water Consumption. Water is required in the underground mine for dust control in the <br />mining sections, along roadways and on the conveyor belt line. Water is consumed on the <br />surface in the preparation plant, bathhouse and surface roadways. Water is sourced from the <br />mine inflow and the Purgatoire River. Water consumption is dependent on production rates and <br />employment levels. <br />The preparation plant uses a closed- circuit design to recover and re -use water in the <br />benefaction process. However, some moisture is lost both to the clean coal and refuse. The <br />preparation plant has the potential to <br />TR56 2.05 -59 Revised 5/2011 <br />