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Probable Hydrologic Consequences New Elk Mine 28 <br />• No hydrologic impacts or only temporary minor changes in water level are expected to occur in the <br />continuous zone. No flow or water quality impacts are expected to occur to surface water including springs <br />and seep from mining in the Allen and Apache seams. Mine dewatering will draw current water levels <br />down in Allen and Apache seams by 200 or more feet in the permit area. Water level data from packer <br />testing indicate that steep vertical gradients currently exist in the strata adjacent to coal seams. The steep <br />gradients are related to mine dewatering and /or CBM production and suggest that there is limited potential <br />for propagation of drawdown across bedding. Approximately half of the groundwater wells located within <br />a one -mile radius of the permit boundary are completed in alluvium at depths less than 66 feet. No impacts <br />to water level 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. Some of these wells could potentially <br />experience reductions in water levels during mining if they are screened in strata near the Allen or Apache <br />seams. Most of the wells, however, are located outside of the area that will be undemined and are screened <br />several hundred feet above the mined beds. Water quality impacts to the Purgatoire River and the alluvial <br />aquifer from surface operations are expected to be similar to those currently observed from the mine (Le an <br />average increase of about 40 mg /1 TDS in river water downstream from the mine, and 400 to 500 mg /1 TDS <br />increase over background in alluvium downgradient of the RDA). <br />• <br />4164A.110130 Whetstone Associates <br />PR 02 Exhibit 8(4) Page 149 Revised 1/31/11 <br />