2012-05-30_PERMIT FILE - C1981012A (2)

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Monitoring of impacts during mining and previous studies of probable hydrologic consequences (WWL, 1980 and Greystone, 1994) indicate that underground inflows and mine dewatering have little or no communication with surface water. This conclusion is consistent with the subsidence analysis and conceptual model for the New Elk Mine. The maximum extent of subsidence fracturing with increased vertical transmissivity is projected to extend 195 feet above the top of the highest mined coal. The minimum thickness of overburden between the Apache seam and drainage bottoms is 450 feet. A zone of continuous deformation will be present from about 195 feet above the coal to 50 feet below ground surface. No hydrologic impacts or only temporary minor changes in water level are expected to occur in the continuous zone. No flow or water quality impacts are expected to occur to surface water including springs and seep from mining in the Allen and Apache seams. Mine dewatering will draw current water levels down in Allen and Apache seams by 200 or more feet in the permit area. Water level data from packer testing indicate that steep vertical gradients currently exist in the strata adjacent to coal seams. The steep gradients are related to mine dewatering and/or CBM production and suggest that there is limited potential for propagation of drawdown across bedding. Approximately half of the groundwater wells located within a one -mile radius of the permit boundary are completed in alluvium at depths less than 66 feet. No impacts to water level or water quality are expected to occur in alluvial wells. Bedrock wells within the one -mile radius have completion depths varying from 30 to 750 feet bgs. Some of these wells could potentially experience reductions in water levels during mining if they are screened in strata near the Allen or Apache seams. Most of the wells, however, are located outside of the area that will be undermined and are screened several hundred feet above the mined beds. Water quality impacts to the Purgatoire River and the alluvial aquifer from surface operations are expected to be similar to those currently observed from the mine (i.e. an average increase of about 40 mg/l TDS in river water downstream from the mine, and 400 to 500 mg/l TDS increase over background in alluvium down gradient of the RDA). Water Rights. The rights of users of surface and ground water present in the area of the New Elk Mine are reviewed in Section 2.04 of this application. No significant amounts of groundwater were encountered in this area. Therefore, the New Elk Mine's effect on groundwater users is not expected to be significant. Also, projections have been conducted which show insignificant effects on downstream surface water quality and quantity beneficial uses. Water Monitoring Program. A monthly surface and groundwater monitoring program was initiated in February 1984 to gather baseline and operational hydrologic data to assess potential effects of mining. This program was based on stipulations placed on the permit and has been revised multiple times in the interim period. Requirements of the monitoring program are contained in Table 27, Hydrologic Monitoring Requirements and Table 28, Water Quality Parameter Sample Suites. TR -56 2.05 -90a Revised 1/31/11