2013-02-06_REVISION - C1991078 (6)

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been operated and reclaimed so as to protect the hydrologic balance in the permit and adjacent areas. No hydrologic impacts were observed during the bond release inspection. Potential groundwater and surface water impacts of the operation have been assessed and monitored over the course of the operational life of the mine. An adequate soil loss demonstration was incorporated into the permit document in 2009 and was evaluated with the Phase 11 bond release conducted in June 2010. Based on our review of site conditions and available monitoring data the Division concludes the following. Groundwater Impacts The Hamilton Mine site itself is virtually dry with no shallow groundwater present and there is seldom enough runoff to fill stock ponds. Bedrock groundwater is deep at depths of approximately 120 feet below ground surface. The only significant groundwater in the permit area occurs in sandstones of the lower Burro Canyon Formation. The Operator has installed 3 monitoring wells, designated BW -1, BW -2, and BW -3, in this aquifer. Alluvial groundwater is nonexistent in the permit area. Alluvial groundwater along Naturita Creek was monitored in four wells installed by the applicant AW -4 through AW -7 but these are located nearly one mile from the permit boundary. Three additional alluvial wells AW -1 through AW -3 were installed within the permit area but were dry throughout the monitoring period. Typical well completion information and monitoring locations are provided on Map 110 in the PAP. The Operator collected baseline water level and quality data and continued to sample all wells in accordance with the approved plan until 1998. In July of 1999 the Division approved a revision to halt surface and groundwater monitoring until two years prior to a Phase III bond release request. However, the monitoring plan was subsequently modified through MM -12 and the Operator committed to reinitiating the surface and groundwater monitoring for one year prior to this Phase III bond release. In conjunction with the re- commencement of the approved surface and ground water monitoring, the Operator performed a spoil spring survey following snowmelt this past spring. The supplemental surface and ground water monitoring data submittal was received by the Division on October 5, 2012 and reviewed for this final Phase III assessment. Bedrock groundwater occurs 90 to 100 feet below the lowest mineable coal seam. Several strata of impermeable shale separated the aquifer and the mined coal seam. Given this, it was predicted the mining operation would not have any effects on the aquifer. The monitoring data submitted by the Operator and received by the Division on October 5, 2012 confirm that no impacts to the aquifer have occurred. The aquifer discharges to various springs adjacent to the permit area. The Operator monitored several area springs; SP -1 Long Draw Spring, SP -2 Section 33 Spring, SP -3 Homestead Spring, Bramiers Draw Spring, SP -5 East Homestead Spring and SP -6 B &W Spring No. 1. These springs are generally dry, and have not been impacted by the mining operation. Spoil spring development was a possible hydrologic consequence of mining at the site. A study conducted by the Division dated July 14, 1999 discusses the development of a spoil spring and the potential consequences in detail. According to the Division's assessment, spoil spring development was most likely to occur in or next to the drainage in the northwest quarter of Section 33. During the May 2012 bond release inspection the perimeter of the mine area was walked including the likely area for spoil spring development and spoil springs were not observed. Toes of all slopes throughout the permit area were inspected and no evidence of spoil spring development was found as a result of Page 13 of 16