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:, <br /> <br />Mr. Michael 5. Savage Page Three <br />June 28, 1985 <br />4. The Division feels that the first ephemeral drainage above the <br />mine will be subsided after mining. It is thought that this <br />subsidence will cause inflows into the mine during spring runoff, <br />and that the dischar ed water will be of oor ualit The <br />app icant needs to iscuss mitigation o t is pro em, either by <br />treatment of the water upon discharge, or by creating a <br />Response: As shown on the Mine Plan Map (Map 11) presented in <br />the Peerless permit application, the main underground mine entry <br />will proceed in a direction generally parallel to Coal Gulch. A <br />series of panels will be driven from the entry system. Barrier <br />pillars will be established in the area between the mining blocks <br />for years 3 and 5, and 4 and 6 directly below the ephemeral <br />drainage. <br />In order to address Division concerns, Peerless does not plan to <br />extract pillars adjacent to main entries of the mine. As a <br />result, the barrier pillar between the mine main entry and the <br />panels will remain in place following mining. In addition, in <br />those areas where cover is less than 300 feet, Peerless will not <br />pull pillars. By leaving pillars in an area beneath the <br />ephemeral drainage and providing barrier pillars along the main <br />entry and between mining blocks, Peerless does not anticipate any <br />subsidence problems which could effect the ephemeral drainage. <br />If water is encountered in the mine, whether due to subsidence or <br />natural infiltration, Peerless will route all such water to an <br />underground sump for use during mining activities as explained in <br />the permit application and subsequent responses to Division <br />concerns. Any water discharged from the mine workings will be <br />routed to the sedimentation pond and will be subject to NPDES <br />discharge effluent limitations. <br />If treatment of this water is required, treatment procedures will <br />be as described in the response to comment number 2, set forth <br />above. <br />5. The Division may propose that no pillars be extracted in areas <br />with less than 300 feet of overburden to prevent subsidence in <br />ephemeral drainages. The applicant may wish to address this <br />relative to mine inf ow and Door duality discharge. <br />Response: At this time, Peerless will commit to no pillar <br />extraction in areas with less than 300 feet of overburden. This <br />should effectively prevent subsidence in the ephemeral drainages <br />found within the permit area. Peerless will also establish a <br />subsidence monitoring program in order to monitor subsidence in <br />the area. <br />