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SCCC Response: Please refer to Map 2.05.2-Mi, Life of Mine Plan Map, Map 2.05.3-M2 <br />Mine Plan Map Operation Timing, and Exhibit 2.05.6-E1 for information to address this rule. <br />Future mining may move into the western portions of the PSCM permit area but can not be <br />detailed at this time due to unknowns of coal quality, underground mining conditions, and the <br />market. Any future mining in this area will be in full compliance of all federal and regulatory <br />requirements and Division approved permit revisions for the PSCM. <br />47. The next to the last paragraph on page 2.05-3 says: "No longwall mining is projected for <br />the initial permit term; therefore, no subsidence is anticipated." Consistent with this <br />statement, subsequent sections of the permit application relating to hydrologic impacts <br />(2.05.6(3)) and subsidence impacts (2.05.6(6)) do not address potential subsidence <br />impacts. Rule 2.05.6(6)(b) requires the application to include a description of the worst <br />possible consequences which subsidence, if it occurred, could have for structures and <br />renewable resource lands. This Rule presumes that subsidence will occur and does not <br />eliminate the need for predicting the worst possible consequences from subsidence in a <br />case where subsidence appears unlikely. Although the application proposes only advance <br />room-and-pillar mining that may result in subcritical panel widths, subsidence can occur <br />in this type of operation due to a variety causes, for example: pillar failure, floor heave, <br />rock bursts in the workings, intersection of unexpected faults in the workings, and <br />unexpected sudden inflows of water or gas into the workings. Pillar failure can be <br />promoted over a long period of time by fluctuating water levels in the workings that <br />weaken pillars. Please address potential subsidence impacts as required by Rule <br />2.05.6(6). <br />SCCC Response: SCCC has addressed the potential worst case subsidence impacts as required <br />by Rule 2.05.6(6) on pages 2.05.6-99 and 2.05.6-99.1 of the revised PSCM PAP. SCCC <br />identified a 1264 acre area of potential worst case subsidence (see page 2.03.18). In addressing <br />these impacts SCCC contracted with SubTerra, Inc., which has extensive experience in <br />subsidence impact and predictions at Twentymile Coal Company, to complete a subsidence <br />evaluation. This subsidence evaluation is presented in new Exhibit 2.05.6-E1. Also used as <br />resources are the documents shown in new Exhibits 2.05.6-E2 and 2.05.6-E3, What is Mine <br />Subsidence? and Illustrated Effects of Mine Subsidence. All revised or new PAP materials are <br />included in the PAP revision package. <br />SubTerra's evaluation includes the worst possible consequences from pillar failure, floor heave, <br />rock bursts, and the intersection of faults and sudden inflows of water or gas. This evaluation <br />confirms that no subsidence is expected with the development of main entries and continuous <br />miner sections with low extraction ratios. <br />In the process of evaluating the worst possible consequences, SCCC has identified all structures <br />and renewable resource lands above the proposed mine development areas. Three of the <br />identified structure/renewable resource lands occur where mining is in excess of 600 feet, and no <br />subsidence impacts are predicted. Little Grassy Creek and a 69 KV powerline are near the portal <br />entrance where mining depths are 200 to 400 feet. The subsidence evaluation recognizes that the <br />impacts of subsidence can be greater at shallow depths and is supported by the document What is <br />Mine Subsidence? This document, by the Pennsylvania Department of Environmental <br />Protection, states that Pennsylvania "will not authorize underground mining beneath structures <br />where the depth of overburden is less than 100 feet (30.5m), unless the subsidence control plan <br />13