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2.05.6(6) <br />The permit area has been segregated into three zones of expected <br />subsidence impact. The zone of greatest subsidence impact is in areas <br />where the overburden is between 110 and 500 feet. The zone of <br />intermediate subsidence impact is in areas where the overburden is between <br />500 and 1,000 feet. The zone of minor subsidence impact is in areas where <br />the overburden is over 1,000 feet. Map 27, Subsidence, presents the <br />locations of these three zones. The discussion in Volume IIIA, Exhibit 15 <br />Subsidence concludes that under normal conditions, subsidence cracks do <br />not appear likely to propagate through more than 500 feet of overburden. <br />Overburden thicknesses over 800 feet have been classified as having a <br />negligible risk of surface fracturing developing. This is a conservative upper <br />limit under normal conditions. <br />A table at the end of this section presents a listing of springs ponds and <br />water rights. The table presents the elevation of each feature and the <br />estimated depth each lies above the coal seam to be mined. Generally no <br />subsidence protection will be provided for springs unless they are a decreed <br />water right and only then if the spring has an overburden depth of less than <br />800 feet. Most of the springs and ponds within the permit boundary and <br />adjacent area have overburden depths which exceed 800 feet. <br />A limited extraction zone as referenced below is defined as an area in which, <br />if mined, will be limited to first mining only with no pillar slabbing. The <br />proposed location of the limited extraction zones are presented on Map 27, <br />Subsidence and Maps 14 & 1413, Mine Plans. <br />Pond P -1 is located in a zone of greatest subsidence impact. For this <br />reason, this pond will be protected by a limited extraction zone. The limited <br />extraction zone is defined by extending a safety zone a distance of fifty feet <br />around the pond and then projecting a line down at the angle of draw until it <br />intersects the coal seams. <br />Pond P -2 is located in a zone of intermediate subsidence, however the <br />overburden below P -2 is nearly 1,000 feet. For all practicable purposes P -2 <br />is in a zone of minor subsidence. Therefore, no limited extraction zone will <br />be provided for Pond P -2. <br />PR -12 2.05-147- 02/10 <br />/� pPkov6p <br />!t /IL /fa <br />