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7.0 SUBSIDENCE 'CONING <br />7.1 ZONES OF MINOR SUBSIDENCE Ih1PACT <br />Minor or no subsidence impact is expected in those <br />areas where there is a thick overburden cover. An overburden <br />thickness in excess of 1,600 feet has been selected to <br />define areas of low subsidence impact, as shown on Plate 17. <br />These areas are limited to the northern part of the proposed <br />long-term lease area, where the •3 round surface has risen <br />steeply above the northerly dipping D-seam. <br />The amount of subsidence arising from the mining of <br />individual panels will be relatively small, typically less <br />than about 1.5 feet. Maximum strains at surface resulting <br />from mining will generally be small. The development of <br />surface cracks due to subsidence is not anticipated. Damage <br />should therefore be limited to buildings or structures which <br />are particularly sensitive to settlements or strains. No <br />structures of this type are known to axis*_ within these <br />zones. <br />7.2 ZONES OF INTERMEDIATE SUBSIDE[CE II+IPACT <br />• Zones with between 800 and 1,600 feet of overburden <br />cover above the D-seam are designated as zones of <br />intermediate subsidence impact on Plate 17. Moderate <br />subsidence magnitudes and strains are predicted for these <br />zones. Appreciable damage may result to buildings or <br />structures due to subsidence. There is a risk that <br />subsidence fractures may occur at the ground surface where <br />the overburden within these zones is thinner and the <br />geological and mining conditions are unfavorable. These <br />zones cover most of the central portion of ttie proposed <br />long-term lease area. <br />Four structures which lie within this zone may be <br />susceptible to unacceptable damage from the subsidence and <br />strains which are expected under the current mining plan. <br />These are the following, which all lie within Stevens Gulch: <br />o htuckle House Restaurant <br />o Pitkin Mesa Pipeline <br />o CWI Stevens Gut .h well <br />pipeline <br />and hlorrell's ranch <br />field and associated water <br />These structures may squire special protection or <br />modification to enable them to adequately withstand the <br />affects of subsidence. Alternatively, modifications to the <br />u <br />~~ <br />- J- - <br />