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0 2.05.6(6) <br />calculated factor of safety of 2.5 directly under the creek. To assure long <br />term stability, a pillar must have a factor of safety of 1.5 or greater. No <br />backstowing or backfilling of voids will be performed. The minimum pillar <br />factor of safety exceeds 1.4 near the rock storage area for the worst <br />assumed coal strength and load transfer conditions. Because this panel is <br />only needed for the short term, and will soon be backfilled to the top by waste <br />rock, subsidence is not expected for assumed continuous (nonfaulted; <br />Brinton 2009) strata conditions. <br />A limited extraction zone was established along the bleeder entries in the <br />vicinity of Freeman Gulch and the vent shaft in Freeman Gulch to assure <br />ancient land slides were not reactivated by subsidence. <br />Mining in low overburden areas adjacent to the possible fault trace is <br />explained in section (f)(ii)(B) above. <br />A limited extraction zone will not be established along Stevens Gulch per <br />• Federal Coal lease #37210 stipluations in order to protect Steven's Gulch <br />Road from the impacts of subsidence since the overburden in this area is <br />approximately 1500 feet. <br />(f)(iii)(C) <br />The Operator will protect its facilities from rockfall by constructing one berm <br />at the location shown of Map 15 -2 and in accordance with the design <br />presented in Volume VII, Tab 11. No other protection measures are <br />proposed. <br />Subsidence monitoring stations are not proposed to determine when the <br />potential for rockfalls might diminish. The Operator will assume rockfall <br />hazard continues for two years after an outcrop is affected by mining. <br />(f)(iv) A detailed description of the measures to be taken to mitigate the effects of <br />any material damage or diminution of value or foreseeable use of lands which <br />may occur. <br />46 PR -12 2.05-152- 02/10 <br />PPR6V 6D <br />IOt.flo <br />