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2.05 APPLICATION FOR PE[affT FOR 8[TRF~CE OR D2IDII~ODID MINING AGTIVI'.FLFS -- <br />MINIM[A~1 R}7QLT1REMalPB F'OR OPERATION AND RF7CI~R'IO2i PLANB. <br />• 2.05.6 Mitigation of blirface Coal Operation Mining Eaq~acts. (COnt'd.) <br />(6) (e) (i) (B) (Cont'd.) <br />of alternating claystone, sandstone, arri minor coal seams. <br />Geologic faulting may modify the subsidence profile Over <br />extracted panels. Due to the c®~etent nature of the Overburden <br />Stratd, topographic lnflllences Wlll be minimal 12'1 dY3W aigle <br />variations. Specific rack mechanic and subsidence processes are <br />described in the Subsidence Study, Volume 3. <br />(6) (e) (i) (C) <br />General experience gained from undergrotiuxi mining suggests a <br />relationship between Overburden thickness, immediate roof <br />lithology and extraction ratio, to subsidence manifestations <br />upon the surface. In irLStances Where minimal outcrop barrier, <br />massive sandstone roof, and less than 800 ft. Overburden exists, <br />experience has shown that tension cracks may migrate to the <br />surface. Orchard Valley Mine's water supply pipeline and <br />F electrical power line has been undermined and demonstrates that <br />development mining does not affect or interrupt such structures. <br />Typically, hydrology features such as ponds, springs, or <br />streams, have not been undermined, so information is yet to be <br />• gathered. Site specific mining experience concerning subsidence <br />~ is submitted in the "Annual Hydrology and Subsidence <br />Report." That information has been incorporated into the Geo- <br />Hydro Consulting, Inc. report. Refer to the Subsidence <br />Appendix, Volume 3. For additional information, refer to <br />Colorado Westmoreland roc's "Annual Hydrology and Subsidence <br />Reports" which are submitted annually to the Division. <br />MR 92-80 Revised 2/11/92 <br />152 <br />