2016-02-03_PERMIT FILE - C1981038A

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42.05 APPLICATION FOR PERMIT FOR SURFACE OR UNDERGROUND MINING ACTIOITIES -- MINIMUM REQUIREMENTS FOR OPERATION AND RECLAMATION PLANS. 2.05.6 Mitigation of Surface Coal Mining Operation Impacts. (Cont'd.) (3) (b) (iv) (Cont'd.) be impacted by coal mine subsidence. Springs issuing from colluvial debris are not expected to be impacted above 800 ft, of overburden for the following reasons: Subsidence induced tension cracks propagating through a maximum of 600 and 850 ft, were ob- served at the Somerset and Orchard Valley Mines (Dunrud, 1976 and CWI, 1982, respective- ly). These features were typically located on overlying slopes near coal outcrop conditions where total extraction was accomplished. Dun- rud (1984) presents a discussion and summa- rizes the cracks were "apparently caused can- tilever-type (block rotation) failure". Establishment of Guidelines for Mining Near Surface and Underground Bodies of Water Bah- lock and Hooker, 1977) states: "Any single seam of coal beneath or in the vicinity of any body of surface water may be totally extract- ed, whether by long wall mining or by pillar robbing, provided that for each 1 f.t. thick- ness of coal seam to be extracted a minimum of 60 ft. of solid strata cover exists between the proposed working and the bed of the body of surface water." The maximum probable extraction thickness of the "D" coal seam within the permit area is 10 ft. Employing the above recommendations for total extraction, the safe overburden thick- ness for the Orchard Valley Ptine would equal 600 ft. The recommendations presented for partial ex- traction beneath a body of surface water are as follows: "1. No entry should be driven in any coal seam lying beneath or in the vicinity of any body of surface water where the total • Added 12/26/84 Added 03/07/85 Revised 10/01/87 128