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Mr_ Dave~Maxwell - 2 - July 20, 198 • F-seam Mine Plan Changes The F-seam mine plan has peen mdaifled slightly as follows: a small area, three (3) panels, will oe mined immediately inside and to the west of the F-seam portals. This area underlies a portion of the approved UDDer Waste Pile, wn~cn is yet not guilt. WECC also plans to cease mining in the lWbS panel due to decreasing coal thicKness, An additional panel (1W3N) may oe developed north of and paralleling the 1 west Suoma~ns, if geological conditions allow. This panel replaces a parallel set of small panels previously proposed in this Same portion of the mine plan. Tne suosidence implications of one larger panel should be less disruptive than the higner flexure resulting from repetitive oarriers remaining after the extraction of the group of smaller panels. WECC is planning to discontinue easterly advance of the 1st East Submain, oecause of odd roof conditions adjoining Sylvester Gulch. The alternative is to advance a new set of East Submain Entries to the east southeast, and then drive a series of nine (9) panels (IEIN through lE9N) to the east northeast. Waste Disposal A lower waste rocx pile was permitted in 198c to handle 1,771,924 tons of • waste over a 15.7 year Reriod, through the year 2000. At the time of permitting, WECC projected that the mine would produce approximately 110,000 tons of waste per year. Construction of the two ramps and ventilation shaft for the 8-seam will produce 54,000 tons of waste. This, coupled with an estimate of 50,000 tons of waste associated with the 1989 mining of the F-seam, will maintain the projected refuse production rate. Underground development waste ~s projected at 105,000 tons in 1990, 50,000 tons each in 1991 and 1492 and 75,000 tons per year thereafter, resulting in storage in the tower waste pile through 2003. The ramp material is compasea of alternating sandstone and shales. It has a neutral DH, low salinity and a low iron content; SARs average 12.74. Recommended quality standards for selenium range from 0,1-2 mg/k; the ramp material averages 0.09 mg/k, at the lower end of the range. The material to be generated oy slope and shaft development in the B-seam is of higner shear strength than the material currently contributed to the pile as a result of F-seav mining, so staoility of the pl~e will not oe affected. Suos~dence Monitoring and Control Within the angle of draw of the B-seam mine plan area there are no renewadle resource lands, structures or geological hazards that require Rrotection or mitigation from suos~dence. The predicted extent of suositlence to result from the F-seam was approximately four (4) feet. The extent of subsidence noted during the past five years has peen less than two (2) feet. The predicted • extent of subsidence to result from mining in the 8-seam is four (4) feet for room and plliar mining in ootn the B and F seams. If the B-seam is mines using longwall methods, the predicted cumulative subsidence could reach ten (10) feet.