2013-11-27_PERMIT FILE - C1981018A (2)

Home Browse Search

Subsidence predictions were conservative and actual measured subsidence was always less than predicted. Depth increases as the mine progresses to the north. As depth increases, subsidence decreases. As acknowledged by DMG and OSM, subsidence of archaeological sites over LW -2 was found to cause no significant impacts. The lease COC -51551 sites were predicted to subside less than that over LW -2 and therefore are not expected to be significantly impacted. However, longwall mining under these sites did not occur since this area became inaccessible when part of the D Seam was sealed due to the fire. III.A.8 Mine Ventilation A permanent fan is installed at the D -Portal ventilation slope. This fan operates in a blowing configuration pushing fresh air into the mine from the Ventilation Entries and through the working area. It operates continuously with the exception of scheduled maintenance periods. MSHA approved the detailed plans for the ventilation of the underground working. Three ventilation shafts were constructed in the B -Mains to exhaust return air. Details of the construction are given on Maps 151, 155 and 156. The first raise bore shaft is 210 -feet deep and 12 -feet inside diameter, the second intended to be 965 -feet deep and 14 -feet inside diameter but failed, and the third 813 -feet deep and 7 -feet diameter. The shaft openings are fenced off and elevated to control unauthorized access to MSHA standards. The shaft sites are approximately 100'x200'. Light use roads about 2410 and 1200 feet long were constructed from the existing haul road to B -Vent Shafts 1 and 3. A 1400 foot long light use road extension from RDH -3 services B -Vent Shaft 2. Later, a 2150 foot light -use road was constructed connecting RDH -3, SH -1, SH -2, and B -Vent Shaft 2 to the haul road. Return shafts are constructed to the B -Seam to exhaust return air. RS -1 and RS -2 are 300 and 308 feet deep, steel lined and five -foot diameter. RS -3 is steel lined, six -feet in diameter, and 310 feet deep. The upper and lower 20 feet of the annulus between the steel liner and the shafts are grout sealed with concrete. The middle zones of the annulus are gravel filled with weep holes drilled in the liner to allow drainage. RS -4, RS -5, RS -6, and RS -11 L are steel lined, two -foot in diameter (RS -11 L is 26" ID), 585, 610, 600, and 615 -feet deep with the annulus grouted the full length. RS -4 was assisted by an adjacent 11" open borehole. A 3 -foot diameter, 362 -foot deep ventilation shaft was drilled to the West Mains in the D -Seam. Map 153 shows the details of RS -1 which are typical of the other return shafts and roads. Locations and light -use roads to these shafts are shown on Map 147. During early 1987, gassy conditions were encountered at the Deserado Mine. To relieve those conditions, BME drilled a 12 -1/4 inch hole (LW1 -1) and six (6) 10 -5/8 inch holes (LW1 -2 to LW1 -7) into the gob created behind the protective shield of the longwall 1. In September, 1988, a vent hole (LW1 -8) was drilled to relieve methane gas in the sealed area of the longwall panel #1 to improve ventilation in other working areas of the mine. In January 1990, an additional ten (10) Minor Revision #158 (11/2013) III -2 6