PERMFILE60488 - Laserfiche WebLink

Home Browse Search

Subsidence predictions have been approached from a conservative standpoint and actual measured subsidence has always been less than predicted. Depth increases as the mine progresses to the north and as depth increases, subsidence is decreased. As acknowledged by DMG and OSM, subsidence of archaeological sites over LW-2 was found to not cause significant impacts. The sites in lease COC-51551 were predicted to undergo less subsidence than the sites 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 24 hours per day, 365 days per year, with the exception of scheduled maintenance periods. MSHA has approved the detailed plans for the ventilation of the underground working. A ventilation shaft was constructed in the B Seam to exhaust return air. Details of the shaft construction are given on Map 151. The raised bored shaft is about 210 feet deep and 12-feet in inside diameter. The shaft opening is fenced off and elevated to control unauthorized access to MSHA standards. The shaft site is approximately 100'x200'. Alight use road about 2410 feet long was constructed from the existing mine haul road to the shaft site (see • Map 151). In anticipation of possible future power requirements for the area, approximately 3400 feet of overhead electric utility lines may be installed. See Map 151. Return shafts RS-1 and RS-2 were constructed to the B-Seam to allow return air to exhaust. RS-1 is about 300 feet deep and RS-2 is about 308 feet deep. Both RS-1 and RS-2 steel lined to a five foot finished diameter. RS-3 will have a finished diameter of six feet when lined with steel and will be about 310 feet deep. The upper and lower 20 feet of the annulus between the steel liner and the shafts are grout sealed in with concrete. The middle zones of the annulus' are gravel filled with weep holes drilled in the liner to allow drainage. Alight duly access road, approximately 8500 feet long, was constructed to RS-1 and RS-2. RS-3 will require 1550 feet of light use road. A a- 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 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) 10-5/8 inch holes (LW2-1 to LW2-8, LW2-4B and LW2-68) were drilled in the longwall #2 and • Midterm Review (8/2002) III-26