PERMFILE118274 - Laserfiche WebLink

Home Browse Search

West Elk Mine • affected. However, because there aze no rockfall areas in the South of Divide mining azea with an estimated verv high rockfall potential, longwall mining in this area will not affect the rock fall potential. Signs stating "Watch for Falling Rock" will be posted in strategic places along more well- traveled roads, such as the roads along Minnesota Creek, Dry Fork and Lick Creek at least one month prior to longwall mining and remain in place until approximately 18 months after mining and initial subsidence is complete in the azea. This procedure would be similaz to signs posted along such major interstate highways as I-70 in the Glenwood Canyon azea, where the rockfall potential and risk to travelers is high to very high compared to very low to risk to travelers in the South of Divide mining area). Importance of Baseline Landslide and Rockfal[ Data The most significant landslide in the South of Divide mining area, in terms of proximity to man- made structures, is located above the northern part of longwall panel E9 (Exhibit 60B, Map 1). Although there is a lazge landslide within the area of mining influence of the southeast corner of longwall panel E8 (mostly in the NE'/< of Section 8), the landslides located north and south of Minnesota Reservoir are the most important in the mining azea. It is important to monitor the existing, natural (baseline) conditions before mining begins in order to document their natural state. The cracks, bulges, and depressions observed in the landslide areas north and south of Minnesota Reservoir are much more extensive and dramatic than those caused by subsidence. The July 2004 aerial photographs obtained by MCC provides good baseline images of the • natural, pre-mining features in the South of Divide mining azea. Observations made by Mr. Dunrud in the West Elk mining azea indicate that mining may accelerate the natural landslide process, where there aze landslides that have already become unstable. However, annual observations of the surface cracks and depressions in the landslide area on Jumbo Mountain above mined longwall panels 8 and 9 determined that landslides aze very likely only related to natural mass-gravity movements and not related to mining. Baseline information has been gathered in the eight areas with low to moderate rockfall potential that aze listed above prior to any mining activities. Evidence of naturally-occumng rockfalls-such as remnant boulders at the base of steep slopes, or in the run-out zones of these areas with a rockfall potential will be documented prior to mining. Effects Of Subsidence And Mine-Induced Seismic Activity On Man Made Structures And Renewable Resources Man-made structures and renewable resources in the South of Divide mining azea basically consist of 1) A dam and reservoir (Monument Dam -Minnesota Reservoir), 2) stock watering ponds, 3) streams (primarily Dry Fork and the upper part of Lick Creek), 4) roads, and 5) local cabins. Minnesota Reservoir, the ponds, and the Deep Creek Ditch diversion to Dry Fork serve the dual purpose of being both man-made structures and containment structures for the valuable water resources in the azea. Based on annual subsidence observations in the Jumbo Mountain, Apache Rocks, and Box Canyon mining azeas during the last nine years, the following information is • considered appropriate for the South of Divide mining azea. 2.05-149 Revised June 1005 PRl0, Rev. March 2006; May 2006 PRl0