PERMFILE103730 - Laserfiche WebLink

Home Browse Search

West ElkMrne Roads will be monitored six months before they aze within the angle of draw and on a weekly basis while they are within the angle of draw. After the roads aze outside the angle of draw, monitoring will continue on a monthly basis for six months. All road monitoring is dependant upon accessibility. Buildings Subsidence effects on buildings have not been observed in the Apache Rocks and Box Canyon mining areas. Baseline information on buildings, such as foundations, walls, chimneys, and roofs, has already been obtained prior to any mining on the Dry Fork Cow Camp in July 2004. Pre- mising information is planned on all buildings prior to mining. Impacts Beneath the Mined Coal Seam Based on mapping and observations by Mr. Dunrud in the B Seam of the Somerset Mine, impacts to the coal and rocks below the mined coal bed are expected to be limited to about one mining thickness. There is no expected mining impact to the underlying D Seam coal because its top commonly occurs at least a mining thickness below the based of the E Seam. Furthermore, impacts to the floors of the mine workings aze expected to be limited to the chain pillars, because the floors of the longwall panels are loaded with caved roof rocks and overlying strata before deformation in the floor can occur. Floor heaving, pillar punching (the pillar punches into the floor and roof rocks), and squeezing (plastic flowage, see Dunrud 1976 for more details) are the only expected deformation in the immediate mine floor, which consists of impure coal, shale, sandstone and claystone. Deformation in the floors of the chain pillars is expected to occur after the longwall panel is mined and the pillazs begin to yield. Possible Subsidence Consequences Apache Rocks and Box Canyon Mining Areas -The greatest surface impacts are expected to occur along the precipitous slopes and cliffs that flank West Flatiron and in the steep canyon slopes of the Box Canyon mining area (Box Canyon, Sylvester Gulch tributaries to the east, and the unnamed drainage to the west of Box Canyon). Though unlikely, the worst possible consequences foreseen are that: Cracks as much as 50 to 100 feet deep may develop above the chain pillars common to the first three northern panels and may divert intemuttent flow in Box Canyon and the unnamed canyon to the west of Box Canyon to the mine through local fractures or to permeable rocks in the overburden (see Map 14 for details). Flow, in this unlikely event, would likely be through lineaz zones of structural weakness (i.e., fractures, joints) which may have caused the canyon to form initially. It is believed, however, that fractures and joints will terminate in the soft, ductile shale and claystone units. • 2.05-141 Revised November 2004 PR/0