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u <br />BME intends to abide by all State and Federal regulations to reduce possible subsidence. Any <br />damage to the surface grazing land, such as tension cracks, will immediately be filled in if found to be a <br />safety hazard to livestock. If a large number of major cracks are found to exist in a close area, BME <br />will enclose this particular area with a fence until the initial effect of subsidence has passed and the <br />cracks have started to close. <br />Underground mining will not be conducted beneath or adjacent to any perennial stream or <br />impoundment having a storage volume of 20 acre-feet or more. Stockponds and reservoirs <br />undergoing active subsidence will be monitored and measures will taken to prevent sudden outflows of <br />water from them. <br />III.A.7.j Red Wash and Scullion Gulch. Red Wash and Scullion Gulch are ephemeral stream beds <br />which flow only in periods of snowmelt and heavy 2infall. Red Wash traverses from north to south <br />across the eastern edge of the permit area. Scullion Gulch traverses from northwest to southeast <br />across the permit area. Parts of these drainages are expected to subside and tension fractures are <br />expected to open in the crust. <br />Due to the nature of subsidence over a longwall system the disturbance to the hydrological flow in and <br />• below the drainages is expected to be minimal. Subsidence occurs in a wave action following the <br />longwall face. The extent of horizontal reaction in front of the longwall face is dependent on the angle <br />of draw. As the longwall passes, cracks will open as the ground is placed in tension and then close as <br />the stress wave proceeds beyond any given location. It is generally believed that any cracks that <br />develop in the crust will be discontinuous. <br />It was not considered possible for water to flow from the surface and enter the mine area. There was <br />600-1,200 feet of overburden above the coal seam in the Red Wash area. When the coal is extracted <br />the roof caves immediately behind the longwall. The swell of the shales and sandstones is expected to <br />soon fill the open cavity. It is expected that there will be no active collapse and caving more than <br />300 feet above the top of the seam. Following the initial violent caving of the immediate roof, the <br />overlying strata deflects slowly with only minimal fracturing. <br />Examination of the one known roof fall in the abandoned Staley-Gordon Mine showed that the fall <br />ceased propagating upwards about 16 feet above the roof line. The caving stopped when a unit of <br />massive, strong sandstone was reached. This roof fall occurred more than ten years ago, and an <br />examination (March 1981) showed that it was still stable and had not propagated any further into the <br />overburden. <br />• Permit Renewal #3 (Rev, 8/99) III-20 <br />