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<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 roofline. 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 />Expert hydrological consultants were asked to predict the effect of subsidence on the Red Wash and <br />Scullion Gulch drainage areas. It was generally agreed that there will be some temporary disturbance <br />to the hydrological flows of the drainages. The sedimentary rock overlying the coal is tight and free of <br />faults and fractures. (See the Hydrological and Geology Sections of this application). <br />Tension cracks were predicted to form in the crust and in the secondary layer in the creek bottom. <br />However, the thick layer of fine silt present in the drainage systems is predicted to hide and quickly <br />seal off any openings. The effect of subsidence on the groundwater under Scullion Gulch is unknown <br />but will likely mimic that which occurred in Red Wash. <br />BME monitored Red Wash during active subsidence. The schedule for monitoring Red Wash was tied <br />to monitoring nine alluvial wells established in Red Wash. When the longwall face advanced to within <br />200 feet of the Red Wash alluvium, tension cracks that might appear on the surface were searched for <br />• on a schedule of once every two weeks. This schedule continued until the longwall face advanced <br />past the alluvium 400 feet. After the longwall advanced more than 400 feet past the Red Wash <br />alluvium, surface crack monitoring resumed at a schedule of once every two months to coincide with <br />monitoring of the nine alluvial wells. No interruption in the flow of water to the White River occurred, <br />although a tractor was available to smooth out any localized subsidence and ensure an uninterrupted <br />flow of water. A further discussion of the Red Wash monitoring study is found in the Hydrology <br />Section. <br />When longwall retreat mining on Panel LW-16 commenced beneath Scullion Gulch, the surface was <br />visually monitored at least twice per week. Equipment was available for repair work but was not <br />needed. Some cracking was observed but most promptly sealed as the longwall advanced. Several <br />small cracks remain on the north side of Raven Park dam but appear to be well above the high water <br />mark. No problems are anticipated due to this cracking. Repairs will be made in the future if <br />warranted. <br />There will be no mining beneath any known aquifer that serves as a significant source of water supply <br />to any public water systems and there will be no mining beneath any public buildings, urbanized areas <br />or towns. <br />• Midterm Review (8/2002) III-2 0 <br />