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• Expert hydrological consultants were asked to predict the effect of subsidence on the Red Wash and Scullion Gulch drainage areas. It was generally agreed that there will be some temporary disturbance to the hydrological flows of the drainages. The sedimentary rock overlying the coal is tight and free of faults and fractures. (See the Hydrological and Geology Sections of this application). Tension cracks were predicted to form in the crust and in the secondary layer in the creek bottom. However, the thick layer of fine silt present in the drainage systems is predicted to hide and quickly seal off any openings. The effect of subsidence on the groundwater under the Red Wash and Scullion Gulch is unpredictable and purely speculative. BME has monitored Red Wash during active subsidence. The schedule for monitoring Red Wash is tied to monitoring nine alluvial wells established in Red Wash. When the longwall face advanced to within 200 feet of the Red Wash alluvium, tension cracks that might appear on the surface were searched for on a schedule of once every two weeks. This schedule continued until the longwall face advanced past the alluvium 400 feet. After the longwall advanced more than 400 feet past the Red Wash alluvium, surface crack monitoring resumed at a schedule of once every iwo months to coincide with monitoring of the nine alluvial wells. No interruption in the flow of water to the White River occurred, although a tractor was available to smooth out any localized subsidence and ensure an uninterrupted flow of water. A further discussion of the Red Wash monitoring study is found in the • Hydrology Section. When longwall retreat mining on Panel LW-1 B commences beneath Scullion Gulch, the surface will be visually monitored at least twice per week. More frequent monitroing may be required by DMG if problems arise. Inspections will be documented and any surface subsidence features will be described and photographed. Observations and photographs are to be included in the annual report. The monitoring will continue until retreat has proceeded a distance from the channel equal to at least the depth of the seam. Equipment will be available for repair work. Subsidence caused reversals of gradient or cracking will be repaired if necessary following consultation and concurrence with the BLM and US Army Corps of Engineers. There will be no mining beneath any known aquifer that serves as a significant source of water supply to any public water systems and there will be no mining beneath any public buildings, urbanized areas or towns. III.A.7.k Subsidence Effects on the Powerline. A need to re-orient the mine plan impacted the initially proposed non-subsidence corridor. Either considerable longwall tonnage would be eliminated or the concept of anon-subsidence corridor had to be abandoned. To ensure that maximum economic recovery of the coal is achieved, BME chose the latter alternative. Permit Renewal #3 (Rev, 8199) III-21