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• sandstones soon fills the open cavity. There will be no active collapse and caving more than 30-40 <br />feet above the top of the seam. Following the initial caving the strata will deflect slowly with only <br />minimal fracturing (Section III of this permit and Schulte, 1957). <br />The effects of subsidence on Scullion Gulch and Red Wash are expected to be extremely short lived. <br />These ephemeral streams flow only during rapid snowmelt runoff or after heavy thunderstorms. Both <br />drainages carry high loads of bottom sediment and total suspended solids during flow events (see <br />Section II.C.2.c and II.C.2.d). Depressions in the stream bottoms as the result of longwall mining act <br />as sediment traps and quickly fill to return the stream to its natural gradient. Monitoring of Red Wash <br />and Scullion Gulch as described in Sections III.A.7.1 will allow detection of depressions which may be <br />repaired as described in Section III.A.7.j. See the Annual Hydrology Reports for the most current <br />information regarding the observations of these drainages. <br />When mining progresses within the distance at which subsidence effects to these ponds may occur, <br />visual inspections will be conducted (see Sections II.C.2.e, III.A.7.1 and III.A.7.j). If the inspections show <br />that the water holding ability of these ponds is diminished as a result of subsidence, the ponds will <br />either be repaired or replaced with a new pond in an area not affected by mining. If necessary, water <br />will be hauled in as a temporary measure while the repair or construction is being completed and <br />water is again stored in the pond. See the Annual Hydrology Reports for the most current information <br />regarding the observations of these ponds. <br />Refuse disposal effects on surface and groundwater systems is also expected to be minimal. Surface <br />runoff from the refuse banks will be quite small due to the relatively low precipitation (and yield) in the <br />• area. A sediment control pond is located downstream from each refuse disposal sub-area to keep <br />sediment from the refuse banks out of the streambeds. These ponds are monitored to determine the <br />quality of each discharge from the ponds. Seeps and springs are absent in the refuse disposal area. <br />Very little precipitation percolates down to the groundwater system in the area because of the low <br />precipitation and the tight sandstone and shale formations underlying the refuse banks. The area <br />contributes only a small amount of water to the surface or subsurface hydrologic system. <br />Currently the prep plant thickener water is discharged in the D-Seam workings. The disposal of the <br />prep plant thickener water in the D-seam workings will have no surface consequences. BME does not <br />believe there will be a need to discharge this water in the future. In case such a need arises, a <br />submersible pump will be lowered into the existing well SDH #2 and water will be discharged into the <br />existing settling ponds to allow sediments to settle before discharging the clear water. It should be <br />noted that in the past this water was pumped to the process pond PP-1 and then to PP-2 before its <br />final discharge. The discharged water had met NPDES quality standards for discharge. <br />In summary, the impact of mining on the quantity of surface water in the area will be minimal, primarily <br />because of the small withdrawal rates relative to the flow of the White River. As tension cracks <br />created by longwall mining will not penetrate very deep and will be filled by fine silt and clay increased <br />percolation of stream flow is not expected. Sediment production rates will increase locally during <br />construction activities but the yield from the area will be reduced due to the use of sediment control <br />devices. Subsidence from <br />• Midterm Review 2002 (Rev. 8/02) II.C-83 <br />