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1 <br />' The decline in piezometric levels in bedrock zones "upper sandstone facies", °siltstone/coal facies', <br />and "lower sandstone facies" was anticipated as probable impacts as the result of underground <br />' mining activities. As projected these impacts are localized and will most probably continue in the <br />proximity of the mined area. <br />As projected, subsidence in Red Wash initially resulted in water ponding in the stream bottom. The <br />high content of silt and clay carried by Red Wash rapidly fills the ponds. The silt and clay layers <br />have sealed any cracks that formed in the alluvium as the result of subsidence. Water continues <br />to flow in the surface channel at Red Wash while piezometric levels in the basal alluvial gravel have <br />dropped indicating that the basal alluvium is not recharged by surface flow infiltration. <br />3.3 Slgnlflcance of Impacts to Use of Water <br />The current rate of withdrawal of water from the lagoon in the White River alluvium is far below that <br />projected at full production. Based on the current level of production and the current rate of <br />withdrawal, Western Fuels is not likely to exceed the projected withdrawal rates even at higher <br />production levels. <br />' During this reporting period, lowering of the piezometric level in the 'upper sandstone facies' (at <br />TW2-7U, 2-7U, 35-4U, a 36-2U and 2-17U), the 'middle siltstone/coal facies° (at 2-7M and <br />TW2-17M) and the 'lower sandstone facies' (at 2-17L, TW2-7L, 2-7L, 4-20L, 36-2L, and 35-4L) <br />was noted. The significance of these impacts are minimal as no beneficial use of the bedrock <br />ground water exists in the Deserado Mine area. <br />' Water ponding in Red Wash as the result of subsidence over longwall panels No. 1, No. 2, No. 3, <br />No. 4 and No. 5 acted as stilling basins for deposition of clays and silts being carried down Red <br />Wash. The significance of this impact is beneficial as the sediment load to the White River was <br />reduced. The same impact is expected as a result of subsidence over subsequent longwall panels. <br />' 3.4 Ettectlveness of Mltlgatlon Measures <br />Mitigation measures at the Deserado Mine primarily include impoundment structures to control runoff <br />from surface sites and coal refuse piles. These structures have worked well as no discharges of <br />' runoff and possibly contaminated water from these impoundments have occurred. Reclamation of <br />areas disturbed during construction and operation is effective in controlling both erosion and <br />suspended solids during runoff events. Sediment control structures such as berms, ponds and <br />' sediment fences are used to control run off from disturbed areas until vegetation and the natural <br />contours are reestablished. <br />t <br /> <br />16 <br /> <br />