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Vegetation did not successfully become established at the Mine 5 Fan outslope. It is <br />theorized that this site is subject to surface scow as a result of the downhill movement of <br />snow during the winter. Movement of the snow pack has not been measured, however, it <br />was noted that following the 2005 snowmelt, virtually no evidence of the constructed <br />benches remained. Further, little to no germination was observed over the majority of the <br />slope. These observations suggest that the swface of the slope was subjected to a <br />scouring action which tends to smooth the outslope surface, either removing or burying <br />the benches and seed. <br />Discussion <br />The outslopes at Coal Basin were created dwing construction of the benches used to <br />support underground mining operations. These structures are composed primarily of <br />coarse to fine grained shale, sandstone, carbonaceous shale and coal particles. Debris and <br />mining related plastic and metallic materials aze interspersed with the sediment. It is <br />presumed that the slopes were created by pushing excavated materials over the side of <br />pre-existing slopes to facilitate the development of the mines. The unconsolidated <br />outslope materials rest near the angle of repose neaz their crest, with the slope becoming <br />gentler near the toe of each. The slopes are typically very long, up to 800 feet in length, <br />and vary from one to about five acres in size. Excepting the Mine 3 South outslope, each <br />outslope is uninterrupted by a topographic break. An abandoned mine haul road <br />intersects the Mine 3 South slope, effectively segregating it into two distinct featwes. <br />The outslopes generated a lazge volume of sediment as a result of both direct <br />precipitation and from upland water draining off the overlying mine benches. The great <br />degree of active gully development at each of the slopes was ample evidence of the <br />volume of sediment generation that was attributable to each of the slopes. For years, the <br />sediment from the outslopes was allowed to report directly to Coal and Dutch Creeks, or <br />their tributaries. The 1999 data summary in Table 3 gives a relative indication of the <br />volume of sediment that were available for delivery from the outslopes to receiving <br />streams. <br />Coal Creek has been identified as an impaired stream as a result of excessive iron <br />content. The Division has theorized that the marine origin of many of the Coal Basin <br />sediments is responsible for the elevated iron concentrations. As a result, an elevated <br />iron content was not an unexpected occurrence. However, it was also postulated that the <br />volume of iron -beazing sediment being generated from the outslopes wuld be a <br />contributing factor to the impairment designation. Therefore, it was reasoned that <br />stabilization of the mine bench outslopes could result in a measurable decrease of iron in <br />the receiving streams. <br />Stabilization of the slopes could be achieved either by physically altering the slopes <br />through earth moving operations, or through revegetation efforts. Removal of the slopes <br />was not a viable option, so in-situ stabilization through vegetative processes was selected <br />as the most likely avenue of reducing sediment contribution from these facilities. The <br />13 <br />