2012-06-20_PERMIT FILE - C2010089 (87)

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retention and protection in the small, entrenched drainage. Plate 10 shows a small ephemeral drainage channel lying between Deer and Coal Creeks, northeast of Decker, Montana, and east of the Decker West mine. The rocky material surrounding the flume is principally of clinker (l.e., baked sh and fused coal ash),,the principal surficial material at this location. The and we rete- tively vigorous vegetative growth during the drier months and is as an alluvial valley floor up to the terrace partially visible he ._. ..,� a .. o people (see arrow). Plate 11 is taken nearby at Deer Cr butery of the Tongue River, which alao contains an alluvial valley o ern limit of which is indicated by the arrow. The vegetation of this a ncipally grasses and is heavily used by stock. ' Plate 12 is a view of Little Youngs Creek, a tributary to the Tongue River in Wyoming near the Wyoming- Montana border. Pere overburden stripping and storage has begun to encroach on the alluvial valley floor (see Table 2). The alluvial valley floor is about 100 meters wide in this area. Plate 13 shows the Tongue River near Kleenburn, Wyoming, north of Sheridan. The terrace levels are evident along the distant aide of the river. Coal and clinker outcrops rim the valley. The alluvial valley floor is fairly broad at this location (see arrows). Plates 14, 15, and 16 provide views of some of the tributary streams in north- western Wyoming. Plate 14 shows Little Rawhide Creek, a tributary to the Little Powder River north of Gillette, Wyoming. This area is within the alluvial valley floor which is approximately 50 meters wide at the location shown. The minor ter- races in the alluvial valley floor area (see arrow) are included. Plate 15 shows Cabello Creek, a tributary to the Belle Fourche River in north- eastern Wyoming, an upstream view toward the northeast. The alluvial valley floor is approximately 200 meters wide along the original (natural) channel. The width varies with the entrance of tributaries. The water impoundment* is a result of the mining operation. Strippable coal extends under this valley. A number of terraces are evident in the background (see arrows) and delineate the alluvial valley floor. Plate 16 was taken in the Little Thunder Basin area at the gauging station installed on Little Thunder Creek. This intermittent *channel has not been mapped as an alluvial valley floor though certainly the impounded run -off water (perched on silt and /or bedrock) is of value to stock and wildlife. Plates 17 and 1B were taken in northwestern Colorado. Plate 17 shows a reach of the Yampa River Sixteen Kilometers west of Craig, Colorado, where the alluvial valley floor is quite broad, The nearest coal mining activity is presently six kilo- meters east. While this particular area has not been thoroughly investigated, the alluvial valley appears to extend to the low bluffs in the middle of the photograph (see arrows). Plate 18 is a view along Fish Creek located southwest of Steamboat Springs, Colorado, where spoiled overburden has been placed in the drainage channel. The alluvial valley floor at this point was 150 meters wide. The original stream channel has been filled and the man -made channel along the left of the photograph was in the process of being moved farther to the right at the time of the photograph. A railroad embankment rims the right side of the alluvial valley floor (see arrow). * Impoundments created by post -wining grading may be beneficial if the impoundment, and the impounded water are safe and suitable for their intended use. Unfortunately, the incorrect assumption is often made that all impoundments are good for the semi- arid West. High evaporation rates which concentrate salts in the impoundments and leaching of spoils will cause. some impounded water to be unfit for continual use. Impoundments constructed npgradient of spoils and intercepting ground water have a much greater likelihood of containing water suitable for agricultural and wildlife uses than do surface water impoundments and other impoundments intercepting water that has passed through spoils.