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ALLUVIAL VALLEY FLOOR DETERMINATION <br />MCCLANE CANYON MINE <br />COAL MINE WASTE PILE <br />GARFIELD COUNTY, COLORADO <br />Geology <br />The bedrock geology of the investigation area consists of Cretaceous Mount Garfield <br />Formation Sego Sandstone members of the Mesaverde Group. The Mount Garfield <br />Formation consists of buff and gray fine- to medium -grained sandstone, and gray shale <br />and thick coal sequences in the lower portion of the formation. The Sego Sandstone <br />consists of buff and light gray fine-grained sandstone and gray shale. <br />The various surficial deposits identified in the investigation area are generally <br />composed of debris from the local bedrock units. However, some clasts within the <br />alluvium are likely from other bedrock units located farther upstream. The surficial <br />deposits identified during the 2009 site visits include alluvium of East Salt Creek, <br />landslide deposits, debris fans from tributaries to East Salt Creek, and colluvium. Based <br />on stratigraphic position, it is assumed the landslide deposit is the youngest because it <br />overlies all other units, including the older alluvium located adjacent to the active <br />channel. The active incised channel of East Salt Creek contains alluvium which is <br />younger than the landslide deposit. <br />East Salt Creek Alluvium <br />Sediments in the active channel consist of clay to boulder -sized material. Generally, <br />the active stream channel consists of sands and gravels with areas of cobbles to boulders, <br />although the boulder -sized material is mostly limited to an area downstream of the former <br />agricultural diversion (this will be discussed in more detail later in the report). Some of <br />the bank areas are composed of fine sand to clay. The creek is incised about 15 to 20 feet <br />into older alluvium and, as a result, numerous vertical exposures of alluvium are <br />observed along the creek (Photos 7 and 8). The older alluvium consists of well -sorted <br />fine- to medium -grained sand with thin silty sand and pebble conglomerate layers. The <br />pebble layers are up to 4 inches thick and pinch in and out over distances of 6 to 10 feet. <br />A basal gravel or conglomerate layer was observed in the exposed alluvium wall at the <br />level of the current active channel. The basal gravel consisted of rounded cobbles to 2 to <br />4 inches in diameter, with some clasts up to 10 inches. A soil profile of up to 18 inches <br />was observed at the top of the alluvium. <br />fR0 <br />Resources <br />Corporation <br />