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-3- <br />• the mapped area. Structurally, the region is gently folded with the <br />Grand Hogback Monocline influencing bedding attitudes. A synclinal <br />axis associated with the fold is located about 2 miles to the west of <br />the site. 7l~e mine, located approximately 1/4 mile to the west of the <br />refuse site, is presently extracting coal from seasu in the lower <br />portions of the Mesa Verde group. Alluvial and colluvial deposits of <br />Holocene and Pleistocene age and man-placed fill forma thin veneer <br />over the underlying Manoos shale at various locations across the site. <br />Zhe approximate areal extent of these map units is shown on Figure. 1. <br />Following is a description of the units mapped: <br />1. Man-placed Fill: (Map Symbol-af) Several locations of man-placed <br />fill were observed at the site. Generally, the fill consists of spoils <br />associated with the coal mining operation. The fill is composed of <br />• low-grade coal, claystone, siltstone and sandstone. Recent fill in the <br />present refuse area is being placed under ao~ntmlled conditions. Older <br />fill, randomly dumped along the existing mad upslope of the mine is in <br />a very loose state. Tension cracks showing up to 4 ind~es of <br />horiwntal movener-t and 12 ind~s of vertical movement were observed at <br />the top of the southern pile. Coal particles buried in this pile have <br />ignited and are presently burning underground, as evidenced by smoke <br />emitting from several of the tension cracks. <br />2. Alluvium Associated with Present Drainages: (Map Symbol Qal) <br />Alluvial soils are present along the rorth edge of North Thonpson Creek <br />and in the tributary drainage below the present refuse pile. These <br />soils range in depth from 5 to 15 feet, and generally auisist of clay <br />~~ <br />