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than just alluvium, and hence the term valley fill was chosen. This nomenclature <br />is consistent with the DSGS mapping of the area (Madole, 1989). <br />Where possible, fan deposits were mapped based on the geometry of these geomorphic <br />features as observed on aerial photographs and field inspections. Fans are <br />deposited in this general area at the mouths of intermittent tributary streams. <br />Colluvium was mapped where these deposits appeared to be more than five feet thick <br />and it was clear that the principal mechanism of transport was gravitational. <br />Landslide deposits were mapped where there was geomorphic evidence of slope <br />failure and the resulting deposits were present. This term encompasses a broad <br />variety of slope Failure types, including debris flows, slumps and earth flows. <br />Dry Creek is an intermittent stream that contains sediment that is only <br />infrequently in transport. Sediment from the valley slopes has built up and has <br />yet to be removed. Former floodplains are stranded on the order of five to 15 <br />feet above the current stream channel bottoms. This channel incision is probably <br />in part related to major flooding that occurred as recently as 1985. However, <br />even this flooding failed to remove a significant portion of the sediment stored <br />in the channel. As the floodplain re-establishes its equilibrium these incised <br />channels will be widened. <br />Downstream of the Dzy Creek canyon mouth, the valley opens up into a broad <br />alluvial floodplain, This broad floodplain valley is located south (upstream) of <br />the Loadout facility area in portions of Sections 22, 23, 27 and 28 (see Exhibit <br />9-2, Pre-mining Topography). Upland benches and slightly sloping hillsides abut <br />the floodplain terraces. Dry Creek has historically meandered across the <br />floodplain in response to sediment deposits and flood flows, However, in recent <br />times, Dry Creek has been channelized in Section 28, and possibly Section 22. Dry <br />Creek is incised by five to 10 Feet; the channel walla are near vertical and the <br />maximum widths are typically less than 20 feet. The Dry Creek (and Stokes Gulch <br />immediately upgradient of the confluence with Dry Creek) channel terraces are <br />naturally sub-irrigated; the floodplain terraces are flood irrigated. <br />As Dry Creek moves through permit area (rail loop) the valley Floor narrows - Dry <br />Creek becomes sinuous and incised. A narrow channel terrace is aubirrigated. The <br />vegetation consists of sedge meadows and willow shrublands. The floodplain <br />terraces and slightly sloping benches are too high on the landscape to be <br />TR-07 19-3.2 Revised 03/06 <br />