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For areas around the shops, stockpiles and other frequently used areas where <br />additional sediment control is necessary, runoff will be controlled using diversion <br />ditches and filters. The ditches will normally have triangular cross sections and will <br />divert runoff through filters. <br />4.6.2 ALLUVIAL VALLEY FLOOR ANALYSIS <br />This discussion relies upon The environmental resources information described in <br />Section 2. These descriptions are based upon both field investigations and review and <br />analysis of infrared aerial photographs of the area. <br />4.6.2.1 Alluvial Valley Floor Studies <br />Mapping of Unconsolidated Stream Laid Deposits <br />The unconsolidated stream laid deposits within the vicinity of the mine are <br />shown on Exhibits 2.5-21 and 2.5-22. Except the modern flood plain (Ott) most of the <br />terraces are on the west side of Trout Creek. There are a few isolated terroces in <br />the northern part of the Moffat Area within The permit boundary. Terraces Qt2 and <br />0t3 are mantled by material interpreted as slopew ash and coiluvium and are not <br />connected to the Otl terrace. The older Otq terrace is more subdued and <br />discontinuous than the younger terraces. No evidence of groundwater was found in the <br />Ot3 and Otq terrace alluvium (Section 2.5.2.5) while the Qt2 terrace contains a <br />perched aquifer recharged by snowmelt, rainfall and irrigation flows. Flow is towards <br />a line of springs on the east face of the terrace. The Otl terroce is connected to <br />Trout Creek. <br />On Oak Creek, the Otl terroce has been used for both highway and railroad <br />right-of-way. One higher terrace, Ott, was mapped on the east side of Oak Creek <br />about 20 feet higher than the Otl terrace. This terrace is veneered by four to six <br />feet of colluvium and shows no indication of significant groundwater (Section 2.5.2.5). <br />Mapping of Flood Irrigated Lands <br />Exhibit 4.6-16 shows the irrigation ditches and irrigated lands in the vicinity of <br />the Edna Mine. The irrigation ditches were plotted using USGS topographic maps, as <br />well as aerial photographs. The irrigated lands were determined in the vegetation <br />Revised 10-81 4.6-59 <br />