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hillside above the waste pile, will also be collected and routed through the ponds. Nearly all <br />of the runoff from this area will be channeled into the west pond. Only the runoff from the <br />small yazd storage area below the offices will be routed to the east pond. The pond hydrology <br />and design is discussed below. <br />Reach 6 is a small open channel which intercepts runoff from the small natural area west <br />of the mine and diverts via a culvert, reach 9, to the main yard drainage ditch reach 8. Reach <br />8 leads directly to the West Pond. Reach 10 is a small ditch which intercept runoff from an <br />undisturbed area above the waste pile and routes it around the pile and down into the yard. <br />Reaches 7 and 11 are pipe within the yard and reach 12 is a Swale which crosses the main <br />entrances road and moves drainage water to the East Pond from the lower yard area. <br />3. Drainage Basin Characteristics <br />3.1 Basin Geometry and Soils <br />The drainage basin is divided into three parts, the undisturbed eastside, the undisturbed <br />westside and the yard area. These areas were delineated using the U.S. Geological Survey's <br />(USGS) Kline and Hesperus 7~lx" topographic maps. Figure 3 shows the basins delineated on <br />these maps. The East and West Basins are further divided into areas on steep hillslopes and those <br />on the top of the plateau. The mine surface drainage map, C-4, was used in delineating and <br />determining the hillslope areas, the yard and the two small areas adjacent to the yard. <br />The measured areas for each sub-basin and composite basins are shown in the table below. <br />Basin length and average slope were also measured from the topographic maps, see table. <br />There are three soil types represented throughout the basin. These boundaries were <br />delineated on Figure 3 using information obtained from the Soil Survey of Ia Plata County <br />Area, Colorado, Soil Conservation Service, USDA. The most prominent type is I.azear-Rock <br />outcrop complex (SCS unit JJ42) which occurs on the steeper hillslopes at the edges of mesas. <br />This unit covers 6396 of the basin and is about 50% Iazeaz very stony loam and 30% Rock <br />outcrop. It is shallow and well drained and is given a hydrologic group rating of D. <br />Approximately 2896 of the basin is covered by Plome fine sandy loam (SCS unit X55). This deep <br />well drained soils if found on the top of the mesa. It is a hydrologic group B. The last soil found <br />in this basin, 946 of azea, is Witt loam. This is also a deep, well drained soil with a hydrologic <br />group B and is found on the mesa top. <br />The following table summarize the geometric and hydrologic characteristics associated with <br />each drainage basin. <br />~, <br />2 <br />June 1995 <br />