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JD -7 Mine — Drainage Design Plan 21 <br />Figure 6. Photograph Showing Pit Diversion West <br />The remaining sub - basins on the escarpment route water naturally, without man -made diversion structures. <br />These sub - basins are labeled N -A, N -B, N -C, N -H, N -I, N -J, and N -K in Figure 3 and they convey non - <br />contact stormwater runoff to the valley floor from the steep slopes of the Monogram Mesa escarpment. <br />Sub - basins N -K and N -J are located in the western portion of the project area, and receive and route <br />stormwater runoff from the crest of Monogram Mesa to the valley floor adjacent to the topsoil stockpile <br />(Figure 3). Stormwater in sub -basin N -K that arrives at the valley floor enters a braided ephemeral channel <br />that passes west of the topsoil stockpile (Figure 7). As shown by the ephemeral channels on the digital <br />orthophoto image (USGS, 2011), stormwater that reaches the valley floor from sub -basin N -K may <br />infiltrate or flow northward across the valley floor to receiving sub - basins D -15 and D -14. <br />Stormwater from the 116.08 acre sub -basin N -J is delivered to a well - developed alluvial fan in sub -basin <br />D -14 (Figure 7). Alluvial fans are natural energy dissipation structures that allow sediment deposition and <br />infiltration recharge along mountain fronts. The soil stockpile is constructed downslope of the alluvial fan <br />and is constructed to a height of 6 to 8 feet above the natural ground surface. Most of the stormwater from <br />sub -basin N -J infiltrates along the alluvial fan as velocities slow and the channel becomes diffuse. <br />4149A.130926 Whetstone Associates • <br />