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The FIRM shows Cherry Creek "Zone A" (no base flood elevations determined) 100-yeaz <br />flood limits confined to the east of Castlewood Canyon Road. The indicated floodplain <br />would therefore not affect the UBSR property nor the actual mining area itself. <br />No other drainage planning studies or master plans are known to affect or impact the <br />subject property. <br /> 2. Major basin drainage characteristics. Willow Creek near the project site is a sandy <br /> ephemeral drainage, conveying snow melt and runoff flows from primarily undeveloped <br /> areas. There are approximately 1,840 acres tributary to the design point where the <br />' proposed mine access road will cross Willow Creek. <br /> 3. Irrigation facilities. There are no existing irrigation facilities on-site, nor will the project <br /> build any irrigation facilities. <br />' 4. Soil classification map. Figure B shows the approximate location of the mining site on <br />the SCS soil base map. <br /> <br /> B. Sub-Basin Description <br /> 1. Historic drainage. The current topography of the proposed mining area generally slopes <br /> 2% to 3% to the northeast. <br /> Nine sub-basins were delineated within the proposed mining area. These basins range in <br /> area from 33 acres to 186 acres (see Appendix A, Pre- and Post-Mining maps). The <br /> crushed stone quarry contains sub-basins one through six. Drainage from the crushed <br /> stone upland sub-basins is to the northeast. The cut stone quarry contains four basins <br /> (seven through nine). <br /> To delineate the sub-basin the Castle Rock South 7.5 Minute Series Quadrangle map <br />' produced by the United States Geologic Survey (USGS) was used. The USGS's 20-foot <br /> contour intervals were interpolated to five feet within the mining area and the Willow <br />' Creek access road crossing (see 24" x 36" Drainage Study Pre-Mining Basins maps). <br /> 2. OfJ-site drainage. Drainage from the upland mesa areas is captured by a series of steep, <br /> V-shaped drainages cut into the rhyolite deposit and the underlying Dawson Formation. <br /> The drainageways below the crushed stone quarry drain into Cherry Creek northeast of <br /> the site. The drainageways below the cut stone quarry drain north to northwest into <br /> Willow Creek. <br /> <br />1 <br />r <br /> <br />