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<br />A total of 11 cross sections were used to model the topography in the <br />~ 1150 feet reach near the site. Average cross section spacing was 115 feet; <br />the sections were taken closer together where flow conditions were critical. <br /> <br />Under existing conditions, the main channel would carry from 50 percent <br /> <br />to almost 95 percent of the 100-year discharge. Main channel velocities <br /> <br />range from 18.3 to 32.3 feet per second. Main channel flows are in the stable <br /> <br />supercritical flow range, with Froude numbers of approximately 2.0. <br /> <br />The left (east) overbank contained almost 45 percent of the total flow <br /> <br />near the heliport opposite the Water Treatment Plant site. Velocities were <br />14.2 feet per second. There were no other areas of left overbank flow. <br /> <br />,.~ <br />'. <br /> <br />The right (west) overbank contained almost 50 percent of the total flow <br />in the area of the existing ponds. Velocities were 8.5 to 10.5 feet per <br />second. Flow depths average about three feet. The right overbank is <br />constrained by the mine office road fill near station 43 + 20; shallow overbank <br />flows are forced back to the main channel upstream of this road. The right <br />overbank upstream and at the Water Treatment Plant Site may contain shallow <br />flows resulting from upstream bank overtopping. <br /> <br />The location of the 100 year flood plain under existing conditions is <br /> <br />shown in Figure 3. Flow characteristics at selected loctions are shown in <br /> <br />Table 1. A typical section is shown in Figure 5 and the water surface profile <br /> <br />in Figure 4. <br /> <br />~ <br /> <br />5-3 <br />