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conservative one due to the construction of Chatfield, Cherry Creek and Bear Creek flood control dams. Using stilling basin design techniques as. set forth in the Bureau of Reclamation's book "Hydraulic Design of Stilling Basins" the resulting basin for Q = 29,000 cfs with a drop of 3' in elevation is found to be a modified type IV basin. The modification involves removing the chute blocks and was done because of the low Froude number (2.4) of the flow and to simplify construction. The stilling basin is to be 145' wide for a unit q of 200 cfs/ft. A sill was used at the downstream end of the stilling basin to shorten the length of basin required and to lessen the erosion downstream in the event of a flood flow. This lessening of erosion is necessary due to the highly erodible nature of the site soil as discussed in the Geology section of this report. The proposed dam will, with flash boards in, provide the same water surface elevation as the existing dam and thus assure a diversion of at least 200 cfs down the side river channel. In the event of a major flood the stop logs and supports would wash out and the dam would then not impede flow in any way. In such an event a flow of 44,000 cfs could be handled by the main channel without overtopping the river banks upstream of the dam. The side river channel would increase this even more. Some minor erosion damage would occur but the dam should not be affected by this flow. The proposed dam will not change the sedimentation process from that of the existing dam. The construction materials consist of concrete and steel sheet piling. Both are readily available in the Platteville area. The river will be diverted away from the dam site by building a large earth embankment upstream of the site which will divert the river flow down the side channel to the west of the site. Materials for this embankment will be taken from a large sand bar immediately upstream of the dam site. -19-