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I I I I I I I I I I I I I I I I I I I foundation soils. A core trench of this nature is recommended for both dams; however, it is not a requirement for the East Dam. The core trench is not optional for the West Dam due to its known underseepage. A toe drain was considered for both dams and is highly recommended. A toe drain is a relatively inexpensive way to ensure stability of the downstream toe and it also satisfies the State Engineer's requirement that the seepage be controlled. From a purely analytical standpoint, a toe drain is not absolutely required for the East Dam as no seepage problems were detected by this study. For the West Dam; however, a toe drain is mandatory to control the seepage which is readily apparent at the dam toe. As stated previously, we do recommend a toe drain of some sort at both dams and believe the benefits will always outweigh the cost. The riprap design for the upstream slope consists of a twenty-four inch (24") layer of riprap with a nine-inch (9") layer of riprap bedding. The riprap sizing will range from eighteen inches (18") to three inches (3"), and the bedding from three inches (3") to sand size. If present costs of the rehabilitation become a problem, the thickness of the riprap layer could be reduced to 18 inches to reduce the cost. However, more long term maintenance can be expected if a thinner layer is utilized. 2. Outlet Works. The outlet works considered utilizing is a 36 inch reinforced concrete pipe to replace the existing 36 inch conduit. This size of outlet should be adequate to serve the downstream needs as it is presently doing. Due to the extreme length of the outlet (367 feet), it does not appear cost effective or needed to increase the size. The pipe will be bedded on concrete through the dam and on sand outside of the dam toe. The inlet will be a simple headwall arrangement, and the outlet end will include an energy dissipater and a Parshall flume to measure flows. The wetwell will be cast-in-place concrete with a control gate similar to the existing arrangement. A more sophisticated outlet works is not considered necessary for a dam this size with the storage capacity available. 3. Spillway. Two locations were studied for placement of the emergency spillway. The plan view drawing in Appendix H of this report shows the two proposed locations. Both locations have pluses and minuses associated with them due to structural consid- erations and downstream hindrances. The spillway located on the east side of the East Dam is the preferred location from a hydraulic standpoint and from a structural standpoint. This spillway is shorter and gets the flow into the natural drainage with less probability of a washout which could back water up again&t the dam toe. This spillway will require a large quantity of excavation and also will require the purchase of 6 to 8 acres Right-Of- Way across a private landowner. V-4