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. Cher1'1 Creek Dam. The sum of the cost ot constructing the enlarged Cherry Creek spillway and the separable cost of the reregui.ating storage in TollGate Creek reservoir is estimated at about $33 million. All benefits to be achieved by. such an investment are essentially of an intangible nature due to the remote probability assigned to the occurrence of the Cherry Creek spillway design flood. (f) Intrabasin storage. Four general concepts utilizing storage within the Cher~ Creek basin were developed and analyzed as potential solutions to the problems created by the deficiencies in the Cherry Creek project. The basic features of these concepts, or plans, are raising Cherry Creek Dam in conjunc- tion with acquiring flood-threatened areas, modifying the location and size of the Cherry Creek spillway, raising Cher~ Creek DIiIIIl' and spillway crests, and providing rE:mote supplementary storage. These potential solutions are described in the following para- graphs and discussed in more detail in appendix V. (g) Plan 1. This plan would consist of raising the Cherry Creek Dam to prevent overtopping, acquiring additional lands in thE: Cherry Creek Reservoir, and acquiring flood pronE: lands along Toll Gate and Sand Creeks. A 5-foot concrete parapet would be cOnstructed along the crest of the dam, and all reser- voir lands and improvements below the muimum pool elevation, 5645 feet, would be acquired. The lands and improvements along Toll Gate and Sand Creeks which are subject to flooding from Cherry Creek Reservoir spillway releases would also be acquired. The total cost of this plan is estimated at $103 million. In addi- tion to the high costs, this plan has obvious social and pOlitical drawbacks associated with the real estate acquisition aspects. (h) Plan 2. The essential feature of this plan is an enlarged Cherry Creek Reservoir emergency spillway relocated to discharge into Cherry Creek instead of Toll Gate Creek. The concrete-lined spillw~ would be deSigned to discharge the probable maximum flood .and would be located in the right abutment of the dam. The spillway would consist of an ogee-crested weir, a 260-foot wide chute,and a stilling basin. Two multiple-lane bridges would be required to car~ the future interstate highway 225 over the spillWay channel. Operation of the spillway would limit the maximum pool level in Cher~ Creek Reservoir to eleva- tion 5630 feet and all reservoir lands below this elevation would be acquired to prevent potential property damage within the reservoir area. This plan to reroute the Cherry Creek project. spillway is estimated to cost about $16 million and may be an . 26 .