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1400 ac-ft 2800 ac-ft 4150 ac-ft 480 ac-ft 960 ac-ft 1450 ac-ft I -- I I I I I I I , r, I I I I I ..... I " I I I I deposits, or terrace deposits, whi.:h consist of cobbles, gravel and sand of basalt, occur on the higher divides west of Beaver Creek and to the north of the proposed damsite on either side of Beaver Creek. (See Figures IV-] and IV-a) Suitable material for cQnstruction of an earthfill or rollercrete dam can probably be developed from the colluvial deposits. The terrace deposits could be devel('ped as sources of gravel and sand for aggregate and f,n filter mater:lal. A large source of hsrd rock for rockfill dam is not present , but adequate hard rock for riprap could be developed from the terrac.!s or possibly the basalt dike in Tepee Park. Detailed geologic and geotechnical studies have not been made of the proposed dam and reservoir soltes. Such studies should include topographic snd geologic mapping, the drilling of holes for core and for testing of the permeability of the bedrock along the dam axis. Particular attention should be given to determining the engineering properties of the old landslide material, east of Beaver Creek. Suitable construction materials for an earthen dam are probably available locally. Sampling and testing will be required to determine the engineering properties of the materials. 3. Dam Layouts Dam and reservoir layouts were done at each of the project locations. Earthen embankment dams were laid out at both the upper and lower Beaver Creek sites. A maximum dam was estimated initially; dams providing 1/3 and 2/3 of the maximum reservoir storage were then laid out and the quantities and costs were estimated. This resulted in the following dam layouts and estImates: RESERVOIR CAPACITIES ESTIMATED Upper Beaver Lower Beaver Dams constructed of rolled-compacted concrete (RCC) were also considered. Because the foundation condi tions at the Lower Beaver Creek site were not favorable, an RCC dam was not considered there. IV-V