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<br />I <br /> <br />I <br />I <br /> <br />5.0 <br /> <br />DESIGN CONSIDERATIONS AND PROJECT COSTS <br /> <br />5. 1 GENERAL <br /> <br />I <br />I <br /> <br />The operations study concluded that a reservoir capacity of 2,900 <br />acre-feet would be required to meet the project water demands in a drought <br />year such as 1977. <br /> <br />I <br />I <br />I <br /> <br />Construction of a 2,900 acre-foot reservoir at the Snowball dam site <br />would require a dam 138 feet high with a crest length of 1,800 feet. <br />Excellent clay borrow materials exist within 1,000-feet of the dam in both <br />the spillway area on the right abutment and approximately 200-feet north of <br />the left abutment. Sufficient quantities exist for the construction of a <br />homogeneous embankment. The design parameters for the various components <br />of the dam are discussed in detail in Sections 5.2 through Section 5.7. <br /> <br />I <br />I <br /> <br />5.2 EMBANKMENT DESIGN <br /> <br />I <br />I <br /> <br />The results presented in the geotechnical report, located in Appendix <br />A, indicate that embankment slopes of 3:1 for the upstream dam slope and" <br />2:1 for the downstream dam slope will provide adequate safety factors for <br />stability purposes. Several existing dams have been constructed on shale <br />foundations with similar slopes including Taylor Draw Dam in Rangely, <br />Colorado and Monticello Dam in Monticello, Utah. Jerry Creek Dam near <br />Mesa, Colorado and Yamcolo Dam near Yampa, Colorado are further examples of <br />dams with similar slopes and embankment materials which have performed <br />satisfactorily. Based on these recommendations, the dam slopes described <br />above were adopted for feasibility level design. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The borrow material available for embankment construction consists of <br />a stiff, nearly impermeable clay with some rock material. This material <br />has excellent permeability and strength characteristics for use in a <br />homogeneous embankment. Filter material, rip rap , and riprap bedding are <br />not readily available near the dam site and will have to be imported from <br />sources near Pagosa Springs. The filter material will be comprised of a <br /> <br />5-1 <br />