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CHAPTER III PLAN FORMULATION Benefits Benefits used in evaluating alternative plans were based on the cost of the most likely single-purpose alternative which could deliver the same type of benefit to the same service area. Considering a plant factor of 9 percent, the most likely alternative would be a combustion turbine system using Federal financing and real fuel escalation factors. The capacity value was based on a peakload plant. The energy values were based on fuel and operation and maintenance costs. Ninety percent of the value is fuel and 10 percent operation and maintenance. The fuel portion was escalated by a factor of 2,05 to account for a possible increase in fuel costs over and above the general level of inflation. Based on the above criteria and using a 9 percent plant factor (800 operating hours per year), benefit values were determined to be $30 per kW for capacity and 185 mills per kilowatthour (kWh) for energy. Costs Cost estimates for the powerplants and related facilities used in the alternatives were developed using a feasibility design obtained by contract in September 1980 for the Rim Basin pumped-storage unit, a potential feature of the Dominguez Project near Grand Junction, Colo., and unit costs developed by Reclamation, These unit costs considered designs for the Diamond Fork Power System, a potential pumped-storage feature of the Bonneville Unit, Central Utah Project, and the Hoover Powerplant Modification, a Reclamation facility in Nevada. The cost of earthfill dams used for forebays, afterbays, and cofferdams was estimated using Reclamation's .FLODAMP computer program, and the cost of access roads was estimated using Reclamation's earthwork computer program, Concrete dam estimates were obtained by estimating mass concrete quan- tities and applying a cost per cubic yard. The design criteria used for sizing alternative features include (1) forebay capacities based on 12-hour storage, (2) flow rates based on forebay and afterbay water surface elevations at two-thirds of maximum depths, and (3) penstocks and tailraces sized with maximum velocities of approximately 20 and 7 feet per second, respectively. Costs were estimated based on the January 1981 price level and indexed to January 1982 levels. An interest rate of 8.375 percent was used in all estimates; this was the plan formulation rate expected to be in effect in fiscal year 1985 when the Regional Director's Planning Report/Environmental Impact Statement was scheduled for completion. Interest during construction was estimated using compound interest assuming an equal amount would be spent each year of construction. Capital costs were amortized assuming a 100-year life, Annual opera- tion, maintenance, and replacement costs included those for the pump/ generator plant, transmission facilities, administrative expenses, and replacement items, Power costs were based on the energy required to pump water into the forebay (1.5 times the amount generated) at 41 mills 9