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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />results to match state boundaries, adjustments were made for utilities, such as Tri- <br />State, to exclude the effects of out-of-state service areas. Federal power generation <br />(USBR) in Colorado is included in the modeling in accordance with Western's <br />transmission systems and their marketing arrangements with the individual utilities. <br /> <br />Each utility was analyzed as a separate entity in order to determine effects that a <br />pumped storage unit would have on each system. The analysis reflected existing <br />limitations on transmission interconnections between utilities and alternate runs were <br />made to reflect possible future interconnections and major transfers of electricity over <br />and above those currently under formal arrangements. Stone & Webster estimated <br />the limitations between the utilities' systems based on previous studies done within the <br />state. <br /> <br />The second part of the analysis generated expansion plans that included generic <br />pumped storage additions which simulated both the pumping mode (pumping water <br />from the lower reservoir to the upper reservoir) and the generation mode of the <br />pumped storage facilities. The results of the case with pumped storage were <br />compared to those of the case without pumped storage. Annual costs for the entire <br />Colorado system were computed for both cases (with and without pumped storage) <br />over the 20-year study period, 1988 through 2007. <br /> <br />Because of the relatively long life of pumped storage facilities (50 years or more) an <br />extension period of 30 years was added in order to recognize important factors that <br />wo.uld impact economic feasibility. During the 30-year extension period neither the <br />amount and type of generating capacity nor the dispatch pattern was allowed to <br />change; however, fuel and variable operation and maintenance costs are escalated <br />and generating units which are retired are replaced with the same type of facility. <br />Annual costs for the entire Colorado system were computed for both cases (with and <br />without pumped storage) for the 30-year extension period. <br /> <br />The present values of the streams of future fixed and variable costs were computed to <br />determine the resulting net savings in system costs (if any) and were aggregated into <br />state totals. <br /> <br />2-3 <br />