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UPCO/Summit County Water Supply Study <br />December 15, 2004 <br />1947 1961 1973-1979 <br />1949-1952 1963-1965 1981-1982 <br />1954-1955 1967-1969 <br />The approach for the Clinton Reservoir re-operation alternative differed from the approach for <br />new storage sites. As for the other alternatives, available inflow hydrology was estimated using <br />PACSM, considering both water that could be stored under Clinton Reservoir's priority (but <br />unconstrained by reservoir capacity), and water that could be stored assuming that a replacement <br />supply could be made available to Dillon Reservoir. Unlike the other storage options described <br />above, the yield of this option is almost entirely dependent on the exchange supply rather than <br />the inflow hydrology. This is because the reservoir generally remains full and supply above <br />Clinton is needed only occasionally. For the purposes of this study, it was assumed that available <br />inflow to Clinton would not limit the reservoir's ability to remain full. The inflow hydrology <br />analysis generally supports this assumption. An operational spreadsheet was then created and <br />operated to simulate one manner of re-operating Clinton Reservoir, using the exchange supply <br />estimated far one of the replacement supply alternatives. The spreadsheet is described in more <br />detail in the subsection on Clinton Reservoir re-operation. <br />Project cost for reservoir construction was based on a unit cost of $14.80/cu yd of embanlcinent <br />volume, which includes design and construction contingencies of 40 percent and an allowance of <br />4 percent for permitting. This value reflects recent reservoir project engineering done by Boyle, <br />as well as a recent study of the Swan River site (GEI, 2003). Not reflected in the construction <br />cost are expenses related to land purchase, water rights acquisition, environmental mitigation, or <br />the replacement supply needed to realize the potential yield by exchange. <br />Middle Fork Swan River Reservoir <br />This reservoir site is located on the Middle Fork Swan River, as shown in Figure 2, <br />approximately 800 feet above the point where it joins the North Fork to form the Swan River. <br />The proposed embankment would be in Section 24, T. 6 S., R. 77 W, and drains an area of 14.5 <br />square miles The reservoir footprint at any significant size would encompass private, National <br />Forest, and City-owned land. Above a water surface elevation of 9,860 feet, it would also <br />encroach on land owned by Summit County. Aerial imagery shows a group of structures on the <br />east side of the river, perhaps a camp or ranch outbuildings. USGS mapping shows two sites <br />marked as "Masonic Monument (Historical)", near the extent of the reservoir shown here. <br />There are no conditional reservoir rights at this specific site in the State Engineer's tabulations. <br />However, two different conditional storage rights are located shortly downstream, at the Swan <br />River Reservoir site described below. One is owned by the Town of Breckenridge and the other <br />by Summit County. The Town's water right is for 9,100 af and the County's water right is for <br />11,560 af. Both are junior to Roberts Tunnel and Dillon Reservoir, but senior to minimum <br />instream flow rights held by CWCB and to the Dillon refill right. In the PACSM analysis, it was <br />assumed that one of those water rights could be transferred to this site; however, it was also <br />assumed that a minimum bypass equivalent to the CWCB right would be observed, regardless of <br />seniority.