C150295 Feasibility Study - Laserfiche WebLink

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2.3.2 Watex Supply Demands There is a demonstrated need for additional water supply in Sumnut County as documented in the Upper Colorado River Basin Report, Phase II (LJPCO). Participants in the UPCO study were Grand and Sumniit Counties, Colorado River Water Conservation District (River District), Middle Paxk Water Conservancy District (Middle PaYk), Northwest ColoYado Council of Government's Water Quality and Quantity Cominittee (Q~, Northern Colorado Water Conservancy District (Northern), Denvex Water (Denver) and Colorado Springs. The UPCO study identified a total future demand for an additional 9,900 AF for municipal supply and snowmak~ng in Suininit County, with 25% of that (2,475 AF) demand fxom areas upstYeam of Dillon Reservoir. A maximum annual shortage in existing supply of 1,900 AF was idenrified in the UPCO study; however, addirional future demands in the unincorporated aYeas of Suintnit County was not modeled. The ODR pYOject satisfies only part of the idenrified need, but does so by enlaxging an e~sting reservoir and delivering wateY into the Upper Blue RiveY basin from below Dillon Reservoix, thereby creating a uniquely desiYable project foY the Sununit County community. The demand will increase by 196% at buildout of 3,316 EQRs. Currently the limiting factor fox wastewatex is 2,100 EQRs, however the sewer treatment plant can be expanded to meet futuxe demand (,ree i~ater Sy.rtem Demand, Exhibit 0~. Hydrology foY the enlargement was initially studied by the group in a xepoYt entided "Old Dillon Reservoir Inflow Hydtology Investigation and Outfall Pipeline Investigation" completed by Resource Engineexing, Inc. completed in April 2005 (.ree ODR Hydrology I~e~iort 2005, Exhibit P~. "FYOm this analysis RESOURCE concludes that the amount of water that can be diverted into Old Dillon Reservoir in a very dry yeax is between 400 and 700 acre-feet and is insensitive to ditch capacity above 10 cubic feet per second. In an aveYage yeax the potential diversion ranges from 700 to 1200 acre-feet with no benefit of expanding the ditch capacity above 10 cfs. In a wet year the yield is expected to Yange between 600 and 1700 acxe- feet with significant yield increase xealized with each additional increment of ditch capacity (Note that the wet yeax yield pxedicted by the gauge is less than the average year yield. This is a function of the wet year chosen [1984] in which the hydtograph exhibited a high peak flow over a narrow time period. This contrasts with the average yeax hydrogxaph which exhibits a lower peak flow spread ovex gYeateY duration). Two key assumptions employed in the hydrologic analysis are: 1. The Dillon Ditch will divert all available stream flow up to the maximum capacity of the ditch (5, 10 or 15 cfs). 2. The diveYSion season commences on April 1 and ceases on July 15. Varying either of these assumptions will impact the yield estimates. For example, imposition of a bypass flow will reduce the yield, while extension of the diversion season beyond July 15 would increase the yield, particularly in average and wet years." ResouYCe Engineering, Inc. updated the 2005 study in gxeateY detail, however that study is still in draft form. The pYOponents would operate the reservoir as a joint enterprise to meet the water requirements of each goveYnment entity in accordance with their xespective wateY xights. 9