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Enlargement of Old Dillon Keservoir Engineering Fea.ribility Study <br />The conclusions and xecommendations for future work of the "Enlargement of Old Dillon <br />Reservoir Engineering Feasibility Study" completed by GEI Consultants, Inc. in June 1998 (see <br />Engineering Fea.ribility Study, E.xhibit J) were based on the understanding of the proposed pxoject, <br />site condirions, and the experience in dam evaluarion, design, and construction. The study <br />found that it is technically feasible to enlarge the e~sting Old Dillon Reservoir within the <br />scope currendy proposed. This information includes: <br />1. Surficial geologic mapping of the reservoir and surrounding area should be <br />performed to identify possible sources of on-site boYrow materials. After the <br />geologic mapping has been pexformed, a subsuxface exploration pYOgram should <br />be performed to investigate potential borrow materials (both low permeability core <br />and shell materials), as well as the foundation conditions beneath the e~sting <br />embankments and proposed new embankments. <br />2. Additional surveys should be performed to identify the dimensions and alignment <br />of the existing outlet woxks to Dillon Reservoix. <br />3. A survey should be perfoxmed of the e~sting access road alignment and <br />conditions to evaluate future upgrade needs. <br />4. A survey should be perfoYmed of the e~sting canal from the siphon at I-70 to the <br />reservoir. <br />Evaluation of Old Dillon Aeservoir First Enlargement <br />The conclusions of the "Evaluation of Old Dillon Reservoir Fixst Enlargement" completed by <br />the Colorado River Water Conservarion District (CRWCD) in December 2005 (.ree Evaluation <br />of ODK First Enlargement, Exhibit K) weYe: <br />1) The overall objective of providing additional water supply for Summit County, <br />Dillon <br />2) and Silverthorne from Old Dillon Reservoir First Enlargement as decreed in <br />Case No. 93CW288 can be physically served with diversions from Salt Lick <br />Gulch. At least 400 acre-feet in dry years and as much as 1200 acre-feet in wet <br />years can physically be diverted from Salt Lick Gulch to Old Dillon Reservoir. <br />This is ample water to fill the existing pool in Old Dillon Reservoir and the 150 <br />acre-foot enlargement pool granted in Case No. 93CW288. The legal ability to <br />undertake these diversions is subject to the underlying water rights, the <br />alternate points of diversion, changes of water rights and exchanges decreed in <br />Case No. 93CW288, the rights granted via the Denver Subordination and <br />Colorado's prior appropriation system. <br />3) The 150 acre-foot Old Dillon Reservoir First Enlargement was found to be <br />technically <br />4) feasible in previous studies conducted by Sumtnit County9. Environmental <br />impacts can be mitigated on site.~o Costs of the Old Dillon Reservoir First - <br />Enlargement and related physical facilities may be between $3.5 and $4.7 <br />million depending on many factors discussed below. <br />5) Summit County's rights in the Old Dillon Reservoir First Enlargement can be <br />used <br />5 <br />