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EXECUTIVE SUMMARY <br />This feasibility report was prepared by W. W. Wheeler and Associates, Inc. (Wheeler) for <br />the Parkville Water District (the District). This report documents the feasibility of repairs <br />to the District's Canterbury Tunnel water supply. The portal of the tunnel is located near <br />the East Fork of the Arkansas River approximately two miles northeast of Leadville, in <br />Lake County, Colorado. <br />The Canterbury Tunnel was constructed during the late 1920's to provide mine drainage. <br />It was driven approximately one mile into hard rock in a relatively unmineralized area. <br />The tunnel collected deep-seated water and transported it approximately 4,100 feet to a <br />portal where the water discharged into the East Fork Arkansas River. In 1961, Parkville <br />recognized that the tunnel produced high quality groundwater at a constant rate (625 <br />gpm), with a year-round temperature of approximately 50 degrees Fahrenheit. At that <br />time, Parkville constructed a wet well, pump station, and pipeline at the tunnel portal to <br />collect the water and pump it into the existing distribution system. From 1961 through <br />2003, the District used the water on a continuous basis throughout the winter and on an <br />intermittent basis during the remainder of the year. Beginning in the late 1990's, the <br />water discharged from the portal experienced turbidity spikes with increasing frequency <br />and the flow rate has gradually decreased to less than 200 gpm. In the summer of 2003 <br />the District stopped using the supply because of its diminished flow rate and <br />unpredictable physical quality. <br />Without the Canterbury Tunnel supply the District has had an increased number of <br />freezing and water supply problems in the distribution system. During the winter of 2009 <br />through 2010 over 200 service taps have frozen, at least five water mains have frozen, <br />over 100 customers are running water on a constant basis for freeze protection, and the <br />District's storage supplies are diminishing rapidly. Such problems threaten the water <br />quality of the District's supply and its ability to meet demand. Therefore, the Canterbury <br />Tunnel is a critical source of supply to the District because of its heat content and its <br />ability to supplement the District's physical supply during the summer days of peak use <br />and in winter months when the yield of its surFace water rights decline. <br />Based on Wheeler's and the District's observations of the tunnel structure during various <br />site visits over the last ten years; it is Wheeler's opinion that the tunnel structure is <br />deteriorating. It is believed that the tunnel was constructed through glacial till material <br />with timber cribbing as wall reinforcements for at least the first 1,200 feet of its length. <br />The remainder of the tunnel was driven into hard rock that did not require continuous <br />structural support. The objective of the repairs is to develop a facility that will restore <br />access to this critical source of high quality water to users in their service area. The <br />warm temperature of the source is also critical to minimize freezing problems throughout <br />the District's distribution system. <br />In accordance with CWCB guidelines, Wheeler has developed the following repair <br />alternatives: <br />__J W. W. Wh¢eter and Auociates, Inc. 5/19/2010 Final <br />— �1 Woter Rssourc¢s Enginaan Page i <br />