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' <br />, <br />' <br />, <br />' <br />' <br />, <br />' <br />' <br />1 <br />' <br />' <br />' <br />' <br />, <br />Project Description and Alternatives <br />The purpose of this project is to replace two (2) existing outlet culverts at an upper and <br />lower reservoir in the Lost Park Subdivision in Park County, Colorado. The culverts are <br />both experiencing structural failure in varying degrees. Infiltration into the culverts has <br />been observed from CCTV televised inspections as well as debris accumulation inside <br />the conduits. Several breaks in the culverts were also noticn d• ad a aent to the culverts <br />struc tura l fai lures w h i c h are occurrin g, water migration (p p g) J <br />was observed. This is creating sink holes in the reservoir dams which may ultimate ly <br />lead to dam failure. The reservoir dams (2) have been inspected by the Office of the <br />State Engineer/Dam Safety Branch with a State mandate to repair the existing outlet <br />culverts. Currently, the State will not allow the upper reservoir to be filled. Three (3) <br />alternatives were considered: <br />1. The no-action alternative. <br />2. Line the existing culverts rather than removing and replacing with new culverts <br />($150,000). <br />3. Remove and replace the existing outlet culverts. Install new outlet structures <br />and valves, reconstruct the existing dams ($211,765.00) <br />ALTERNATIVE No. 1 was ruled out a� to be filled tim the r pa rs t h both <br />State will not allow the upper reservo <br />reservoirs are made. <br />ALTERNATIVE No. 2 was ruled out due to the current degree of pipe failure. Over the <br />years the culverts have been spot-repaired with differing materials and pipe diameters. <br />Lining the existing culverts would be marginal and the lining contractor could not <br />warranty the finished product. Further, lining the inside of the existing culverts would not <br />solve the greater issue which is the "piping" occurring adjacent to the conduits. <br />ALTERNATIVE No. 3 was selected as the most cost-effective ee r Thelselec�t ch. <br />This approach has the approval of the State Dam Safety Eng <br />alternative, Alternative No. 3, involves the removal of the existing outlet culverts (2) at <br />the upper and lower reservoirs. In order to remove the existing culverts the <br />embankment dams will need to be breached. <br />Proposed improvements include the replacement of the existing culverts with new 18- <br />inch HDPE culverts. New 2'x2' outlet structures, with stoplogs for monitoring water <br />release rates will be installed. In conjunction with the new outlet structures, new <br />screened intake structures and isolation valves will be installed. The breached dam will <br />be restored to approximately the same grades and configurations. New overflow <br />spillways, consistent with State standards, will replace the existing spillways which have <br />deteriorated over the years. <br />The estimated cost of the completed C nc I tua2 1 lans as pr paeed by Alpine�Wn is <br />' summarized in Table 1 and Table 2. p P <br />Engineering, Inc. are attached in the back pocket of this study. <br />' <br />' Stagestop Augmentation Reservoirs <br />Rehabilitation Feasibility Study <br />May 2010 <br />' <br />