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<br />Final Draft - Preferred Storage Options Plan <br />Southeastern Colorado Water Conservancy District <br />June 8, 2000 <br /> <br />3.3.4 Enlargement of Non-Project Reservoir (Lake Meredith) <br /> <br />Five dam raise alternatives were evaluated for Lake Meredith, providing between 15,000 <br />and 75,000 af of additional storage capacity. Any enlargement of Lake Meredith <br />Reservoir by CSU would be subject to the stipulation with Proxy Group in Water Course <br />Cases 84CW62, 84CW63, and 84CW64. Enlargement by the District or another entity <br />would be subject to approval by the Lake Meredith Reservoir Company Board. Dam <br />modification concepts and preliminary cost estimates were developed by URS, Greiner, <br />Woodward-Clyde (URS) in 1998. URS concluded that raising the dam by up to 13 feet <br />(75,000 afofadditional capacity) would be technically feasible. Based on the URS work, <br />B&V prepared updated cost estimates for the following reservoir enlargements: <br /> <br /> Capacity Increase (AF) <br /> Existing 15,000 25,000 40,000 55,000 75,000 <br /> Normal Pool Elev. (ft) 4254.2 4256.0 4258.0 4260.0 4262.0 4265.0 <br /> Top of Dam Elev. (ft) 4257.0 4261.0 4263.0 4265.0 4267.0 4270.0 <br /> Nominal Increase in - 2 4 6 8 11 <br />. Normal Pool Elev. (ft) , , . . . . . <br /> <br />Principal elements of cost for raising the dam include: placing embankment fill material; <br />providing drainage and seepage control; providing upstream slope protection (soil cement <br />or riprap) to control wave erosion; armoring a portion of the dam with RCC to act as an <br />emergency spillway; and constructing a new multi-level intake and outlet works and a <br />morning-glory type spillway to pass up to the 100-year flood. The morning-glory would <br />discharge to a spillway outlet conduit. A key consideration at Lake Meredith is the <br />length of the embankment, which for the largest dam raise will be nearly 4 miles. <br />Seepage has historically been a problem at Lake Meredith and measures to control the <br />rate of seepage, and to safely collect and convey seepage that does occur, will be critical <br />design issues. <br /> <br />3.3.4.1 Environmental and Permitting Issues <br /> <br />Lake Meredith enlargement faces a significant wetland permitting hurdle that may be <br />difficult to overcome. It is expected to be difficult to gain approval for the inundation of <br />up to 1,200 acres of wetlands and then to develop successful mitigation for this loss. The <br />magnitude of impacted wetlands is sufficiently large to require a specific cost provision <br />for acquiring wetlands elsewhere as the assumed method of mitigation. An EIS most <br />likely would be required. If part of a larger project involving Project facilities or if <br />Project water is stored in an enlarged Lake Meredith, the USBR appears to be the likely <br /> <br />J \PROIECTS\9906I\Repons\Prderrcd SOP Final wpd <br /> <br />3-13 <br /> <br />~ GEl Consultants, Inc. <br />