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Appendix D — Preliminary Design Summary <br />Lake Meredith was originally a natural lake, but was enlarged by the Lake <br />Meredith Reservoir Co. to its current capacity of 41,400 acre -feet and a surface area of <br />5,742 acres. The reservoir receives water deliveries from the Arkansas River through <br />the Colorado Canal and from Bob Creek, a natural tributary. The natural depression <br />was converted to an operating reservoir by constructing an outlet channel that is <br />currently about five miles long and 100 feet wide. The route of the original channel is <br />through the low area, or thalweg, of the natural basin. The capacity of the outlet channel <br />is 200 cfs to 800 cfs. <br />As sediment loads from the Colorado Canal and from Bob Creek have <br />accumulated in the reservoir over the decades, the fine fractions of sediment (clay and <br />colloid size) have settled out in the low, deeper pools of the reservoir. During drought <br />conditions, and particularly in recent years, the Company has been forced to dredge the <br />outlet channel to make water deliveries from the lower storage of the reservoir. <br />Dredging is now required when the water surface is lower than 5 to 6 feet below high <br />water line. This restricts the use of 33 to 42 percent of the reservoir's contents to times <br />when the outlet channel is accessible and when the sediment is of a consistency that <br />can be effectively excavated. The material has become "thixotropic" slurry with the <br />consistency of pudding that flows back into the excavated space. Dredging attempts in <br />2002 were partially successful and very expensive. <br />The scope of the proposed project includes excavation of a new outlet channel <br />for the reservoir that will allow full use of the reservoir's contents. Other features of the <br />proposed design include measures that will prevent or minimize future sedimentation, <br />enhance the safety of the reservoir, facilitate efficient maintenance dredging of the <br />channel, allow installation of fish screens to preserve the fishery, and enhance the <br />removal of natural sediments from Bob Creek that currently accumulate in the reservoir. <br />The following is a summary of the features of the project, the result of an <br />alternatives analysis, a preliminary cost estimate, and figures that depict the preliminary <br />design of the channel and structural features. <br />