C153629 Feasibility Study - Laserfiche WebLink

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I II I I I I I I I I I I I I I I I I I 24,000 acre-feet was below the minimum capacity to be considered and established the low point on the cost/capacity curve. The high dam at the upstream site was about the highest practical dam that could be fit into the topography without a very long cutoff wall on the left abut- ment ridge. The reservoir capacity of 89,700 acre-feet established the upper bound of the curve. The intermediate height dam was chosen to establish a mid-range on the curve. The downstream site elevations were the same as for the upstream site, so comparable points on the cost/storage curve could be established. In order to make valid cost comparisons, all RCC dam layouts were as similar as possible. Assumptions made for layout development include: o Diversion through a conduit embedded in a trench in the lower part of the abutment. The conduit can be used as part of the permanent outlet works. o Spillway - Ungated ogee section with flip bucket at dam toe sized for a peak probable maximum flood (PMF) discharge. o Outlet works consisting of an intake structure attached to upstream face of the dam, a conduit passing under dam, and a valve structure at downstream toe. o Formed conventional concrete facing zone at the upstream face. o Conventional concrete zone at the downstream face of both spillway and non-overflow section for protection against severe environment formed in steps sloping at 0.75 H : 1.0 V. 2. Rockfi11 Dam - 8ased on past experience with similar projects, it was judged that a rockfil1 or embankment dam at the Rock Creek sites would be more costly than an RCC dam. To confirm this judgment, a pre- liminary layout of a rockfil1 dam was made at the upstream site. A dam and spillway layout that best fit the topography determined the dam 3 - 3 6819W/502OW