C153445 Feasibility Study - Laserfiche WebLink

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The south dike is the shor~est section, only ten feet high, of the dike forming Summit Reservoir and it is in the worst condition. The thick brush makes it very difficult to inspect the dike and water is ponded along~he toe for most of the length. There are three sections to the south dike; east, west and middle. Each section has a ditch which was cut to drain the ponds but there is not sufficient gradient to accomplish that result. As part of the recontouring, the drains will be constructed properly, and flumes installed. The middle section will require structural improvement immediately; this section is about 450 feet long. There are two areas were water is seeping through the foundation. The water is clear gnd the seeps appear stgble; no observable fines are being carried. There are also seeps through the embankment in this section. In order to assure the integrity of the embankment a filter blanket and berm will be constructed over the middle section beginning at the dike crest and extending out 50 feet. The design criteria and exact plan are described later in this chapter. Similar filter blankets may be required on the other sections of the dike eventually, therecontouring, and measuring flumes will allow monitoring to determine when and if the work is required. An inspection and monitoring program will be developed and imple- mented at the conclusion of construction. The crest of the dike will also require some work to raise low areas. Six areas were identified, by a level line across the crest, that have less than three feet of freeboard. The worst location had only two feet, there were two areas with 2.5 feet, and the other areas had 2.7 feet of freeboard. In total there is q.bout 860 linear feet of dike that needs to be raised. The last aspect of the physical plan is the abandonment of the west outlet pipe on the dam. The outlet has not been used in many years and poses a safety ha~ard to the darn. The east outlet is in good shape and will provide sufficient capacity for draining the reservoir and serving the ir~igated area. The outlet is 24 inches in diameter and is 100 feet long. The outlet pipe was plugged by putting a bulkhead on the reservoir side of the pipe then filling the pipe with grout from upstream to downstream. There is a pond at the outlet formed by wood cribbing that would be removed and filled. A pipe drain would be installed to remove any seepage that may occur along the outlet pipe. In summary the physical plan includes the following items: 1. Recontouring the ground below the dike to remove ponds, preclude future ponding, recut surface drains, and install measuring flumes. 2. ,Raise low sections of dike crest to provide three feet of freeboard. , 3. Backfill below the west outlet. -20-