PROJ00519 - Laserfiche WebLink

Home Browse Search

I- I I I I I I I I I I I I I I I I I I Woodward. Clyde Consultants The present seepage condition and a subsequent restriction issued by the State Engineer's Office have necessitated draining of the reservoir until the seepage condition is remedied. In addition, previous reports including the US Army Corps of Engineer's Phase I Inspection Report and several State Engineer's Office reports have emphasized the lack of adequate spillway capacity to pass the 75% PMP flood. The scope of modifications to Douglas Dam include design modifications to correct the seepage condition and construction of spillway modifications to facilitate handling of the 75% PMP flood. In its present condition, Douglas Dam is not capable of storing any water. Furthermore, in the event of flood conditions during which the outlet works is not able to pass all inflow to the dam as quickly as it enters the reservoir, some water may be stored in the dam which would result in unsafe conditions. Douglas Dam has to be rehabilitated or breached before the next spring runoff given its present condition. 5.1.2 Proposed Improvements The rehabilitation alternatives for Douglas Dam were designed to reduce the seepage in the area of the outlet pipe, upgrade the existing spillway, extend the existing toe drain system, and install piezometers and movement markers. Seepage reduction concepts include placement of cutoff collars on pipes which pass through the embankment; construction of barrier walls either upstream or at the midpoint of the embankment; or removal and replacement of sections of the embankment. Rehabilitation measures will also include modifications such that the spillway can handle 75% of the PMP flood. Piezometers and movement markers will be installed to monitor the phreatic surface and movement of the embankment. 22539G/DOUGLAS.DAM 12.17.90/REPORTS3 22