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<br />. <br /> <br />. <br /> <br />. <br /> <br />Phase Two work may include one or more of the following possible work tasks: <br /> <br />a. <br /> <br />Preparation of Numeric Sediment Transport Model and Evaluation - In order to evaluate <br />the potential success of mitigation options which involve flushing or routing, it will be <br />necessary to develop a computerized sediment transport/deposition model of the reservoir <br />basin. This model will be developed using one of the existing modeling programs for <br />unsteady, non-uniform sediment transport such as MIKE 11 or MIKE 21C (developed by <br />the Danish Hydraulic Institute). This work will include a conceptual investigation to <br />determine the most appropriate software; calibration of the model using currently <br />existing stream concentration and flow data, data collected as part of this investigation as <br />well as existing reservoir sedimentation data; and running the model under various <br />anticipated or proposed conditions. In addition to modeling the effect of various <br />flushing/routing scenarios, analyses will be made of variations in reservoir operational <br />protocols on future sediment accumulation rates. <br /> <br />b. Dredging Disposal Sites - It will be necessary to enter into discussions with the owners <br />of potential disposal sites in order to assure that a suitable site can be obtained and to <br />assess the likely cost involved with developing such a site. Preliminary designs will be <br />provided for identified sites. It will also be necessary to determine the right of way <br />requirements needed to provide a discharge pipeline route from the dam to the disposal <br />site. <br /> <br />c. <br /> <br />Drainage Basin Yield Reduction - Further investigations will be conducted related to any <br />methods which are identified in the Phase One evaluation as having a potential for <br />economical success. The related Phase Two work will include obtaining field soil <br />samples and performing investigations into the costs involved and the likelihood of <br />success for these options. For example, if it is found that active slides comprise a <br />significant source of sediment, shallow soil samples will be obtained and tested, the slide <br />characteristics will be further investigated and preliminary stability evaluations will be <br />performed to identify possible stabilization alternatives. It is not intended that this work <br />will include detailed geotechnical investigations or analyses. <br /> <br />d. Preliminary designs may be performed for installation of a low-level outlet gate. This <br />work will include collaboration with the U.S. Bureau of Reclamation which retains safety <br />and technical oversight of the facility. <br /> <br />2. Monitoring and Sampling - It is anticipated that sediment monitoring stations will be <br />established at two locations. These locations will be immediately upstream from the reservoir <br />(probably located near the existing flow gauging station) and immediately downstream from the <br />reservoir. These stations will provide a means to start gathering baseline data for such tasks as <br />correlating the stations with total trapped sediment, correlating with runoff rates, identifying <br />seasonal variations in sedimentation and establishing patterns of sediment inflow and outflow <br />which will be needed to implement a flushing or routing protocol. This task will include the <br />following: <br /> <br />a. Each station will include means to monitor water turbidity, temperature and <br />conductivity. The turbidity probe will be tethered at the most appropriate location and <br />depth in the stream in such a way that it will rise and fall with the stream stage. <br />b. Each station will also include the ability to monitor stream stage. <br /> <br />4 <br />