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<br />. <br /> <br />2. Peer Review of Previous Studies - Previous studies conducted by Western Engineers <br />include the following: <br /> <br />April 2005 - Preliminary Dredging Feasibility Study <br />May 2006 - Evaluation of Historic Sediment Surveys <br />February 2007 - Preliminary Evaluation of Sediment Mitigation Options <br /> <br />A review of this information will be conducted by a firm or individual with broad experience and <br />expertise in reservoir sedimentation. A preliminary report will be prepared discussing the results <br />of the peer review including comments regarding validity of conclusions <br /> <br />3. Collection of Additional Data - This task entails collecting the following information: <br /> <br />a. Hydrologic data (stream flow and rainfall data). <br />b. Sediment sampling and testing - Samples will be collected from the surface of the <br />sediment at 10 to 15 locations. These samples will be tested for grain size distribution, <br />index properties, moisture content, organic carbon content and agronomic characteristics. <br />Selected samples will be tested for hazardous constituents. <br />c. Grab samples of the inflow and outflow water will be obtained several times <br />during the season and the samples will be tested for solids concentration plus the <br />characteristics listed above for the sediment samples. It is anticipated that 10 to 15 of <br />these water samples will be obtained and tested. <br /> <br />. <br /> <br />4. Feasibility Evaluation of Optional Sediment Management Techniques - A range of <br />possible mitigation options will be considered and evaluated as discussed below: <br /> <br />. <br /> <br />a. Pressure Flushing - Pressure flushing is executed with a high water surface <br />elevation in the reservoir and entails opening a low-level gate at the dam. This flushing <br />technique is usually implemented solely to clear deposited sediment from the immediate <br />area in front of low level outlets. Pressure flushing leads to the development of a cone- <br />like space upstream of the outlet, which is cleared of sediment. <br />b. Drawdown Flushing - Drawdown flushing is used to remove deposited sediment <br />from the reservoir bed. The objective with drawdown flushing is to draw the water <br />surface elevation in the reservoir down sufficiently to result in river-like flow conditions <br />in the reservoir that will lead to re-suspension of deposited sediment and its discharge <br />downstream of the dam. Such operation requires a low-level outlet with sufficient <br />discharge capacity, and at a low enough invert, to develop the desired flow conditions. <br />Once the river-like flow conditions have established it is necessary to discharge enough <br />water through the reservoir to re-suspend the sediment and discharge it downstream of <br />the dam. <br />c. Reservoir Routing - This option entails creating flow conditions in the reservoir <br />during flood flows that will, ideally, transport incoming sediment through the reservoir <br />without deposition. This technique does not increase reservoir capacity, because it does <br />not re-suspend any significant amounts of deposited sediment. The main goal is to <br />prevent additional sedimentation by conveying incoming sediment through the reservoir <br />without deposition. The investigation of routing or flushing options will also involve <br />evaluation of the feasibility for installation of a low-level controlled outlet. <br />d. Mechanical Dredging - Mechanical dredging involves using a mechanical dredge <br /> <br />2 <br />