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<br />or main channel pool) nearest each <br />selected beach would be located. <br />Small portable equipment would <br />be transported downstream by raft <br />to various sites in the Grand <br />Canyon. A temporary small banier <br />or berm to contain the pumped <br />sand would be constructed on a <br />beach. A sediment-water mixture <br />would then be pumped into the <br />diked area. Water would then <br />drain back to the river through the <br />barrier or underlying beach and the <br />pumped sand would remain on the <br />beach. The barrier would be <br />removed at the end of the pumping <br />operation. The newly deposited <br />sand would form a more natural <br />slope after being reworked by wind <br />and water. <br /> <br />The sand pumping operation <br />would most likely take place <br />during the months of January or <br />February when recreation use is at <br />its lowest level. This concept <br />would be very flexible because both <br />the number of beaches targeted and <br />frequency of the sand pumping <br />could be varied as needed, if the <br />channel-stored sediment is <br />available. In this alternative, it <br />would be applied on a one-time <br />basis, to restore selected beaches <br />with the assumption that sand <br />added to the river with the slurry <br />pipeline would help maintain <br />beaches in the future. <br /> <br />Multi-level Intake Structures <br /> <br />Prior to the completion of Glen <br />Canyon Dam, the temperature of <br />the Colorado River varied <br />seasonally and ranged from 32.4 <br />degrees Fahrenheit ("F) to 82.4 "P. <br />Since the completion of the dam, <br />seasonal temperatures have <br />recently ranged from 41.9"F to 53.6 <br />"P. The river water temperature at <br />Lees Ferry for the months of May <br /> <br />through October averages about 50 <br />"P. <br /> <br />Water released from Glen Canyon <br />Dam for the production of <br />hydroelectricity is withdrawn at an <br />elevation of 3470 feet. This <br />elevation is 230 it below the water <br />surface of Lake Powell when the <br />reservoir is full (elevation of 3700 <br />feet). <br /> <br />The temperature of the water <br />released from the dam could be <br />increased by withdrawing water <br />from a warmer level of the <br />reservoir. This would be <br />accomplished by attaching a <br />multi-level intake structure (also <br />referred to as a selective <br />withdrawal structure) to each of the <br />eight existing is-foot diameter <br />penstocks. Each structure would <br />include a series of vertically stacked <br />gates that would enclose each <br />penstock intake. Different <br />configurations of gates could be <br />opened to mix water of varying <br />temperatures. Gate control would <br />be automated and adjustments <br />made in relation to reservoir <br />elevation, turbine operation, and <br />water temperature. <br /> <br />Preliminary studies indicate that <br />selective withdrawal structures on <br />each of the eight existing penstocks <br />could potentially increase the <br />downstream river temperature 5 to <br />18 "P above present conditions <br />(river temperatures between 54 and <br />69 "P from May to October). This <br />potential increase is still 7 to 16 "P <br />cooler than pre-dam conditions. <br />These temperatures represent the <br />upper range of possible <br />temperatures and not necessarily <br />the optimum temperature for <br />native fish or any other resource. <br />Temperature operations could be <br />adjusted on a seasonal basis to meet <br /> <br />ecological objectives, although this <br />would involve complex factors. <br /> <br />The Historic Pattern alternative <br />would be a refinement of the <br />preceding alternative, but with <br />maximum releases restricted to the <br />operational capacity of the <br />powetplant, and monthly and daily <br />releases held at steady levels <br />generally reflective of pre-dam <br />patterns. <br /> <br />Minimum flows would range from <br />4,200 ds in January to 33,200 cis in <br />May and June, based on historic <br />seasonal patterns. Maximum <br />monthly flows would be <br />determined by the monthly volume <br />to be released. The powetplant <br />capacity would be exceeded only <br />during floods when the reservoir <br />would be full. Annual release <br />schedules would be updated <br />monthly based on updated <br />streamflow forecast information (as <br />at present). The maximum change <br />in releases to adjust flows for <br />forecast changes between months <br />would be 2,000 ds per day. Power <br />operations would be determined <br />almost entirely by the water <br />releases. <br /> <br />As with the previous alternative, <br />sediment augmentation, pumping <br />river bottom sand, and multi-level <br />intake structures are part of this <br />alternative. <br /> <br />STEADY FLOWS <br /> <br />The objective of each of the three <br />steady flow alternatives is to <br />eliminate daily fluctuations and <br />minimize other variations in water <br />releases to provide a moderated <br />and relatively constant <br />downstream environment. This <br />objective is addressed on an annual <br />basis, a seasonal basis, and a <br />monthly basis. <br /> <br />~ <br />