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r <br /> PUMPING REQUIREMENTS AND WATER LEVELS <br /> The inflow scenario described above was modeled to determine the required <br /> pumping capacity. The results show that one 629 pump could adequately return the <br /> subdrain, EPR return, and tributary runoff flows with a maximum change of storage in <br /> Robinson Reservoir of about 1,000 acre feet or less, depending on the number of stages <br /> in the pumps. Two 629 pumps would have the capability of fully controlling the reservoir <br /> levels with minimal increase in storage during runoff, an ideal situation. <br /> Previous evaluation of the pump characteristics for the 629 pumps revealed that <br /> there are two practical options for configuring the pumps. To provide the pump capacity <br /> proposed in the original design, reconfiguring the pumps to a four-stage system was <br /> believed to be the best arrangement because it would minimize the use of the third pump <br /> in wet years. For the revised alternative, the four-stage arrangement would still be <br /> preferred. The four-stage option would yield pump capacities of 2,500 gpm for the first <br /> pump and 4,300 gpm for two pumps in parallel. <br /> The fact that two of the 629 pumps will provide excess capacity for the system <br /> begs the question of whether smaller pumps should be considered. The 629 pumps cannot <br /> be modified for lower capacity without incurring a significant penalty in efficiency. We do <br /> not recommend smaller pumps for the following reasons: <br /> 1. The reuse of the 629 pumps, with a reported excellent history of <br /> maintenance, is a distinct advantage. This is particularly true since they are <br /> already stainless steel and relatively minor adjustments are needed to <br /> convert them for use at the pump station. The cost for purchasing smaller <br /> stainless steel pumps would be much greater than modifying the pumps on <br /> hand. In addition, since only two pumps are recommended, the additional <br /> pump can be stored and reserved as a spare for future years. <br /> 2. The capacity of two 629 pumps to provide full control of the water level in <br /> Robinson Reservoir, even during high runoff years such as 1984 and 1995, <br /> should provide a comfortable margin of design such that floods of higher <br /> magnitude can likely be controlled as well. The modeling results for the <br /> existing and past system configuration and hydrology show that there is a <br /> marginal capacity for controlling runoff exceeding those years and that the <br /> 2 <br />