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<br /> <br />prepared by an experienced hydro planner to take <br />advantage of the topography, geology, accessibility <br />(and,if a redevelopment, the existing structural com- <br />ponents of the dam, spillway, and power plant, as well <br />as adjacent, nonproject structures), the process of <br />selecting installed capacity begins. <br /> <br />Normally, a flow duration curve is prepared to aid in <br />making the selection of trial plant capacities. <br />Installed plant capacities in the range of 15 percent to <br />40 percent flow exceedance are usually selected to <br />cover the normal range over which small hydroelectric <br />plants are optimized. However, multiple units will <br />present a range of exceedances. This spans the range <br />of flows from somewhat less than average annual flow <br />to about twice average annual flow. <br /> <br />For each of the trial installed capacities, costs are <br />computed for all electrical, mechanical, and civil <br />works. Allowances for contingencies and the costs <br />associated with engineering, legal, administrative <br />services are added to arrive at the total construction <br />cost. Interest accrued to the project during construc- <br />tion is also considered and is accounted for in the <br />analysis. Several manufacturers of small hydro equip- <br />ment are contacted to solicit cost information and <br />performance data. Past quotes provided by manufac- <br />turers for other similar projects are also consulted to <br />provide additional cost information. <br /> <br />The annual cost for each trial plant capacity is com- <br />puted based on the cost of money, overhead and <br />maintenance charges, interim replacements, insurance <br />and taxes. Associated benefits to the project are <br />computed using flow data taken from USGS gage <br />records and pro-rated to the site. Usually an average <br />year is selected and average daily discharges used to <br />calculate energy production. A computer is the most <br />efficient way to make these calculations. Input data <br /> <br />29 <br />