Fig. 6. Section through the spillway dam along center line of one of the buttresses that support the Stoney gates to control the water level. The results given in the above table are also shown in diagram (Figs. 3 and 4, pages 345 and 347). Fig. 3 shows that for average years the minimum horsepower available will be 15,400, increasing with discharge up to 98,200 horsepower and then decreasing to 70,200 horsepower in high floods. AUXILIARIES. As indicated before, for dry years any deficiency in water power will be met from steam auxiliaries. These are already in place. The steam plant lighting the Capitol, Library of Congress, Senate and House Office Buildings, Coast and Geodetic Survey Building, etc., has a capacity of over 10,000 horsepower, and will supply all necessary deficiencies in dry years for a long period. When the limit of this plant is reached, either additional steam auxiliaries may be constructed in connection with the heating plant of any new Government building or it may prove better to develop the unused fall of 33.5 feet at Great Falls. GENERAL DISCUSSION. Mr. Herschel assumes as his unit of power a 12,500-horsepower turbine. Two such units will be needed to meet present requirements, including peak demands. With a third unit as a reserve, the installation will be complete for existing needs. As consumption increases more units will be needed, until for the 47,000-horsepower maximum predicted in 1937 four such units will be required, with a fifth for reserve. A power-house to accommodate this number of units should, however, be built at once, as a matter of economy; and as it is proposed as previously indicated, to provide for the increased water supply by pumping from the power lake, space for these pumps must also be provided. Table 2, before given, shows that for one-half of the average year 66,000 horsepower for the twenty-four hours is available from the river discharge. This would represent a peak load of about 100,000 horsepower, using 11⁄2 as the ratio between the average load and peak load. It is calculated that out of a total of 438,000,000 kilowatt hours output for the average year, auxiliaries would have to furnish but 99,000,000, and would be in operation but half the year. This larger development could be obtained by extending the powerhouse so as to contain four additional turbine units, and in the design adopted the foundations of the power-house and the intake dam itself are arranged so that these four additional units may be Fig. 7. Section through dam and power-house along center line of draft tube, showing one of the nine turbines in complete plan. installed, should Congress decide so to do, either by itself or by agreement with a power company. WORKS PROPOSED FOR POWER DEVELOPMENT. The chief features are the dam, power-house, hydraulic and electrical appurtenances for power and turbine pumps, and pipe lines for the water supply. The plan of the dam and power-house is shown on Fig. 5 (page 349), while Fig. 6 (page 351) gives a section of the dam through the center of one of the buttresses supporting the Stoney gates. The dam is curved in plan, but of gravity section, with eighteen Stoney gates operated from a tunnel left in the masonry of the dam. These gates, as already stated, are to provide additional discharge area in floods. A small footbridge connects the piers between the gates, and a floating caisson is provided which can be floated to and made to close any opening on the upstream side of the gate, which can then be repaired. The three Stoney gates. next to the power-house have hinged tops to facilitate passing ice, drift, etc., through the dam without too much loss of water, and for the same purpose an auxiliary spillway is provided near the shore end of the power-house. The foundations of the dam are apparently excellent, but detailed information could not be obtained within the limits of available money. The dam in its gen eral features resembles the Gatun Spillway dam of the Panama Canal. The power-house and intake dam are shown on Fig. 7 (page 353). The proposed location is just within the District and distant about 5 miles from the Executive Mansion. This short distance permits the omission of step-up transformers and thus simplifies the electrical installation. The usual traveling crane for handling the heavy machinery is included, together with a small heating plant, store rooms, workshop, and other minor accessories. The power-house is protected by the intake dam, which is located just above it and through which pass the penstocks leading to the turbines. The intake openings are protected by specially designed racks. The intake house over the intake dam furnishes shelter to the operating force in inclement weather, protects the racks, and contains a light traveling crane. This latter may be used in cleaning out the racks or to place a stop gate over any penstock opening desired. The turbines are of 12,500 horsepower capacity each and are di |