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<br />of and outside the 32-foot-wide boatchute will not adversely affect flow patterns. However, a pilot <br />rock should not be used on the right side of boatchute 1 since space is not available in this area. <br /> <br />The final design of the boatchutes was optimized for a riverflow of 500 ft' I s; however, the wave <br />characteristics are acceptable throughout the entire range of boating flows from 50 ft'/s to <br />3,000 ft'/s. <br /> <br />The relative elevations between the ramps in boatchute 2 and the weir elevations in boatchute 3 <br />are the same as those between boatchutes 1 and 2 (fig. 28) even though the head drop over the <br />second chute was less than over the first. The model tests indicate that the elevations of the ramps <br />in the upstream chute can be off by :!: 4 inches and the wave characteristics will still be adequate. <br />The configuration reported provides optimum performance. <br /> <br />These guidelines should be followed when using the standard boatchute design developed in this <br />model study: <br /> <br />1. The second ramp in the boatchute should be placed at an elevation 0.4 foot above the <br />design elevation (defined in fig. 27) of the downstream control. <br /> <br />2. Both ramps should be 10 feet long and 0.75 foot high; the top of the ramps should be <br />horizontal. <br /> <br />3. The slope of a line connecting the crest of the dam with the lip of the second ramp should <br />be Ito 10 (fig. 4). <br /> <br />4. A low flow notch should extend from the crest through the first ramp. <br /> <br />The general boatchute configuration is acceptable for head drops from 2 to 3.5 feet. The length <br />of the boatchute will increase as the head drop increases. <br /> <br />Both boatchutes were tested in the laboratory for river discharges ranging between 100 and <br />3,000 ft'/s. Photographs of boatchute operation with final design configuration are shown on <br />figures 29 through 33. <br /> <br />Flow patterns. - Time lapse photographs of 8-foot boats approaching Union Avenue dam and <br />traveling between boatchutes 1 and 2 were used to define flow patterns. Lights on the boats <br />produced streak lines. The grid spacing was 18 feet prototype. A strobe unit flashing at constant <br />time intervals (lit) produced images of the boats. The velocity of a boat during each interval can <br />be determined by dividing the distance the boat traveled by llt for the photograph. <br /> <br />Surface velocities and flow lines are shown on figures 34 and 35 in the approach channel to Union <br />Avenue dam at flows of 1,000 and 1,500 ft'/s. Surface velocities and flow lines in the pool between <br />boatchutes 1 and 2 are shown on figures 36 through 38 for discharges ranging between 500 and <br />1,500 ft'/s. Figure 39 also shows the path of a boat passing over the main crest. <br /> <br />The model tests indicate that a boat will take approximately 1 minute (prototype) to float from <br />boatchute 1 to boatchute 2 at 500 ft'/s. At 1,500 ft'ls, it will take about 30 seconds to reach <br /> <br />9 <br />