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<br />.. <br /> <br />DRAFT <br /> <br />right side of the second dam was brought up to elevation 5287 to form a wedge shape and prevent <br />erosion along the right bank. <br /> <br />Boatchute 2 was reconstructed in the model with the invert elevation at 5284.5 feet (fig. 26). <br />Boatchute 2 contained a center trough through the first ramp (the same as boatchute 1). Wave <br />patterns were excellent with a V-wave forming in the middle of the second ramp. <br /> <br />Tests were run on boatchute 2 to determine the optimum elevation of the ramps with respect to <br />the tailwater elevation. The elevation of the weir blade on the end of the model was adjusted to <br />simulate elevation changes at boatchute 3 (not modeled). <br /> <br />The fmal design modification occurred in May 1989 on boatchute 1. Using information obtained <br />from the optimization tests on boatchute 2, the elevation of the first ramp was reduced to <br />5286.75 feet, and the elevation of the second ramp was reduced to 5286.0 feet. The length of the <br />10 to 1 slope was increased to accommodate the reduction in elevation of the two ramps (figs. 3- <br />5). This modification was made to accommodate the larger drop of 3-1/2 feet at boatchute 1 <br />Boatchute 2 drop was 2-1/2 feet. The wave pallerns and boating conditions were excellent <br />throughout the boating flows. <br /> <br />Final boatchut' configuration. . After the final configuration of the boatchute was established, <br />including the low flow notch in the center and the combination of two ramps to disperse the wave, <br />a series of tests was conducted to determine the optimum elevation of the ramps with respect to <br />tailwater elevation. Figure 27 shows the optimum relationship between the ramp elevations on <br />boatchute 1, boatchute 2, and the pool between the two boatchutes. The capacity of the low flow <br />notch in boatchute 2 (elevation 5284.5 to 5286.0) is approximately 30 ff Is. For flows exceeding <br />30 ft' /s (including sluice flows), the second ramp in boatchute 1 will be completely submerged. The <br />low flow notch extends through the first ramp; therefore, smaIl boats will be able to pass through <br />the notch at low flows. As the flow increases and the pool rises, the combination of the two ramps <br />spreads the wave while maintaining a V pattern in the center. Without the low flow notch through <br />the first ramp, the wave was unifonnly dispersed in the downstream pool and the wave height was <br />reduced. However, boats tended to turn sideways as they went over the second ramp. The low flow <br />notch maintains a V-wave in the center which keeps the boats straight. Pilot rocks placed upstream <br />of and outside of the 32.foot-wide boatchute will not adversely affect flow pllllerns. However, a <br />pilot rock should not be used on the right side of boatchute 1 since space is not available in this <br />area. <br /> <br />The final design of the boatchutes was optimized for a riverflow of 500 ft' Is; 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 :t4 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 />8 <br />