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<br />2 <br /> <br />half of the crest to understand the difference in flow patterns. Those in attendence <br /> <br /> <br />agreed that the flow patterns over the crest were much improved for a large range <br /> <br /> <br />of flows with the sl11 in place. <br /> <br />To illustrate the difference in the performance of the upstream and downstream <br /> <br /> <br />boatchutes, the downstream boatchute was used with a wide crest width of 64 feet. <br /> <br /> <br />The upstream chute at the existing USACE dam has a crest width of 32 feet, then a <br /> <br /> <br />narrowing to 20 feet Ina length of 20 feet. It was noted by David Walker and others <br /> <br /> <br />that the flow patterns in the downstream chute were less desirable than those in the <br /> <br /> <br />\lpstream chute. The concensus of the group was to make the dimensions of both <br /> <br /> <br />chutes the same, I.e., using a crest width of 32 feet. <br /> <br />At flows ot 300 cts to 800 cts, the central wave In the upstream boatchute was about <br /> <br />1.0 to 1.5 teet high. Scott Tucker, Ben Urbonas, and Mark Hunter of the UDFCD were <br /> <br />concerned that this would give boaters a jolt. They recommended using a sill simi- <br /> <br />lar to that mentioned above. Ben found a small, flat board and Inserted it into the <br /> <br />flow to determine its effect on the flow patterns in the upstream boatchute. There <br /> <br />was a marked decrease In the height of the wave. The best position for the sill <br /> <br />appeared to be immediately downstream of the rocks which narrowed the chute <br /> <br />width to 20 feet. Cliff Pugh of the USBR commented on the need to maintain the spe- <br /> <br />cified low flow notch in the chute if a sill was selected. <br /> <br />The nominal elevation of the boatchute at the USACE dam is 5088.75 while the nomi- <br /> <br />nal elevation of the boatchute at the downstream embankment crest is 5085.0. <br />