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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br /> <br />Mr. Nick Ioannides <br />April 24, 1986 <br />Page 3 <br /> <br />2. A backhoe was moved onto the site to arrange the Boul ders into the <br />planned configuration (see Photo 2). This work was accomplished in <br />one day during low flow and was inspected at night during high flow <br />from the Boulder Canyon hydroelectric plant. Minor modifications <br />were then made the following day. <br /> <br />3. After blocking the flow and pumping it around the site, the entire <br />area was grouted into pl ace. Aggregate (3/4-inch diameter) grout was <br />pumped by hose into the voids in the rock, then hand-troweled into <br />pl ace. The center channel was made smooth with protruding smooth <br />cobbles, and the bank and deflectors were constructed of large (two- <br />to three-foot) stones approximately half-buried into the grout. (See <br />Photo 3.) <br /> <br />4. The stones were then washed off and the fast-sett i ng grout was a 1- <br />lowed to set before the evening water release. The area was cleaned <br />up and equi pment removed. <br /> <br />Analys i s <br /> <br />An as-built plan and profile drawing is shown in Figure 2. Notice the rela- <br />tively smooth sloping face down the center of the chute and the offset de- <br />flectors along the edges. The downstream base was built onto protruding <br />shale bedrock. Photos 4 and 5 show the chute with a flow of approximately <br />80 cfs and 180 cfs, respectively. <br /> <br />For the range of flows, including the higher and lower flows, the chute <br />functions quite well. Due to the offset deflector design, no linear holes <br />or keepers appear at the base of the chute. Di agonal waves form within the <br />chute giving it smooth, whitewater wave characteristics. A small "hole" or <br />"backwash" forms at higher flows near the entrance of the chute near the <br />river right bank. This could be eliminated by extending the right deflector <br />upstream farther with a gr adua 1 curve, s imil ar to the 1 eft defl ector. A" V" <br />cross section at the entrance would also be desirable, but was not possible <br />due to the ex i st i ng sewer 1 i ne. <br /> <br />Overall, the drop is navigable for most intermediate boaters, including <br />small rafts, canoes, and kayaks, but is somewhat intimidating due to the <br />total vertical drop of four feet. <br /> <br />For larger rivers and for drops designed for the low-intermediate to begin- <br />ner boater, we recommend this similar design, but for not over a two-foot <br />vertical drop. This should reduce the turbulence at higher flows and allow <br />the boater to inspect the entire drop from the boat. <br /> <br />KRW/RAF:djg <br />831-036.060 <br />Attachments <br />