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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 />I <br />I <br />I <br /> <br />the floor will probably be bonded to resist sliding due to the drag force exerted by the flow <br />of water. Side walls ofRCC sloping back at 0.8: I slopes will be formed by the successive <br />placement of layers of RCC up to the top of the dam, or parapet wall if used. Riprap on a <br />granular bedding would be placed to protect the approach section of the spillway excavation <br />from erosion. Grading and riprap/bedding of the upstream face of the dam would be <br />performed to create satisfactory hydraulic approach conditions. A fuse plug/maintenance <br />road will be constructed on the spillway crest to cause floods of less than one in one hundred <br />year recurrence to be carried in the existing spillway.. <br /> <br />. <br /> <br />A roller compacted concrete chute section will be constructed in an excavation on the face <br />of the dam. The stepped chute will be formed by placement of horizontal layers ofRCC in <br />eight to nine foot widths, one foot thick. Each layer will be set 2'-3" back from the previous <br />layer to form a 2.25: I stepped spillway. Training walls ofRCC approximately six to eight <br />feet in height, measured normal to the slope, and sloped at 0.8: I will be formed integrally <br />with the chute by placement of successive layers of RCC. A graded gravel filter drain with <br />collection pipes underneath the concrete c1tute will be installed to provide positive drainage. <br />Backfill may be placed in the new RCC chute section to provide a maintenance road for <br />access to the dam crest. During a large discharge over the spillway the backfill material will <br />be eroded out of the channel <br /> <br />. <br /> <br />A roller compacted concrete stilling basin will be provided at the bottom of the RCC chute <br />and will be constructed integrally with me chute and training walls. A cutoff wall will be <br />constructed at the downstream end of the ,tilling basin to prevent undercutting of the basin <br />under design flows. The cutoff wall would be necessary because downstream improvements <br />to prevent channel erosion, such as riprap, would have be constructed on property owned by <br />others. It is anticipated that the cutoff wall will be constructed of drilled concrete caissons <br />or driven piles, taken down to sound bedrock, to prevent damage from local scour <br />downstream of the stilling basin. <br /> <br />19 <br />