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• PRINCIPAL SPILLWAY <br />t <br />• ~ <br />~~ <br />The principal spillway ~vi11 consist of a 36 inch diameter decant or <br />riser pipe appro:timately 17.8 feet high. In order to allow closure of the <br />decant, an Armco 20-lOC will be installed at the inlet, The gate will <br />be controlled from the too of the dam via a lift station and an encased <br />turn stem. The decant cvill b e equipped with a trash rack and an <br />anti-vorte:c baffle plate. The decant pipe vrill enter a "T" connection <br />where it v~ill drain into a 36 inch diameter pipe appro:tir..ately 147.6 <br />feet long. At the end of the drain pine will be 50 feet of rip-rap <br />forming a basin to eliminate erosion of the embankment. At the upstream <br />section of the aferementior,ed "T" connection will be .a reduction section. <br />The reduction section will be appro:~imately eight feet long and reduce <br />36 inch diameter to a 24 inch diame*_er. The 24 inch*!'iameter pipe <br />leaving the reduction section cvill be approximately 50.7 feet long and <br />will go to a drainage gate. <br />The drainage gate will be an Armco 50-lOC and will be mounted in a <br />concrete basin complete with trash racks. Both the 50-lOC and the <br />20-lOC will be operated from the embankment crest by oil filled stems <br />supported on concrete anchcr blocks. Each lift stem will be turned <br />at the lift station with a gear reduced turning stem and crank. <br />All pipe installed for the principal spillway will be 14 gauge, 2-2/3 <br />inch by 1/2 inch corrugated. annular pipe. Each joint of pipe will <br />have rolled ends to accommodate a watertight one-piece coupling with <br />"O" ring seals placed on each side of the connection. All pipe and <br />connections will be asphalt coated. <br />The principal spillway will also be ecuinped with faur 96 inch by 96 <br />inch anti-seep diaphrams. The diaphrams will be 14 gauge corrugated metal <br />and they will be asphalt coated. <br />Weighted creep factcr along principal spillway pipe = 2.85. <br />Flow capacities of the principal spillway are as foLows: <br />36" Decant Capacity: <br />Q = C1IDH1.5 <br />C = 3.22+0.44 H/P <br />P =Height of Inlet <br />H =Hydraulic head. <br />- 5 - <br />._ REVlSEd. .FEB 1 3-'~.- <br />