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U • T-1 AND T-2 SPILLWAYS RECEvED OCT 0 2 1995 III 1111111111111111 999 5/6 Since there is a ditch above th~~,~pp$~i~REl~i~fts all surface flow away from the pond a peak flow that T-1 and T-2 will need to handle is the 70 gpm flow from the long pond or the decant flow from the 25-year event. The long pond has the capacity to decant from one 6-inch pipe at 177 gpm and two four inch pipes at 64 gpm each or 128 gpm. Design the open channel for 305 gpm + 10% = 336 gpm (0.75 cfs) OPEN CHANNEL SPILLWAY BETWEEN T-1 AND T-2 PONDS FLOW IN A TRIANGULAR CHANNEL C DEPTH D 0.550 FEET SLOPE S 0.010 EXPRESS AS DECIMAL Mannings "N" N 0.030 EXPRESS AS DECIMAL SIDE SLOPE X 1.500 SLOPE = X:1 AREA=(W*D)+(X*D^2)= WETTED PERIMETER=(W)+2((XD^2+D^2))^.5 R=AREA/WETTED PERMITER V=(1.49/N)*(R^.667)*(S^.5}= Q = A X V = Q REQUIRED 336 GPM = 0.75 CFS The spillway will be a triangular with 1,5h:1v side slopes. With a required depth of the spillway is slow enough that erosion will not SPILLWAYS BETWEEN T-2 AND OUTFACE 001 0.45 FEET^2 1.98 FEET 0.23 1.86 FEET/SEC 0.84 CFS 0.75 channel 0,55 feet deep freeboard of 1.0' the 1.55 feet. The flow velocity be a problem. DISCHARGE THOUGH A SUBMERGED TUBE DIAMETER OF PIPE AREA OF PIPE C = LOSS COEFFICIENT H = HEAD ON SPILLWAY Q = C A (2GH)^.5 Q = Q = ONE 4-INCH PIPE _ Q = TWO 4-INCH PIPES = 4.000 INCHES 0.0872 SQUARE FEET 0.500 0.167 FEET 0.1429 CUBIC FEET PER SECOND 64 GALLONS PER MINUTE 128 GALLONS PER MINUTE DISCHARGE THOUGH A SUBMERGED TUBE DIAMETER OF PIPE AREA OF PIPE C = LOSS COEFFICIENT H = HEAD ON SPILLWAY Q = C A (2GH)^.5 Q = Q = ONE 6-INCH PIPE _ 6.000 INCHES 0.1963 SQUARE FEET 0.500 0.250 FEET 0.3937 CUBIC FEET PER SECOND 177 GALLONS PER MINUTE P-9-9 09-27-95 s