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OUTFALL PROTECTION DESIGN <br /> FOR MOUNTAIN VIEW BUSINESS CENTER DIVISION 9: LOTS 1-3 <br /> INFILTRATION BASIN <br /> Western Washington Hydrology Manual(WWHM2012 output) <br /> 100-Year Unmitigated Flow=Q=17.6 cfs <br /> Q1/2=Q/2=8.8 cfs(for each 12" diameter pipe) <br /> U.S. Department of Transportation:Hydraulic Design of Energy Dissipators for Culverts and Channels <br /> (Hydraulic Engineering Circular No. 14, Third Edition). <br /> 10.2: RIPRAP APRON <br /> L1 - <br /> 4/3fDlDso = 0.2D 32.2D <br /> * 2.5] 1.TW1 <br /> D50=riprap size,ft(50%finer by weight) <br /> Q=design discharge,cfs <br /> D= pipe diameter,ft <br /> TW=Tailwater depth,ft(assume 0.4D for unknown conditions) <br /> Q1/2=8.8 cfs <br /> D=1ft <br /> TW=0.4ft �� 3.• N'0 <br /> Yields, Dso=0.89 ft(10 inch Riprap Diameter) 7ir <br /> Table 10.1: Riprap Classes and Apron Dimensions so 54301 X' <br /> Class 3 Riprap: ' /1 ' h ONAL Y <br /> D50= 10in <br /> Apron Length=5D=5 x 1ft=5 feet <br /> Apron Depth,2.4Dso=2.4 x 0.89=2 feet <br /> Proposed Design: <br /> Two 12"diameter parallel pipes discharging to infiltration basin <br /> Riprap Apron: 10' Long x 8'Wide x 2' Deep <br /> Use 8"-12" Diameter Riprap (50% passing 10"sieve gradation) <br /> Construct 1'deep riprap settling basin for additional protection due to slope of inlet pipe) <br />