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L'lt,,i;i'! �.'.fl(i �i(7iil'l1�0i1 <br /> however the Rational Rain(all Method can accommadate other removal efficiency or par:icle s�ze <br /> targels. It can also be used to estimate 2nnual hydrocarbon load reductions. <br /> Once a System size is established, the intemal etements ot the System will be designed based on <br /> inlormation provided by the site engineer. Flow control sizes and shapes, sump depth,spill storege <br /> capacity, sediment slorage volume and intet and outlel orientation are detertr�ined for each System. In <br /> addition,bypass weir caiculations are made tor off•line Systems. <br /> Flow Control Calculallons <br /> rne o.rnoe <br /> The lower(low control or"urifice"is typically si•ed to submerge lhe inlel pipe�vhen the VoAechs <br /> System is operating at 20%of its'treatment caFaciry. The orifice is typically¢�Cippoletli shaped <br /> aperture defined by its flat cresl and sides which incline outwardly al a slope of 1 honzontal to 4 <br /> vertical. <br /> ♦ Flow through orifice = G,,,� = Cd•A•(2gh)05 <br /> Whe18 Cd= Ofi6CC COf1U0CliOf1 COC(fICl8111=0.56 (basad on CONTECH Stomwaler Solulions laboratory <br /> testinp) <br /> A= Orifice flow area, Rz(wlwlated by CONTECH Stomrvaler Solullont lechniral etafl) <br /> h= Design head,(l(equal lo the Inlet pipe diameler) <br /> The minimum orifice cresl length is 3-inches and the minimum orifico height is 4-inches. If flow must be <br /> reslricted beyond what can be provided by this size aperture,a Fluidic-AmpT"' hydro-brake ilow control <br /> will be used. The hydro-brake allows the minimum Ilow constriction to remain at 3•inches o:greater <br /> while further reducing ilow due to its unique throtlling action. <br /> The Welr <br /> The high flow conlrol or'1vei�'is sizecl to pass lhe peak System capacity minus the peak orifice tlow <br /> when the water suAace elevation is at the top of lhe weic This flow condol is also a Cippoletti rype <br /> weir. <br /> 1'he weir flow control is sized by solvinp for the crest length and head in the following equation: <br /> ♦ Flow lhrough weir= Q„�„ = cd•L•(h)�° <br /> Where Cd= CippOlelH Weir coeffiCient= 3.37 @asetl on CONTECH Stormwatar sowtions laboremry�asang� <br /> h= Available head, ft�neiBm oi we��� <br /> L= Design weir Crest lenglh, fl(calculaiotl hy CONTECH Stormwaler Solutions technical statQ <br /> Bypass Calculations <br /> In some cases, pollutant removal goals can be met without treating peak flow rates and il is most <br /> feasible lo use a smaller Vortechs System confi�ured wilh an external bypass. In such cases,a bypass <br /> design is recommendeA by CONTECH Stormwater Solu�ions for each off-line System.To calculate Ihe <br /> bypass capacity, first subtract ihe System's treatment capacity irom the peak conveyance capacity of <br /> the collection system(minimum ot 10 year recurrence interval).The result is lhe flow rate lhat must be <br /> bypassed to avoid surcharging the Vortechs System. Then use lhe following arrangement of the <br /> Francis fortnula to ca�culale the deplh of tlow over the bypass weir. <br /> y Flow over bypass weir = II = (Qh���,, iC�•I.11' ' <br /> Where <br /> Ca = Discharge Coefficient= 3.3 for rectar.gular weir <br /> H = Depth ol flow over bypass weir c�est, 9 <br /> L = Length ol bypass weir cresl, ft <br /> The bypass weir crest elevalion is lhen calculateA to be the elevation at the top of liie Cippoletti weir <br /> m�nus the depth of flow. <br /> �%2006 CONTECH Stormwa�er SoWlions 115 <br />