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�SECf10N 53 DE7E`7770\FACLLITIES �hee f 2 oF Z <br /> f - <br /> 5.3.1.2 METHODS OF ANALYSIS <br /> 1 Detention Volume and Outflo�r <br /> I 7'he volume and outflow design for deewtion ponds shsll be in accordance with the performance <br /> requirements in Chapter 1 and the hydrologic analysis and design methods in Chapter 3. Restrietor orif ce <br /> structure daign shall comply with Scction 53.4(p.5-40). Note: The destgn wa�er surface elevalion is <br /> I the higkesr elevarion whrch occurs in ordt�ro meet the required o�uflow perfomwnce for rhe pond. <br /> Detention Ponds in Infiltrative Sofls <br /> � Detention ponds may occasionally be sited on till soils that othenvise meet the basic criteria of"sufticient <br /> permeable soil"for a properly functioning infilvation system(see Sation 5.4.1,p.5-53). These detencion <br /> ponds have a surface discharge and mzy also utilize infilvation as a second pond outflow�. Detention ponds <br /> I sizzd with infiltration as a secon( outflow must meet all the requiremmt;of Sation 5.4 for infilvuion <br /> ponds,including a soils report,cesting,¢rounda•ater proteetion,presettling,and construction tahniques. <br /> I Emergency Overflow Spillway Capacity <br /> The emergency overflow spillway w'eir sation shall be designed to pass the ]00-y�.ar runoff event for <br /> developed condi[ions assuming a broadtrested aeir. The broad•crated�r•eir equation for the spilh�•ay <br /> Iseciion in Figure 53.I.E,for example,«•ould be: <br /> Qioo = �('-8)�R I�h LH�+9hs(Tan 6)Ns"'J (5'�) <br /> l where Qioo = pea}:flow for[he 100-year runoff e�•rn�(fps) <br /> C = discharge eafficien�(0.6) <br /> I 8 = graviry(33.2 fdsec'') <br /> L = length of weir(fQ <br /> y = height of water o�•er��•eir((Q � <br /> I B = anglo of side slopes <br /> Assuming C=0.6 and Tan 0=3(for 3:1 slopes),the equa�ion becomes: <br /> 1 Qioo = 3•'-� (�y�+2.4Ns") (5�2) <br /> I To fin 1��•idth L for the weir section,the equation is rearranged to use the computed Qioo a�d triat vdues <br /> � of H(0.2 feet minimum): <br /> � L = IQioo/(3?� y`�)I-2.4 N or 6 feet minimum �s'3� <br /> IFIGURE 5.3.1.E �YE1R SECTION FOR EAtERGE:\CY OVERFLOIV SPILL\VAY <br /> I emergencyoverflow o.�•�d owAlow <br /> water sudace water <br /> os m��. , surlaca <br /> � e i � , � or�e. H <br /> � <br /> II • perTable4.4.tA <br /> ( � L <br /> r 9/1/96 1998 Surface\Vatet Desitn M�m+� <br /> I $ 3� � <br />