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1 <br /> �OROUP FOUR� INC� � 5=10-89 �11 �25AM �EVERETT WA PBLC WRNS� 2083623818�� � �i <br /> � 4. 3.15. 8 Other design criteria fox gxass lined sw3les: <br /> a) 25 year design storm <br /> b) mzx3mum vslocity of #our feet per second using <br /> Mannings Equation with h=.035 <br /> e) Maximum flow depth of 5.4 znches. <br /> d) Maximum side slopa of three horizontal to ana <br /> vertical <br /> e) Longitudinal slope no greatez than 5 percent <br /> f) Minimum freeboard oP six inches <br /> , Add: <br /> 4.3.16 UTL/WATER SEPARATION AND GRTT REMOVAL <br /> a.3 .16. 1 For Stormwa�er t�eacment the vaul� �hall provide a <br /> mihimum oP a 15 minute retention time at �he rate of <br /> the vault inlet capacity. <br /> 4. 3.16.2 For Stormwater �Yeatment the vault inlet aapacity <br /> shall bo detarmined by use o� the rational formula, <br /> Q = cia. 'Phe intensity for uge in the rational <br /> formula shall be 0.5 in/hx <br /> 4 .3 .16. 3 For Stormwatier txeatment a bypass piping systam <br /> shall be used to divext axaesa flow axouttd the vault <br /> when the inflaw rate eXCeeds the capacity of the <br /> vaul� inlet. <br /> 4 . 3 .16.4 For spi11 containment, vault� shall be equipped with <br /> an isolation valve. <br /> 4 .3. 16.5 Spill containment vaults shall discharga £rito the <br /> sanitarp sewer system. <br /> 9 .3 . 16. 6 Spill containment vaults shal� provide a minimum <br /> "live" capaoity of 2500 gallons. <br /> 4-3 . 16.7 Bypass piping shall not be allowed Por spi�l <br /> containment vaults. <br /> 4.3 . 16.8 CoeZescing plates may be required for sites with a <br /> high risk of large volume spills or disnharges. <br /> Change: <br /> 4 . 3 .1a INFILTRATION SX5TEMS to read: - <br /> Infiltration systems are generally not recommended <br /> as the sole m�ans of disposinq of Stormwater. <br /> However, fnfi�tration systeras designed to inEiltratQ <br /> small storms attd the first flush of large storms <br /> while safely ovenflowing large storm events to an <br /> established drainage aourse are recommended as a � <br /> means of �reat�ng stormwater. <br /> 4.3. 10.1 011/Water separat3on and grit removal in accordance <br /> with sect�on 4.3. 16 will be required upstream of all <br /> inEiltratSon systems. Alternatively a wet pond <br /> could be uwed to remove oil and sediment prior to <br /> d�scharging to zhe infiltration syatem. <br />