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CITY OF EVERETf STORMWATER MANAGEMENi MANUAL <br /> � <br /> ! Conditionso/Use <br /> Wtiere the cunoff from an exposed site or dishubed slope must be cor�veyed to an erosion conRol (acility <br /> which can safcly conUin the srortnwatcr. <br /> 1. Locate upslopr.of a construction site to prevent runoff from entcring disturbed area <br /> 2. When placed horiwntally across a disnubed slope,it reduccs the amount and velocity of runoft <br /> flowing down thc slope <br /> 3. Locete downslopc to collect runoff Gom a disturbed area and direct it to a sediment bazin. <br /> Design and Installation Speei/icaduns <br /> 1. Dike and/or swale and chennel must be stabilized with temporary or pecmanent vegetation or <br /> other r,hannel protection during construction. <br /> 2. Channel requires a positive grade for drainage;steeper grades requirc channel protcction and <br /> check dams <br /> 3. Revicw conshuction for areas where overtopping may occur <br /> 4. Can be used at top of new fill before vegetation is established <br /> 5. May be used as a permanent diversion chennel to carry the mnoff <br /> 6. Subbasin tributary arca should be 1 acrc or Icss <br /> 7. Design capacity for the peak tlow from a l0-year,24-hour storm,assumiag a Typc I A rainCali <br /> distribution, for temporary facilities. Altematively,use I.G dmes the 10•year, I-hour time step <br /> 1 flow indicated by an approved continuous runoff modcl. lf a l5•minute(or less)time step is <br /> � used,no co�rection facror is required. <br /> 8. Interceptor dikes sha!I meet lhe following critcria: <br /> a. Top Widt6 = 2 feat minimum <br /> b. Height = I.5 feet minimum on bcrm <br /> c. Side Slopa = 2:1 or flattcr <br /> d. Gradc = Depends on topography,howcvcr, dikc system minimum is 0.5 percent, <br /> maximum is 1 percent <br /> c. Compaction = Minimum of 90 percent AS'fM D69B standerd proctor <br /> f. Horizontal Spacing of Interceptor Dikes: <br /> Avenge Slope Slope% Flowpalh Length <br /> 20H:1 V or less 3•5% 300(eet <br /> (10 to 2D)H:1V 5-10°/a 200(eet <br /> (4to 10)H:1V 10•25% t00feet <br /> (2 to 4)H:1V 25-50% 50 feet <br /> g. Stabilizalian depends on velociry and reach: <br /> o Slvpes ic^.e fh�.n 5 percenr. Seed and mulch applied within 5 days of dike <br /> conswction(sce BMP Clll, Mulching). <br /> Volume II—Construction Stormwater Pollution Prevention <br /> 3-36 <br />