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<br />I <br /> <br />~ <br />I <br /> <br />5.4 Chapter 5: InHltrationTrenches <br /> <br />I <br /> <br />DESIGN l: <br /> <br />I <br /> <br />Median Strip DesiKD (Figure 5.2), This design is frequently used <br />for highway median strips and parking 101: "islands" (depressions <br />in between two lots or adjacent sides of one lot). Sheet flow is <br />accepted from both sides of the trench, and is filtered through a <br />20 foot wid. grassed buffer strip. The strip is an integral part <br />of the trenc.hJ and should be graded to have a uniform slope not <br />greater than 51, and should directly abut the contributing <br />impervious ares. Berms located on each side of the strIp form a <br />shallow depression that temporarily stores runoff before it enters <br />the trench. An overflow pipe is used to pass excess runoff. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />Figure 5.2: <br /> <br />Median Strip Trench Design <br /> <br />I <br /> <br />Top View <br /> <br />Side View <br /> <br />. <br /> <br />~fi~~z;~l~~tlf <br /> <br /><-1"'0' '.'.'... <br /> <br />Inflow <br /> <br />I <br /> <br /> <br /> <br />20" Grasa Flit., Stl1p <br /> <br />--.... <br /> <br />I <br /> <br /> <br />Permeable Filter <br />Fabric: One Fool <br />Below Sur1ac~. <br />Traps Debris <br /> <br />I <br />Sides lined.with P~rmeable Filtel Fabric <br />, <br />, <br />Clean Washed Slone or Gravel <br />(':.5-3.0 tneh' <br />'6-12 Inch Sand Filtel <br />01 Permeable Filter <br />Cloth Lines Bottom <br /> <br />I <br /> <br />I <br /> <br />Screened Overflow Pipe <br /> <br />I <br /> <br />J?~'i~L.. ";"""'~""""' <br />1~~~~Ii:"..".:;',:;;;;:; <br /> <br />-- <br />Outflow <br /> <br />I <br /> <br /> <br />I <br />