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1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />�i <br />1 <br />1 <br />LJ <br />1 <br />1 <br />1 <br />Stone for riprap shall consist of field stone or quarry stone of approximately rect- <br />angular shape. The stone shall be hard and angular and of such quality that it will <br />not disintegrate on exposure to water or weathering and it shall be suitable in all <br />respects for the purpose intended. <br />A lining of engineering filter fabric (geotextile) shall be placed between the riprap <br />and the underlying soil surface to prevent soil movement into or through the riprap. <br />The geotextile should be keyed in at the top of the bank. <br />. Filter fabric shall not be used on slopes greater than 1-1/21­1:1 V as slippage may <br />occur. It should be used in conjunction with a layer of coarse aggregate (granular <br />filter blanket) when the riprap to be placed is 12 inches and larger. <br />BMP C203: Water Bars <br />Purpose <br />A small ditch or ridge of material is constructed diagonally across a road or right-of-way <br />to divert stormwater runoff from the road surface, wheel tracks, or a shallow road ditch. <br />See Figure II-4.2.3 Water Bar (p.341). <br />Conditions of Use <br />Clearing right-of-way and construction of access for power lines, pipelines, and other <br />similar installations often require long narrow right-of-ways over sloping terrain. Dis- <br />turbance and compaction promotes gully formation in these cleared strips by increasing <br />the volume and velocity of runoff. Gully formation may be especially severe in tire tracks <br />and ruts. To prevent gullying, runoff can often be diverted across the width of the right-of- <br />way to undisturbed areas by using small predesigned diversions. <br />Give special consideration to each individual outlet area, as well as to the cumu- <br />lative effect of added diversions. Use gravel to stabilize the diversion where sig- <br />nificant vehicular traffic is anticipated. <br />Design and Installation Specifications <br />. Height: 8-inch minimum measured from the channel bottom to the ridge top. <br />• Side slope of channel: 2H:1 V maximum; 3H:1 V or flatter when vehicles will cross. <br />Base width of ridge: 6-inch minimum. <br />. Locate them to use natural drainage systems and to discharge into well vegetated <br />stable areas. <br />• Guideline for Spacing: <br />2014 Stormwater Management Manual for Westem Washington <br />Volume 11 - Chapter 4 - Page 339 <br />