Laserfiche WebLink
0 • <br />Chapter 4-Site-Specific Industrial Storm Water BMPs <br />Paved chutes may be covered with a surface of concrete or other impenetrable material. <br />Subsurface drains can be constructed of concrete, PVC, clay tile, corrugated metal, or other <br />permanent material. <br />What to Consider <br />The drain design should be able to handle the volume of flow. The effective life span of a <br />temporary pipe slope drain is up to 30 days after permanent stabilization has been achieved. The <br />maximum recommended drainage area for pipe slope drains is 10 acres (Washington State, 1992). <br />The inlets and outlets of a pipe slope drain should be stabilized. This means that a flared end <br />section should be used at the entrance of the pipe. The soil around the pipe entrance should be <br />fully compacted. The soil at the discharge end of the pipe should be stabilized with riprap (a <br />combination of large stones, cobbles, and boulders). The riprap should be placed along the bottom <br />of a swale which leads to a sediment trapping structure or another stabilized area. <br />Pipe slope drains should be inspected on a regular schedule and after any major storm. Be sure <br />that the inlet from the pipe is properly installed to prevent bypassing the inlet and undercutting the <br />structure. If necessary, install a headwall, riprap, or sandbags around the inlet. Check the outlet <br />point for erosion and check the pipe for breaks or clogs. Install outlet protection if needed and <br />promptly clear breaks and clogs. <br />Advantages of Pipe Slope Drains <br />• Can reduce or eliminate erosion by transporting runoff down steep slopes or by draining <br />saturated soils <br />• Are easy to install and require little maintenance <br />Disadvantages of Pipe Slope Drains <br />• Require that the area disturbed by the installation of the drain should be stabilized or it, <br />too, will be subject to erosion <br />• May clog during a large storm <br />4-73