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Chapter 4 - Best Management Practices for Erosion and Sediment Control <br /> 4. 15 TEMPORARY DIVERSION DIKE <br /> (ES BMP 1 . 15) <br /> Definition <br /> A temporary ridge of compacted soil located at the top or base of a sloping disturbed area . <br /> Purposes <br /> 1 . To divert storm runoff from higher drainage areas away from unprotected slopes to <br /> a stabilized outlet. <br /> r <br /> 2 . To divert sediment-laden runoff from a disturbed area to a sediment trapping <br /> facility . <br /> Condition Where Practice Applies <br /> Wherever stormwater runoff must be temporarily diverted to protect disturbed slopes or <br /> retain sediments on site during construction . These structures generally have a life <br /> expectancy of 18 months or less . <br /> Planning Considerations <br /> A temporary diversion dike is intended to divert overland sheet flow to a stabilized outlet or <br /> a sediment trapping facility during establishment of permanent stabilization on sloping , <br /> disturbed areas . When used at the top of a slope , the structure protects exposed slopes <br /> by keeping upland runoff away. When used at the base of a slope , the structure protects <br /> adjacent and downstream areas by diverting sediment-laden runoff to a sediment trapping <br /> facility. <br /> If the dike is going to remain in place for longer than 30 days , it is very important that it be <br /> established with temporary or permanent vegetation . The slope behind the dike is also an <br /> important consideration . The dike must have a positive grade to assure drainage, but if the <br /> slope is too great, precautions must be taken to prevent erosion due to high velocity flow <br /> behind the dike . <br /> This practice is considered an economical one because it uses material available on the <br /> site and can usually be constructed with equipment needed for site grading . The useful life <br /> of the practice can be extended by stabilizing the dike with vegetation . <br /> As specified herein , this practice is intended to be temporary. However, with more <br /> stringent design criteria , it can be made permanent in accordance with DIVERSIONS - <br /> Section 5 . 18 (ES BMP 1 . 18) . <br /> 4-55 <br />