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<br />Chapter 4-Site-Specific Industrial Storm Water BMPs <br />L? <br />What Are They <br />Diversion dikes or berms are structures used to block runoff from passing beyond a certain point. <br />Temporary dikes are usually made with compacted soil. More permanent ridges are constructed <br />out of concrete, asphalt, or similar materials. <br /> <br />?J <br />?r <br />/ r <br />Dike <br />FIGURE 4.2 DIVERSION DIKES <br />(Modified from North Carolina, 1988) <br />When and Where to Use Them <br />Diversion dikes are used to prevent the flow of storm water runoff onto industrial areas. Limiting <br />the volume of flow across industrial areas reduces the volume of storm water that may carry <br />pollutants from the area, requiring treatment for pollutant removal. This BMP is suitable for <br />industrial sites where significant volumes of storm water runoff tend to flow onto active industrial <br />areas. Typically, dikes are built on slopes just uphill from an industrial area together with some sort <br />of a conveyance such as a swale. The storm water conveyance is necessary to direct the water <br />away from the dike so that the water will not pool and seep through the dike. <br />What to Consider <br />In planning for the installation of dikes, consider the slope of the drainage area, the height of the <br />dike, the size of rainfall event it will need to divert, and the type of conveyance that will be used <br />with the dike. Steeper slopes result in higher volumes of runoff and higher velocities; therefore, <br />the dike must be constructed to handle this situation. Remember that dikes are limited in their <br />ability to manage large volumes of runoff. <br />4-7