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9 Chapter 4-Site-Specie Industrial Storm Water BMPs <br />tank truck compartment. Materials used to construct the dike should be strong enough to safely <br />hold spilled materials. The materials used usually depend on what is available onsite and the <br />substance to be contained, and may consist of earth (i.e., soil or clay), concrete, synthetic <br />materials (liners), metal, or other impervious materials. In general, strong acids and bases may <br />react with metal containers, concrete, and some plastics, so where spills may consist of these <br />substances, other alternatives should be considered. Some of the more reactive organic chemicals <br />may also need to be contained with special liners. If there are any questions about storing <br />chemicals in certain dikes because of their construction materials, refer to the Material Safety Data <br />Sheets (MSDSs). <br />Containment dikes may need to be designed with impervious materials to prevent leaking or <br />contamination of storm water, surface, and ground water supplies. <br />Similarly, uncontrolled overflows from diked areas containing spilled materials or contaminated <br />storm water should be prevented to protect nearby surface waters or ground waters. Therefore, <br />dikes should have either pumping systems (see Sumps BMP) or vacuum trucks available to remove <br />the spilled materials. When evaluating the performance of the containment system, you should pay <br />special attention to the overflow system, since it is often the source of uncontrolled leaks. If <br />overflow systems do not exist, accumulated storm water should be released periodically. <br />Contaminated storm water should be treated prior to release. Mechanical parts, such as pumps or <br />even manual systems (e.g., slide gates, stopcock valves), may require regular cleaning and <br />maintenance. <br />When considering containment diking as a BMP, you should consult local authorities about any <br />regulations governing construction of such structures to comply with local and State requirements. <br />Facilities located in a flood plain should contact their local flood control authority to ensure that <br />construction of the dikes is permitted. <br />Inspections of containment dikes should be conducted during or after significant storms or spills to <br />check for washouts or overflows. In addition, regular checks of containment dikes (i.e., testing to <br />ensure that dikes are capable of holding spills) is recommended. Soil dikes may need to be <br />inspected on a more frequent basis. <br />• <br />Changes in vegetation, inability of the structure to retain storm water dike erosion, or soggy areas <br />indicate problems with the dike's structure. Damaged areas should be patched and stabilized <br />immediately, where necessary. Earthen dikes may require special maintenance of vegetation, such <br />as mowing and irrigation. <br />Advantages of Containment Diking <br />• Contains spills, leaks, and other releases and prevent them from flowing into runoff <br />conveyances, nearby streams, or underground water supplies <br />• Permits materials collected in dikes to be recycled <br />• Is a common industry practice for storage tanks and already required for certain chemicals <br />Disadvantages of Containment Diking <br />• May be too expensive for some smaller facilities <br />• Requires maintenance <br />• Could collect contaminated storm water, possibly resulting in infiltration of storm water to <br />ground water <br />4-13