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<br />passageways that are closed by gates. Occasionally, a structure <br />will have a floodwall incorporated into the architectural design. <br />The use of levees and flood walls will usually require a sump <br />pump system to evacuate internal drainage along with under- <br />seepage that might occur. Excessive underseepage from <br />improper design is a common problem. <br /> <br />Closures and sealants <br /> <br />Plastic, marine paints and water proofing compounds, and <br />other sealants can be applied to structures, provided the <br />structure can withstand the hydrostatic and hydrodynamic <br />pressures. In addition, the foundation must be designed to <br />withstand uplift forces caused by water pressure beneath the <br />structure. A variety of bulkhead designs are used ranging from <br />single plywood sheets to expensive steel stoplogs. It is extremely <br />difficult to make closures completely watertight, and many <br />systems using this technique employ pumps to evacuate leakage. <br />No attempts should be made to seal a structure against floods <br />deeper than 2 to 3 feet until the structure has been examined by <br />a qualified professional engineer to determine that it can <br />withstand the increased hydrostatic loads. <br /> <br />Other flood proofing <br /> <br />efforts <br /> <br />A few other flood proofing techniques which do not fit the <br />above categories have been developed. One of these is known as <br />wet flood proofing. With this technique, the structure is built of <br />materials that are not easily damaged by flood waters and can be <br />easily cleaned following a flood. Such materials include exterior <br />or marine plywood. Often the structure is allowed to fill with <br />clean water to minimize damage. This is also done to prevent <br />the structure from collapsing from hydrostatic loading. In some <br />areas, new construction behind low-frequency protection levees <br />has utilized wet flood proofing on a large scale. The technique <br />can be particularly useful to industries and businesses in <br />reducing flood damages. Another technique that is rarely seen is <br />to build the structure on pontoons or a barge-type foundation <br />such that the structure floats during the flood. In this case, all <br />land-based supporting facilities, utilities, etc., have flexible line <br />connections. Other methods, such as wrapping the house in <br />plastic or rubber sheeting, have also proven to be successful. <br /> <br />More detailed informationon each of these flood proofing <br />techniques is found in Appendix A. <br /> <br />8 <br /> <br />I <br />.... <br />