When there is heavy rainfall during storms, the runoff, especially in built-up areas will be heavy, as there is little or no absorption of the rain as it falls. This can cause flooding and lead to bodies of water to which the runoff drains, getting polluted due to the debris and dirt that the runoff would contain. This can be avoided if arrangments are made to control the runoff and allow it to reach water bodies in a more controlled manner. One such arrangement is the installation of stormwater chamber systems that can control as well as filter the flow of water, so as to reduce the pollution in natural water bodies, to which the runoff must at some stage, find its way.
Above ground systems make the use of dry or wet ponds near the area whose runoff needs to be controlled and act to retain the water and allow it to drain out to natural water bodies in a controlled manner. A wet pond will always have a constant depth of water, and only when its control level is exceeded will the water be allowed to flow out. In dry ponds, the water is allowed to soak into the soil, while the retained water allows settlement of dirt and debris, and only when the capacity of the pond is reached, that it will be allowed to overflow into water bodies. Above ground systems for stormwater management require a lot of area that is then made unusable or development.
Underground systems create concrete vaults, pipe chambers, or other structures that can retain a finite amount of water. Once this capacity is reached, the water is allowed to overflow to water bodies or natural drains. The capacity of such built-up stormwater chamber systems has to be determined as per the area being served and the maximum intensity of rainfall expected in that geographical area. These can often be quite substantial and involve capital costs. These costs have to be weighed against the fact, that these underground structures allow for land development above to create parking lots, playgrounds and other amenities that the project may require and help to mitigate costs. Such underground chambers require proper maintenance to ensure that the built up capacity remains completely usable when it is needed. Often such chambers are built to retain the water, while its floors and side walls will allow infiltration into the surrounding soil so that the water is absorbed.
The decision on building the right structure for the stormwater chambers will depend on a proper investigation of the soil in which they are built. Sandy soils will allow easy infiltration and are ideal, while clayey soils tend to retain water and may need other technical attention.
The location of the property for which stormwater management systems can determine the type of systems that will be more efficient in controlling stormwater and preventing flooding. If the area is near an existing natural body of water, a detention system is a better system than a system that depends on infiltration.
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