The underground Storm Water Detention and Retention systems are today a key component of the latest site developments. The stormwater detention and retention systems come in either above-ground ponds or in the form of subsurface piping. The above-ground pond is an inexpensive method, yet it is also the least inefficient when it comes to using developable land. It is also susceptible to early clogging and siltation and poses aesthetic issues over the long-term like refuse issues, odor, weed growth, and insect breeding.
In comparison, the underground water retention as well as detention systems, use the available land far more efficiently. At the same time, they introduce lower maintenance costs and pose no or little aesthetic problems.
The detention systems are used on sites in order to lower the stormwater quantity runoff, which leaves the site in the way of storing this runoff temporarily which exceeds the allowable discharge rates of the site and then releases this water gradually over time.
Infiltration systems are also implemented to decrease the stormwater runoff volume that is being discharged from the site. The runoff strategy forms a primary part of the low-impact development designs.
The stormwater retention systems are different from the detention solutions as is allows water to discharge slowly into the surrounding soil rather than detaining the water over a period of time before releasing it.
The components of such systems usually involve an underground tank, contained pipe-systems, or arches, which are combined with aggregate layers, filters, and geo-fabrics. These systems are all designed to assist with preventing flooding which results in erosion which is the typical result of excess runoff.
With these integrated filtration components, it is now possible to ensure that discharged water is not going to have adverse effects on surrounding wetlands, rivers, streams, and aquatic life.
More About Above-Ground And Underground Water Retention Systems
Unlike the dry detention pond, the retention pond holds permanent water pool and is known as a wet pond. Typically, the retention ponds are built due to high groundwater tables. This means that the groundwater in an area is closer to the earth’s surface. The bottom of these ponds is excavated below these water table elevations in order to establish permanent pools. The outlet of these ponds is positioned either above or at the desired elevation of the pool.
The underground retention systems are usually constructed out of steel, plastic materials, or concrete. Each of these materials is associated with its own set of benefits and drawbacks, along with specific applicabilities.
The underground retention system is mainly used in areas that are newly-developed where land availability or costs are the main concern. These systems are generally built under paved surfaces and parking lots in residential, industrial, or commercial areas. The perforated underground system which is designed to release the stored stormwater into the soil is only suggested for areas that feature well-drained soil. The water table also needs to be low enough in order to allow discharge. Certain pretreatments like sand filters or sediment traps might be necessary to achieve infiltration and to prevent sediment or any other solids from blocking up the system.