What is a stormwater attenuation lagoon?
Stormwater attenuation lagoons are used to control the flow of stormwater runoff. Also known as detention basins, retention ponds, retarding ponds, dry ponds or holding ponds, these lagoons are man-made.
Detention basins are surface storage basins or facilities that provide flow control through attenuation of stormwater runoff. They also facilitate some settling of particulate pollutants.
Detention basins are normally dry and in certain situations, the land may also function as a recreational facility. However, basins can also be mixed, including both a permanently wet area for wildlife or treatment of the runoff and an area that is usually dry to cater for flood attenuation.
Basins tend to be found towards the end of the SuDS management train, so are used if extended treatment of the runoff is required or if they are required for wildlife or landscape reasons.
How does a detention basin work?
A detention basin (stormwater attenuation lagoon) prevents flooding by controlling the amount of stormwater that is released into the environment at any given time. When a storm event occurs, the detention pond simply fills up and stores large volumes of rainwater temporarily. It will then gradually release this water, thereby reducing flooding and erosion downstream.
What is the difference between a detention and retention basin?
In contrast to dry detention ponds, retention ponds will hold a permanent pool of water and can also be referred to as wet ponds. A retention pond is usually created because of a high groundwater table (the groundwater is near the surface of the earth).
How are stormwater attenuation lagoons created?
These basins are typically created during the construction of new building development projects, such as housing estates or shopping centres. They are a best practice method of preventing general flooding and controlling extreme floods, such as a 1 in a 100-year storm event. The basins help control excess urban runoff, which is created as a result of man-made impervious surfaces such as rooftops, roads etc.
The lagoons are created by excavating an area of land and lining it with a permeable geomembrane. There will generally be a small opening at the lowest point of the structure. The size of this opening is determined by the capacity of underground and downstream culverts and washes to handle the release of the contained water.
What geomembranes do we supply?
We can supply and install geomembrane liners and waterproof lining systems for reservoirs, lakes, ponds, canals and lagoons. By understanding your requirements we can quickly identify the best lining solution for your specific project. We provide a full 360-degree service that includes detailed design, full installation and inspection.
Our high quality, CE marked range of waterproof lining products includes: Landflex PEHD (HDPE), Landflex PELL (LLDPE), Landflex BR (Butyl Rubber), Landflex EP (EPDM Rubber). Our Landflex G3000, G4000 and G6200 CBR puncture resistant liner protection geotextile are designed to complement the range, providing excellent protection against damage to our liners.
Do we install stormwater lagoons?
We can supply the geomembrane only or provide you with a complete package. This includes supply, design and also install your lagoon for you. Our installation team has over 25 years of experience in rural construction and are ISO:9001, ISO:14001, Achilles and ConstructionLine accredited.
To find out more, contact our specialist at Cotterill Civils for expert advice on stormwater lagoons on 0121 351 3230.