As we continue to discuss stormwater features, we wouldn’t be doing the topic justice if we didn’t talk about ponds. It seems like stormwater ponds are everywhere, but as we will learn, no 2 ponds are created alike. There are many different types of ponds and telling them apart can be tricky.
As we’ve already learned, stormwater control means several things – controlling the water quality of the stormwater runoff as well as controlling the rate which stormwater is leaving the site. Ponds can do all of these things. They can also be created to treat for one specific pollutant, as in the case of industrial treatment ponds. They can even be created for temporary use during construction.
Some ponds are designed solely for water quality. These ponds often operate by maintaining a certain depth and/or a certain surface area, allowing sediments and other pollutants to settle out of the stormwater before it flows on to another stormwater feature downstream. They go by names such as wetponds, sediment cells, treatment ponds, etc. Often, if a pond is perennially full of water, you can make an educated guess that it is a treatment pond. However, that is not always true.
Some ponds are designed to impound water for a short time before the water is discharged downstream. These are called detention ponds. In order to keep the water from releasing too quickly, there is often a restrictor that keeps the water from flowing out too fast. This serves to keep the downstream river banks from erosion due to receiving more flow than they have experienced in the past. This type of pond will be full for a time during and shortly after a storm, but will soon drain down again and be nearly empty (often there is a residual water surface remaining).
Other ponds serve to infiltrate water into the ground. They are called infiltration ponds. These ponds often don’t look like ponds at all because they contain no water except right after a storm.
Telling the type of pond just by visual clues can be tricky. If it has standing water in it, it might be a treatment pond or it could be a detention pond. If you see a pond area, but with no water in it, it is likely an infiltration pond. The only real way to tell about the types of ponds on a site is to have a professional review the design of the stormwater system, including the plans and the Stormwater Manual.
– See more at: http://www.catchallenvironmental.com/blog/ponds-ponds-and-more-ponds#sthash.axgKqVrE.dpuf