Retention Pond Structure

Pollution Removal

• Often called a wet pond, the retention pond continuously has water in it. The water helps break up and remove pollutants. Aquatic life will usually develop and grow in a retention pond, which helps to further break down pollution particles in the water and provide oxygen. The plants work as a natural filtration system. A retention pond's water will also play host to microorganisms which also help cleanse the water. A well-constructed retention pond will successfully remove 30 to 80 percent of all pollutants before the water is diverted to a spring or waterway, according to the University of South Alabama.

Location

• Retention ponds are usually constructed in low-lying sites to catch water runoff. The pond works well when placed in the heart of an urban area where excessive concrete streets, parking lots and structures do not allow the rainwater to seep into the soil. In such locations, the water will flow into a retention pond. The retention pond becomes a catch-all for trash and other debris that often collects in the pond.

Filtration

• The construction of retention ponds in areas with heavy agriculture is becoming exceedingly popular. A retention pond's ability to remove pollutants helps prevent the runoff of agriculture pesticides and fertilizers into the water or soil. The pond can filter out bacteria, sediments, metals and solids. It will also remove petroleum pollutants from roadways. Adequate filtration takes time; phosphorus can take up to 100 days to leave the water, according to the Scottish Environment Protection Agency.

Construction

• Retention ponds usually cover 1 acre of land. A ledge that measures approximately 10 feet usually circles around the perimeter of the pond. The slope helps someone who's fallen into the pond, as the ledge gradually slopes before plunging into deeper water. The middle of the retention pond usually measures 8 to 10 feet in depth. Never swim or wade into a retention pond. The water within a pond can pose a danger because geese and ducks flock to the water. Their fecal matter can cause a buildup of E coli.