Wet facilities
These facilities typically contain year-round water and often have significant aquatic vegetation. Water levels may rise during a storm, but should not breach the structure.
Wetpond (above) is an open basin with a permanent pool of water. Sediment and pollutants settle to the bottom. Often combined with a detention pond.
Treatment wetland (below) is a shallow pond that uses dense wetland vegetation and settling to filter sediment and oily materials. It often provides wildlife habitat.