A drywell is an excavated pit or structural chamber filled with gravel or stone that provides temporary storage of stormwater runoff from rooftops.
The storage area may be constructed as a shallow trench or a deep well. Rooftop runoff is directed to these storage areas and infiltrates into the surrounding soils prior to the next storm. The pollutant removal capability of drywells is directly proportional to the amount of runoff that is stored and allowed to infiltrate.
