What are Grassed Bio-Infiltration Swales?
Grassed infiltration swales (“swales”) are depressions (collection areas) in which stormwater from roofs, streets and driveways is collected following a rain or snow event. Swales are usually found in the front portion of new lots next to the street and sidewalk. Swales are used to collect and dispose of stormwater runoff, and to remove pollutants from stormwater before it reaches underground sources of drinking water. Within a swale there is typically an elevated grate (4″ to 6″ above grade) that is the cover for a drywell. The drywell receives overflow from the swale in the event of excessive runoff. Stormwater enters swales through cuts in the curb or through catch basins and infiltrates through the grass and soil. Pollutants in the stormwater are removed by the grass and soil in this infiltration process, helping to protect the Aquifer from contamination. Drainage swales rely on the infiltration process, which is when water “soaks” into the ground and eventually recharges groundwat
