Vegetative Filtering Systems Dry Swales
Broad, mildly sloped vegetative filtering
Checkdams (may be necessary)
30” soil bed with underdrain system
Temporarily stores water quality volume
Drains between storm events within one day
Notes:
The dry swale consists of an open channel capable of temporarily storing the water quality treatment volume (WQv) and a filtering medium consisting of a soil bed with an underdrain system. The dry swale uses a volume based sizing criteria. The dry swale is designed to drain down between storm events in less than one day. The water quality treatment mechanisms are similar to bioretention practices except that the pollutant uptake is likely to be somewhat more limited since only a grass cover crop is available for nutrient uptake. In the event that surface soils clog, the dry swale has a pea gravel window on the downstream side of each checkdam to route water to the underdrain.