Bioswales are defined as open, vegetated drainage channels that are designed to detain, treat and/or infiltrate stormwater. Bioswales most effective in contamination removal are fully vegetated and trapezoidal in shape with wide, flat bottom widths and slopes that do not exceed 6%. They consist of filter fabric, an infiltration trench, 18” substrate of rock, perforated drainage tile, compost and native vegetation. Runoff is captured, stored and slowly released back into the underlying water table. They are useful in storing, infiltrating and cleansing larger amounts of stormwater runoff from impervious surfaces such as parking lots and roads.