bioswales require a certain soil composition that does not contain more than 5% clay. the soil itself before implementation should not be contaminated. bioswales should be constructed with a longitudinal slope to allow sediments to settle. maximum slope of bioswales is 3:1. a minimum clearance is required to ensure that other infrastructure would not be damaged. the overfill drain should be located at least 6 inches above the ground plain to allow for maximum concentration time of stormwater runoff in the bioswales. rocks can also be used to slow down the runoff velocity. the use of filters is important to prevent inlets from becoming blocked by sediments or trash.