Infiltration basins are relatively large, open depressions produced by either natural site topography or excavation. When runoff enters an infiltration basin, the water percolates through the bottom or the sides and the sediment is trapped in the basin. The soil where an infiltration basin is built must be permeable enough to provide adequate infiltration. Some pollutants other than sediment are also removed in infiltration basins. Constructed wetlands are areas inundated by water for a sufficient time to support vegetation adaped for life in saturated soil conditions.
Wetlands effectively filter sediment, nutrients, and some heavy metals from runoff waters.
Typical pollutants found in runoff from roads and highways.