Hydrophilic plants are specially suited to survive in soils that are always wet. Cat tails and Phragmites are competing species of hydrophilic plants. The narrow-leaved variety is more tolerant of pollution. The cattails here are narrow-leaved. Often wetlands that are polluted have the Common Reed known as Phragmites instead of catails.
Wetlands act as a giant filter sorbing the pollution in the water that flows through it.
In this setting solid pollutants sink to the bottom of the marsh increasing the clarity of the water. With time more sediments accumulate burying the pollutants. Bacteria in the bottom sediments break down the pollutants to less harmful materials. The storm water system is finally connected to these large recharge basins which have been placed in an abandoned stream valley which has been dammed by the Long Island Railroad track. State highway 25A follows this valley to the west.