Urban stormwater runoff is a main cause of pollution for estuaries,
lakes, and rivers (U.S. EPA, 1998). In urban areas, the high proportion of
impervious surfaces such as roads, parking lots, and rooftops allows little
infiltration of stormwater, and the resulting runoff is collected in retention
ponds or directly runs into surface waters. Stormwater runoff picks
up a variety of contaminants on its way to receiving waters. Road runoff
contains metals such as copper, cadmium, zinc, organic pollutants such as
polycyclic aromatic hydrocarbons (PAH), pesticides, and microbes
(U.S. EPA, 1998).