The population of the United States is concentrated in urban areas; 82% reside in over 500 urban areas. Despite many benefits, high urbanization leads to various environmental issues, such as polluted urban road runoff, the surface stormwater created by urbanization. Urban runoff largely from impervious surfaces such as roadways and parking lots is recognized among major nonpoint pollution sources for surface water, groundwater, and soil. The transportation-associated sources of runoff pollution are principally vehicles and atmospheric deposition. Among the various stormwater pollutants, heavy metals, especially lead, copper, and zinc, are of particular concern due to their non-biodegradability, accumulation in environment, and toxicity. Nutrients in urban runoff, including phosphorous and nitrogen, are also problematic because of their ability to cause eutrophication in receiving water bodies, and contamination of groundwater.