Nonpoint Source Water Pollution 245Table 11-5. Sources of Contaminants in Urban Storm water Runoff a
Contaminant Typical sources
Sedimentlfloatables
Pesticidedherbicides
Organic materials
Metals
OiVgreasehy drocarbons
Microbial pathogens
Nutrients (N and P)
Streets, lawns, driveways, roads, construction activities,
atmospheric deposition, drainage channel erosion
Residential lawns and gardens, roadsides, utility right-of-
ways, commercial and industrial landscaped areas, soil
wash-off
Residential lawns and gardens, commercial landscaping,
animal wastes
Automobiles, bridges, atmospheric deposition, industrial
areas, soil erosion, corroding metal surfaces, combustion
processes
Roads, driveways, parking lots, vehicle maintenance
areas, gas stations, illicit dumping to storm drains
Lawns, roads, leaky sanitary sewer lines, sanitary sewer
cross-connections, animal waste, septic systems
Lawn fertilizer, atmospheric deposition, automobile
exhaust, soil erosion, animal waste, detergents=From ‘‘Preliminary Data Summary of Urban Storm Water Best Management Practices,” EPA-821-R-
99-012, USEPA, Washington, Dc, August 1999.
regulatory efforts, by enforcement of existing construction regulations, and through
public education. Street litter, for example, may be reduced by passage and enforce-
ment of anti-littering regulation, public education about the polluting effects of litter,
installation of litter collection devices, or street sweeping or vacuuming. Transporta-
tion residues like oil, gas, and grease from cars, and particulates from deteriorating
road surfaces can be reduced by selecting road surfaces less susceptible to deteriora-
tion, instituting automobile exhaust inspection programs, educating the public about
the pollution control benefits of keeping automobiles tuned up and operating properly,
or using clean-up technologies such as oil and grease separators and sedimentation
basins.
There are three major steps that can be taken to mitigate urban nonpoint source
pollution: first, reduce sur$ace runoff from urban sites; second, use source control
to reduce the amount of pollution picked up by runoff, and finally, use appropriate
technology (best management practices or BMPs) to remove or treat pollutants in the
runoff. Urban areas have a higher percentage of impervious surfaces such as roads,
sidewalks, driveways, and parking lots, and often have more disturbed soil compared
to nonurban watersheds. Because of this, a greater percentage of precipitation falling
in urban areas becomes surface runoff. Pollution control techniques that reduce the
amount of surface runoff or increase infiltration rates (e.g., infiltration trenches, rain
barrels, dry wells, porous driveways, vegetative covers) can be effective at reducing
erosion and pollution transport.