Environmental Engineering FOURTH EDITION

246 ENVIRONMENTALENGINEERING

In addition to reducing surface runoff, we can emphasize source control to reduce
the amount of pollutants deposited on impervious surfaces. Source control can be
attained by increasing public education, providing waste disposal sites (e.g., pet waste
disposal stations, hazardous waste disposal sites), introducing appropriate planning
and regulatory policies, and enforcing pollution control regulations. Street sweeping,
the oldest and least expensive source control technique, is still used in most cities. Street
sweeping reduces sediment loading in runoff but fails to pick up the finer particles that
are often the most significant source of pollution (fine silts and clays carry a dispro-
portionately large amount of biodegradable and toxic substances, metals, and nutrients
compared to coarser sediments). Street vacuuming is more efficient in collecting the
small particles, but is more expensive and often ineffective during wet periods. Street
flushing is an effective way to clean street surfaces, but only if the runoff is retained in
catch basins, and the basins are cleaned periodically to remove refuse and other solids.
The final step in mitigating urban nonpoint source pollution is to use appropriate
structural and nonstructural BMPs to reduce the concentration of pollutants in storm
runoff (Table 11-6).

Table 11-6. Structural and Nonstructural Storm Water BMPs‘

Structural BMPs

Infiltration systems

Detention systems
Retention systems
Constructed wetlands
Filtration systems
Vegetated systems

Examples

Infiltration basins, porous pavement, infiltration trenches,

infiltration wells

Detention basins, underground vaults, pipes, and tanks

Wet ponds, retention tanks, tunnels, vaults, and pipes

Artificial wetlands, wetland basins, wetland channels

Sand filters, misc. media filters

Grass filter strips, vegetated swales

Nonstructural BMPs

Automotive product and household hazardous material disposal
Commercial and retail space good housekeeping
Industrial good housekeeping
Modified use of fertilizers, pesticides, and herbicides
Lawn debris management
Animal waste disposal
Maintenance practices (e.g., catch basin cleaning)
Illicit discharge detection and elimination
Education and outreach programs
Storm drain inlet stenciling
Minimizing directly connected impervious surfaces
Low-impact development and land use planning

‘From “Preliminary Data Summary of Urban Storm Water Best Management Practices,” EPA-821-R-

99-012, USEPA, Washington, DC, August 1999.