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Causess of Water Pollution - Urban Area Sources

Causes and Control of Water Pollution
Urban Areas

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Urbanization has been linked to the degradation of urban waterways. The major pollutants found in runoff from urban areas include sediment, nutrients, oxygen-demanding substances, road salts, heavy metals, petroleum hydrocarbons, pathogenic bacteria, and viruses. Suspended sediments constitute the largest mass of pollutant loadings to receiving waters from urban areas. Construction is a major source of sediment erosion. Nutrient and bacterial sources of contamination include fertilizer usage, pet wastes, leaves, grass clippings, and faulty septic tanks. Petroleum hydrocarbons result mostly from automobile sources.


NEW DEVELOPMENT -- The new development management measure is intended to mitigate the effects of new development on water quality. This measure specifies that runoff from new development be managed so as to meet two conditions:
  1. The average annual total suspended solid (TSS) loadings after construction is completed are reduced:
    a) by 80 percent, or
    b) so that they are no greater than predevelopment loadings; and
  2. To the extent practicable, post-development peak runoff rate and average volume are maintained at levels that are similar to predevelopment levels.

New developments required to obtain NPDES permits are not subject to this management measure.

WATERSHED PROTECTION/SITE DEVELOPMENT -- The purpose of these measures is to encourage comprehensive planning for development on a watershed scale and for small-scle site development as well, including planning and designing to protect sensitive ecological areas, minimize land disturbances and retain natural drainage and vegetation whenever possible.

CONSTRUCTION EROSION/SEDIMENT CONTROL -- The purpose of this measure is to reduce erosion and transport of sediment from construction sites to surface water. A sediment and erosion control plan should be developed and approved prior to land disturbance. This measure applies to construction sites of less than 5 acres.

CONSTRUCTION SITE CHEMICAL CONTROL -- This measure addresses the transport of toxic chemicals to surface water by limiting the application, generation, and migration of chemical contaminants (i.e., petrochemicals, pesticides, nutrients) and providing proper storage and disposal.

EXISTING DEVELOPMENT -- This measure addresses reduction of pollution loadings from already developed areas. Watershed management programs should be developed that identify the sources, specify appropriate controls such as retrofitting or the establishment of buffer strips, and provide a schedule by which these controls are to be implemented.

NEW ONSITE DISPOSAL SYSTEMS -- This measure addresses nutrient/pathogen loadings to surface water from new on-site disposal systems. The measure specifies that new onsite disposal systems (OSDS) are to be designed, installed and operated properly and to be situated away from open waterbodies and sensitive resources such as wetlands, and floodplains. Protective separation between the OSDS and the groundwater table is to be established. The OSDS unit should be designed to reduce nitrogen loadings in areas where surface waters may be adversely affected.

OPERATING ONSITE DISPOSAL SYSTEMS -- This management measure calls for policies and systems to operate and maintain OSDS so as to prevent surface water discharge and reduce pollutant loadings to ground water. It also calls for inspection at regular time intervals and repair or replacement of faulty systems.

POLLUTION PREVENTION -- This measure includes techniques and activities to prevent nonpoint source pollutants from entering surface waters. Primary emphasis is placed on public education to promote methods for proper disposal and/or recycling of hazardous chemicals, pet waste management strategies, management practices for lawns and gardens, OSDSs, and commercial enterprises such as service stations and parking lots.

SITING ROADS, HIGHWAYS, AND BRIDGES -- The measure calls for roads, highways, and bridges to be situated away from areas that are sensitive ecosystems and susceptible to erosion and sediment loss. The siting of such structures should not adversely impact water quality, minimize land disturbances, and retain natural vegetation and drainage features.

CONSTRUCTION PROJECTS FOR ROADS, HIGHWAYS, AND BRIDGES -- This measure calls for the development and implementation of an approved erosion and sediment control plan prior to construction, which would reduce erosion and improve retention of sediments onsite during and after construction.

CONSTRUCTION SITE CHEMICAL CONTROL FOR ROADS, HIGHWAYS, AND BRIDGES -- The measure limits toxic and nutrient loadings at construction sites by ensuring the proper use, storage, and disposal of toxic materials to prevent significant chemical and nutrient runoff to surface water.

OPERATION AND MAINTENANCE FOR ROADS, HIGHWAYS, AND BRIDGES -- This measure provides an operation and maintenance approach designed to reduce pollutant loadings to receiving waters during operation and maintenance of roads, highways, and bridges.

RUNOFF SYSTEMS FOR ROADS, HIGHWAYS, AND BRIDGES -- This measure specifies development of runoff management systems to reduce pollutant concentrations in runoff from existing roads, highways, and bridges. Runoff management systems should identify priority pollutant reduction opportunities and schedule implementation of retrofit projects to protect impacted areas and threatened surface waters.