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Table 2--Common sources of pollution summarized from National Water Quality Inventory Reports

Source of impairment	Description of source
Point sources
Industrial	Pulp and paper mills, chemical manufacturers, steel plants, textile manufacturers, food processing plants.
Municipal	Publicly owned sewage treatment plants that may receive indirect discharges from industrial facilities or businesses.
Combined sewers	Single facilities that treat both stormwater and sanitary sewage, which may become overloaded during storm events and discharge untreated wastes into surface waters.
Storm sewers/urban runoffa	Runoff from impervious surfaces including streets, buildings, lawns, and other paved areas that enters a sewer, pipe, or ditch before discharge into surface waters.
Land disposala	Leachate or discharge from septic tanks, landfills and hazardous waste sites.
Nonpoint sources
Agriculture	Crop production, pastures, rangeland, feedlots, other animal holding areas.
Silviculture	Forest management, tree harvesting, logging road construction.
Construction	Land development, road construction.
Resource extraction	Mining, petroleum-drilling, runoff from mine tailing sites.
Natural	Non man-induced impacts, such as floods, hurricanes, leachate from naturally occurring metals, and wildlife.

^a Storm sewers/urban runoff and land disposal include both point and nonpoint sources.

Source: U.S. Environmental Protection Agency 1998a

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