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Nonpoint Source Pollution


Nonpoint source (NPS) pollution is pollution that originates from diffuse sources that are difficult to measure directly. Water (usually in the form of rainfall) moving over and through the ground picks up the pollutants and carries them into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. The Louisiana Department of Environmental Quality has classified nonpoint source pollution in Louisiana into nine categories:

  1. Agriculture: Agriculture includes both crop and animal production. Estimates from the 1993 Louisiana Nonpoint Source Pollution Assessment Report indicated that 30 percent of nonpoint source water quality impairments in Louisiana were associated with agricultural production.
  2. Construction: Construction activities include the development of homes, businesses, industrial areas, bridges, highways, and streets. The rate of erosion from construction sites is 10 times greater than that from agricultural land, 200 times that from pasture land, and 2,000 times more than erosion from forest land.
  3. Home Sewage Systems: Approximately 87 percent of the soils in the state are not really suitable for home sewage treatment systems. Over 1.3 million people in Louisiana utilize these types of systems. Louisiana's 1993 Nonpoint Source Pollution Assessment Report estimated that over 50 percent of these systems are malfunctioning because of incompatible soil types or lack of maintenance.
  4. Hydromodification: Hydromodification includes channelization and dredging.
  5. Resource Extraction: Resource extraction operations refer to non-coal mining activities, such as sand and gravel mining.
  6. Saltwater Intrusion and Encroachment: The introduction, accumulation, or formation of saline water in a water of lesser salinity takes two forms: saltwater intrusion refers to surface water contamination while saltwater encroachment refers to the contamination of ground water.
  7. Silviculture: Forestry-related activities include road construction and use, timber harvesting, regeneration methods, site preparation, mechanical equipment operation, prescribed burning, and application of chemicals.
  8. Urban Run-off: Precipitation in urban areas washes pollutants into storm drains. In waters of Louisiana identified by the Louisiana Water Quality Inventory Report as not fully supporting their designated uses, urban NPS pollution attributed to 9.2 percent of major impacted rivers, 7.2 percent of moderately impacted rivers, 7.5 percent of moderately impacted lakes, and 10.3 percent of moderately impacted estuaries. In all, approximately 10 percent of nonpoint source water quality impairments in Louisiana are associated with urban runoff.
  9. Coastal: The Louisiana Department of Environmental Quality gives special attention to nonpoint source pollution in coastal areas. As a result, coastal nonpoint source pollution forms the ninth category.

In the 1984 Report to Congress on NPS pollution in the U.S., the U.S. Environmental Protection Agency estimated that 90-95% of average daily loading of sediments and nitrogen and 60% of organic matter and phosphates were attributable to NPS pollution. In 1985 the Association of State and Interstate Water Pollution Control Administrators did a nationwide survey to evaluate NPS pollution. Their survey indicated that in Louisiana, 75% of rivers, 56% of lakes, and 76% of estuaries had water quality problems related to nonpoint source pollution. As a result, Congress amended the Water Pollution Control Act in 1987 to establish the Section 319 Nonpoint Source Management Program to help focus state and local nonpoint source efforts.


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Last updated Monday, November 17, 2003 7:02.