Point and Nonpoint Sources of Pollution
November 20, 2008(Excerpted from EPA and RIDEM web sites)
Water pollution degrades surface waters making them unsafe for drinking, fishing, swimming, and other activities. Pollution sources are divided into two categories – point and nonpoint sources.
Point sources are pollutants introduced to the environment through discrete conveyances such as pipes or man-made ditches. As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources. Under the NPDES program, all municipal, industrial and commercial facilities that discharge wastewater directly from a point source (a discrete conveyance such as a pipe, ditch or channel) into a receiving waterbody (lake, river, ocean) are issued an NPDES permit. Facilities that discharge wastewater to a publicly owned treatment works (POTW), which in turn discharges into the receiving waterbody, are not subject to NPDES permits; rather they are controlled by the national pretreatment program.
The state or federal agencies that issue permits determine the volume of effluent that can be discharged from a given facility and set limits in the permit to ensure that water quality is not compromised. The permits expire after five years. NPDES permits are divided into two categories: municipal and industrial. Each category is then subdivided into major (large dischargers) and minor (small dischargers). Some of the permits cover single facilities while others, called general permits, cover all of the facilities of a certain type in a given state.
In Rhode Island, the NPDES program is managed by the RIDEM (http://www.dem.ri.gov/programs/benviron/water/permits/ripdes/index.htm).
In Massachusetts, the NPDES program is handled by EPA Region 1 (http://www.epa.gov/ne/npdes/mass.html).
Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. These pollutants include:
- Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas;
- Oil, grease, and toxic chemicals from urban runoff and energy production;
- Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks;
- Salt from irrigation practices and acid drainage from abandoned mines;
- Bacteria and nutrients from livestock, pet wastes, and faulty septic systems.
To help control nonpoint sources, Section 319 of the Clean Water Act, enables the development of state management programs and establishes grant allotments.
Rhode Island’s nonpoint source management program is part of RIDEM (http://www.dem.ri.gov/programs/benviron/water/quality/nonpoint/index.htm) and concentrates on the development of innovative pollution management policies and water quality management using the watershed approach while focusing on areas such as septic programs and wetlands policy, marina management, land use planning, soil erosion and sediment control, and stormwater management.
Massachusetts’ nonpoint source management program in managed by the MA Department of Environmental Protection. (http://www.mass.gov/dep/water/resources/nonpoint.htm) .