page_title: Clean Water Act
section_title: Nonpoint sources
hierarchical_section_title: Clean Water Act / Pollution control strategy / Nonpoint sources
caption_attribution_description: English: "National Map of Regulated MS4s", showing the location of Municipal Separate Storm Sewer Systems (MS4) in the United States. The MS4s are regulated by discharge permits under the National Pollutant Discharge Elimination System (NPDES). Phase I Ms4s are medium and large cities or certain counties with populations of 100,000 or more. Phase II MS4s are smaller systems in U.S. Census Bureau defined urbanized areas, as well as MS4s designated by the permitting authority (EPA or state agency).
context_page_description: The Clean Water Act is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibilities of the states in addressing pollution and providing assistance to states to do so, including funding for publicly owned treatment works for the improvement of wastewater treatment; and maintaining the integrity of wetlands.
  The Clean Water Act was one of the United States' first and most influential modern environmental laws. Its laws and regulations are primarily administered by the U.S. Environmental Protection Agency in coordination with state governments, though some of its provisions, such as those involving filling or dredging, are administered by the U.S. Army Corps of Engineers. Its implementing regulations are codified at 40 C.F.R. Subchapters D, N, and O.
  Technically, the name of the law is the Federal Water Pollution Control Act. The first FWPCA was enacted in 1948, but took on its modern form when completely rewritten in 1972 in an act entitled the Federal Water Pollution Control Act Amendments of 1972.
context_section_description: Congress exempted some water pollution sources from the point source definition in the 1972 CWA and was unclear on the status of some other sources. Such sources were therefore considered to be nonpoint sources that were not subject to the permit program.
  Agricultural stormwater discharges and irrigation return flows were specifically exempted from permit requirements. Congress, however, provided support for research, technical and financial assistance programs at the U.S. Department of Agriculture to improve runoff management practices on farms. See Natural Resources Conservation Service.
  Stormwater runoff from industrial sources, municipal storm drains, and other sources were not specifically addressed in the 1972 law. EPA had declined to include urban runoff and industrial stormwater discharges in its initial implementation of the NPDES program, and subsequently the agency was sued by an environmental group. In 1977, the D.C. Circuit Court of Appeals ruled that stormwater discharges must be covered by the permit program.
  Research conducted starting in the late 1970s and 1980s indicated that stormwater runoff was a significant cause of water quality impairment in many parts of the US. In the early 1980s, the EPA conducted the Nationwide Urban Runoff Program (NURP) to document the extent of the urban stormwater problem. The agency began to develop regulations for stormwater permit coverage but encountered resistance from industry and municipalities, and there were additional rounds of litigation. The litigation was pending when Congress considered further amendments to the CWA in 1986.
  In the Water Quality Act of 1987, Congress responded to the stormwater problem by defining industrial stormwater dischargers and municipal separate storm sewer systems (often called "MS4") as point sources, and requiring them to obtain NPDES permits, by specific deadlines. The permit exemption for agricultural discharges continued, but Congress created several programs and grants, including a demonstration grant program at the EPA to expand the research and development of non point controls and management practices.
caption: Map of municipal separate storm sewer systems
exif: {}