Clean Water Act (1972) – This law serves as the backbone of many other water protection rules that came after its enactment and provides two key regulatory sections to meet water quality standards. On overview and links to more Information on TMDLs and NPDES regulations is provided. 

Section 303 requires States to establish Water Quality Standards for navigable waters that meet federal expectations of quality. This section also requires states to periodically develop lists of “impaired waters” – those that do not meet water quality standards – and establish total maximum daily loads (TMDLs) of pollutants that each water body can carry while still supporting aquatic life and/or remain swimmable and fishable.

[More information available at: http://water.epa.gov/scitech/swguidance/standards/history.cfm]

Section 402 of the Clean Water Act makes it illegal to discharge any point source pollution into “waters of the United States” without a permit from the U.S. Environmental Protection Agency (EPA). This section established the National Pollutant Discharge and Elimination System (NPDES) of permits and required EPA to set limits to and enforce the amount of pollution that can be discharged into waterways from any given point source. Although EPA is the overall administrator of the NPDES program, in most cases the States serve as the permitting and enforcement entity.

[More information available at: http://cfpub.epa.gov/npdes/cwa.cfm?program_id=6]

1987 Amendments to Clean Water Act – The law was amended to include “stormwater discharges from an industrial activity” in the list of sources that must be covered by an NPDES permit. This definition includes stormwater discharges from municipal storm sewer systems, or “MS4s”, typical of impervious urbanized areas. NPDES rules affecting MS4 localities were rolled out in two phases:

• Phase I (1990): Each medium and large city (and certain counties) with a population of 100,000 or more must obtain an NPDES permit for discharges of stormwater from conveyance systems within its boundaries.
  

• Phase II (1999): Smaller MS4s within a census-defined “urbanized area” must also obtain an NPDES permit for its stormwater discharges.
  

• In both instances, the permitted entity must create an ongoing stormwater management program to reduce stormwater pollution and illicit discharges.

[More information available at: http://cfpub.epa.gov/npdes/stormwater/munic.cfm]