The Federal Water Pollution Control Act (1972), referred to as the Clean Water Act (CWA) when amended in 1977, is the principal federal law protecting surface waters in the United States. The CWA establishes the regulatory authority which is administered by the Environmental Protection Agency (EPA) and/or U. S. Army Corps of Engineers (Army Corps), directly or in concert with the states and tribes, to manage and control the discharge of pollutants into U.S. surface waters. The principal enforcement mechanisms of the law are pollutant discharge limits and permitting programs. Toward that end, the legislation authorizes EPA to establish and enforce pollution control performance standards; assist states and tribes with establishing and enforcing water quality criteria and pollution control programs; provide financial and technical assistance to states and municipalities for constructing waste water treatment facilities; and oversee other federal agencies implementing various sections of the Act or conducting activities controlled under the Act. In 1972 the CWA Section 404 established control of discharges into U.S. waters associated with dredging and filling activities. This provision has since been used to control and mitigate the loss of wetlands. The regulatory program developed to implement Section 404 of the CWA is administered by the Army Corps with oversight by EPA.
Beginning in 1987, Congress amended the Clean Water Act to broaden the definition of point sources to include stormwater discharges from industrial activities. The first phase of the program (Phase I) required certain industrial dischargers, medium and large municipal separate storm sewer systems (MS4s), and operators of construction sites greater than five acres to obtain National Pollutant Discharge Elimination System (NPDES) permits. The second phase of the program (Phase II) directed EPA to designate certain categories of dischargers for regulation under the NPDES program. Phase II requirements address urbanized areas usually with a population over 50,000 and construction projects of one acre or more. The program is designated to the States in 45 cases, usually in their State water quality agencies.
Implementation of the wetlands regulations (Section 404) and the NDPES (Section 402), along with Water Quality Certification (Section 401) programs have had the greatest impact on the transportation industry, and they will continue to have significant impacts in the future as the programs mature.
Emphasis of CWA programs over the last two decades also is shifting from a program-by-program, source-by-source, pollutant-by-pollutant, approach to more regional or watershed-based strategies. Transportation agencies increasingly are adopting watershed approaches to prevent and mitigate impacts to wetlands and other aquatic resources.
Under the watershed approach equal emphasis is placed on protecting healthy waters and restoring impaired ones. A full array of issues are addressed, not just those subject to CWA regulatory authority. The identification and adoption of watershed-based pollutant loading objectives and limits called Total Maximum Daily Loads (TMDLs) are the central elements of this approach. (More information about TMDLs is provided below.) Involvement of stakeholder groups in the development and implementation of watershed-based strategies for achieving and maintaining state water quality and other environmental goals is essential.