Effluent limitations for industrial facilities that discharge pollution directly to surface waters are one of the cornerstones of the national clean water program established by the 1972 Amendments to the Federal Water Pollution Control Act (FWPCA).¹ They embody Congress' decision to scrap an ineffective regulatory system based on water quality in favor of a more workable, technology-based system of effluent regulation. The pre-1972 FWPCA tied the pollution control requirements imposed on individual plants to their impact on the quality of the waterways into which they drained their wastewater.² The system did not work.³ The 1972 Amendments authorized the Environmental Protection Agency (EPA) to set nationally uniform standards, based on the pollution control technologies available, specifying the amounts of pollution that may legally be discharged by any "point source"⁴ in each industry category. In conjunction with effluent limitations for municipal sewage treatment works,⁵ federal grants to help finance the construction of such facilities,⁶ and water quality management plans for nonpoint sources of water pollution,⁷ the other cornerstones of the Act, the industrial effluent limitations are designed to achieve the FWPCA's goals of making all surface waters in the United States "fishable and swimmable" by 1983 and eliminating all pollutant discharges by 1985.⁸

The heart of the complicated system of effluent limitations for industrial sources established by the FWPCA is the technology-based standards for existing sources prescribed by §§301 and 304. Existing sources, those under construction before proposal of a new source performance standard for their industry category, are covered by effluent limitations mandated by §301 and defined by §304.⁹ New sources must comply with performance standards under §306 that are closely linked to the existing source standards.¹⁰ "New" and "existing" facilities that avoid point source regulation by discharging to publicly owned treatment works are indirectly regulated because the treatment works themselves are point sources subject to §301 effluent limitations parallel to those for industrial facilities. Such facilities must also meet §307 pretreatment standards designed to protect the treatment works should their discharges threaten its proper operation, a program that has been controversial and only partially implemented.¹¹ The Act also authorizes EPA to set effluent standards for toxic pollutants based on their harmful potential rather than the availability of treatment technology, but the agency has made no use of that authority.¹² Finally, where the otherwise applicable limitations will not clean up a body of water sufficiently to attain state water quality standards, the Act requires that stricter "water quality related effluent limitations" be imposed.¹³