CSO REGULATIONS OVERVIEW
CSOs are point source discharges and are subject to National Pollutant Discharge Elimination System (NPDES) permit requirements, including the technology-based and water quality-based requirements of the Clean Water Act (CWA). CSOs are exempt from CWA secondary treatment standards, based on a 1980 Federal District Court ruling (Montgomery Environmental Coalition v. Costle, 646 F2d 568 (D.C. Cir. 1980)).
Nationwide, 859 NPDES permits authorize discharges from 9,471 CSO outfalls in 32 states. Most of the CSO communities are located in the Northeast and Great Lakes regions, but some are located in the Midwest, Southeast, and Pacific Northwest.
The first federal effort to regulate CSOs occurred when EPA issued a National Combined Sewer Overflow Control Strategy on August 10, 1989 (54 FR 37370). The 1989 CSO Control Strategy recommended that all CSOs be identified and categorized according to their status of compliance with NPDES requirements. The CSO Control Strategy set forth three objectives:
|||Ensure that if CSOs occur, they do so only as a result of wet weather.|
|||Bring all wet weather CSO discharge points into compliance with the technology-based and water quality-based requirements of the CWA.|
|||Minimize the impacts of CSOs on water quality, aquatic biota, and human health.|
the CSO Control Strategy charged all states to develop permitting strategies
designed to reduce, eliminate, or control CSOs.
In early 1992, EPA accelerated efforts to bring combined sewer systems with CSOs into compliance with the CWA. The efforts included negotiations with representatives of the regulated community, state regulatory agencies, and environmental groups. The initiative resulted in the development of the CSO Control Policy, which was published in the Federal Register on April 19, 1994. The key principles of the CSO Control Policy are:
|||Provide clear levels of control that would be presumed to meet appropriate health and environmental objectives.|
|||Provide sufficient flexibility to municipalities, especially financially disadvantaged communities, to consider the site-specific nature of CSOs, and to determine the most cost-effective means of reducing pollutants and meeting CWA objectives and requirements|
|||Allow a phased approach to implementation of CSO controls considering a community's financial capability.|
|||Review and revise, as appropriate, water quality standards and their implementation procedures when developing CSO control plans to reflect the site-specific wet weather impacts of CSOs.|
|||Ensure that each permit, order or decree issued after December 2000 for a discharge from a municipal CSS "conform" to the CSO Control Policy.|
|||Develop and submit a report to Congress on the progress made by EPA, states, and municipalities in implementing and enforcing the CSO Control Policy.|
|||Develop and submit a report to Congress on the extent of human health and environmental impacts from CSOs and SSOs (sanitary sewer overflows), quantify and characterize resources spent by municipalities to address these impacts, and evaluate the technologies used to control overflows. This Report should be delivered to Congress in December 2003.|
|||Complete guidance on integrating the development of LTCPs with the review of water quality standards for CSO-impacted waters. The guidance was completed in August 2001.|
The "conform" language from the December 2000 changes to the CWA effectively makes the CSO Control Policy law; EPA is in the process of defining conform. This definition is likely to have a major impact on permit requirements in some states, as state-to-state differences in CSO permitting requirements exist.