Combined Sewer Overflow Additional Resources

In support of the combined sewer overflow (CSO) program, EPA developed resources on the following:

• Climate Change
• CSO Control Policy
• CSO Long-Term Control Plan
• Financial Capability
• Green Infrastructure
• Monitoring and Modeling
• Nine Minimum Controls
• Permitting CSOs
• Reports to Congress
• Smart Technology for CSO Management
• Water Quality

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Climate Change

• A Screening Assessment of the Potential Impacts of Climate Change on Combined Sewer Overflow Mitigation in the Great Lakes and New England Regions (February 2008) (pdf) (338.59 KB)
  Provides a screening-level assessment of the potential impact of future climate change on CSOs in the New England and Great Lake regions.
• Creating Resilient Water Utilities (CRWU)
  EPA's CRWU initiative provides drinking water, wastewater, and stormwater (water sector) utilities with practical tools, training, and technical assistance needed to increase resilience to climate change.

CSO Control Policy

• Implementation of the CSO Policy (May 19, 1998) (pdf) (604.54 KB)
  Discusses implementing the CSO control policy and where heightened efforts are necessary.
• Implementation of the Nine Minimum Controls (November 18, 1996) (pdf) (210.72 KB)
  Calls attention to the January 1, 1997 deadline for implementing minimum controls by NPDES permittees with combined sewer systems.
• Combined Sewer Overflows Guidance for Nine Minimum Controls (May 1995) (pdf) (3.69 MB)
  Provides information on minimum technology-based controls for communities to use to address CSO problems.

CSO Long-Term Control Plan

• Long-Term Control Plan (LTCP) Review Checklist (June 2022)
  Checklist designed to help CSO permittees and NPDES authorities determine if LTCPs meet the requirements of the CSO Control Policy and conform with EPA guidance on developing LTCPs.
• Green Long-Term Control Plan-EZ Template: A Planning Tool for Combined Sewer Overflow Control in Small Communities (April 2011)
  Planning tool for small communities considering using green infrastructure when developing an LTCP to address water pollution problems related to CSOs.
• Combined Sewer Overflows Guidance for Long-Term Control Plan (September 1995) (pdf) (13.51 MB)
  Describes how municipalities can develop comprehensive long-term control plans (LTCPs) that recognize the site-specific nature of CSOs and their impacts on receiving water bodies.

Financial Capability

• Proposed 2022 Clean Water Act Financial Capability Assessment Guidance (February 2022) (pdf) (1.48 MB)
  Outlines strategies for communities to support affordable utility rates while planning investments in water infrastructure that are essential for Clean Water Act implementation.
• Financial Capability Assessment (FCA) Framework (November 24, 2014) (pdf) (411.89 KB)
  Identifies key elements of EPA's approach to evaluating the financial capability of municipalities to inform schedules. The FCA framework provides additional information that could help communities provide a “more accurate and complete picture” of their financial capability.
• Combined Sewer Overflows Guidance for Financial Capability Assessment and Schedule Development (February 1997) (pdf) (2.32 MB)
  Explains how a community can assess its financial capability and how this assessment and other factors identified in the CSO control policy can be used to develop compliance schedules for implementing CSO controls.
• Combined Sewer Overflows: Guidance for Funding Options (August 1995) (pdf) (2.67 MB)
  Describes a broad spectrum of options for funding capital, debt service, and operational costs of CSO controls. It includes benefits and limitations of the options.

Green Infrastructure

• Greening CSO Plans: Planning and Modeling Green Infrastructure for Combined Sewer Overflow (CSO) Control (pdf) (1.95 MB)
• Green Infrastructure Permitting and Enforcement Series (June 2012) 
  Series of fact sheets on integrating green infrastructure concepts into permitting, enforcement, and water quality standards actions.
• Examples of Settled Clean Water Act Enforcement Cases that Include Green Infrastructure

Monitoring and Modeling

• Combined Sewer Overflow (CSO) Model for Small Communities (June 2022)
  Planning tool for small communities that want a simple approach to estimating a CSO occurrence, as well as treated or untreated CSO volume over a 24-hour period, and have limited resources to invest in more advanced CSO monitoring and modeling.
• Post-Construction Compliance Monitoring (PCCM) Checklist (June 2022)
  Checklist designed to help CSO permittees and NPDES authorities develop and evaluate PCCM programs to meet the requirements of the CSO Control Policy.
• CSO Post Construction Compliance Monitoring Guidance  (May 2012) (pdf) (10.05 MB)
  Presents guidance on developing a post-construction compliance monitoring program to assess the effectiveness of CSO controls.
• Combined Sewer Overflows Guidance For Monitoring and Modeling (January 1999) (pdf) (3.76 MB)
  Provides guidelines for using monitoring and modeling in the development and implementation of a CSO control program.

Nine Minimum Controls

• Combined Sewer Overflows Guidance for Nine Minimum Controls (May 1995) (pdf) (3.69 MB)
  Calls attention to the January 1, 1997 deadline for implementing minimum controls by NPDES permittees with combined sewer systems.
• Combined Sewer Overflows Guidance for Long-Term Control Plan (September 1995) (pdf) (13.51 MB)
  Provides information on minimum technology-based controls for communities to use to address CSO problems.

Permitting CSOs

• Combined Sewer Overflows Guidance For Permit Writers (September 1995) (pdf) (25.75 MB)
  Describes how to develop and issue NPDES permits with CSO conditions that reflect the CSO Control Policy. This guidance is intended primarily for NPDES permit writers.
• Combined Sewer Overflows Guidance for Screening and Ranking (August 1995) (pdf) (1.35 MB)
  Provides an informal tool to help permitting authorities establish CSO permitting priorities. It might also help permittees rank their CSOs to best allocate their resources.

Reports to Congress

• Report to Congress: Combined Sewer Overflows into the Great Lakes Basin (April 2016) (pdf) (4.1 MB)
  Assesses the implementation status of LTCPs in the Great Lakes Basin. The report also summarizes existing information on the occurrence and volume of discharges from CSOs in the Great Lakes Basin during 2014.
• Report to Congress: Combined Sewer Overflows to the Lake Michigan Basin (September 2007) (pdf) (1.81 MB)
  Assesses the occurrence of CSOs in the Lake Michigan drainage basin. The report identifies EPA actions to ensure that state permitting and enforcement efforts are consistent with the national CSO Control Policy and Clean Water Act, and lead to further reduction in CSO discharges to Lake Michigan.
• Report to Congress: Impacts and Control of Combined Sewer Overflows and Sanitary Sewer Overflows (August 2004) (pdf) (17.98 MB)
  Presents a comprehensive characterization of CSOs and sanitary sewer overflows (SSOs), including the extent to which they cause environmental and human health impacts, technologies used by municipalities to address their impacts, and resources spent by municipalities to control CSO and SSO discharges.
  • Report to Congress - Fact Sheet (August 2004) (pdf) (14.67 KB)
• Report to Congress: Implementation and Enforcement of the Combined Sewer Overflow Control Policy (December 2001) (pdf) (7.01 MB)
  Identifies progress made in implementing and enforcing CSO controls prior to, and because of, the 1994 CSO Control Policy.

Smart Technology for CSO Management

• Smart Data Infrastructure for Wet Weather Control and Decision Support (March 2021) (pdf) (8.74 MB)
  Shares how municipalities, utilities, and related organizations can use advanced monitoring data to support wet weather control and decision-making in real time or near real time.
• Emerging Technologies for Wastewater Treatment and In-Plant Wet Weather Management Fact Sheet (pdf) (7.46 MB, 2013)
  The guide provides information on emerging and innovative wastewater treatment technologies.

Water Quality

• Compliance Schedules for Water Quality-Based Effluent Limitations in NPDES Permits (May 10, 2007) (pdf) (55.77 KB)
  Provides a framework for the review of permits consistent with the Clean Water Act and its implementing regulations.
• Guidance: Coordinating Combined Sewer Overflow (CSO) Long-Term Planning with Water Quality Standards Review (July 31, 2001) (pdf) (485.75 KB)
  Addresses impediments to implementing the water quality-based provisions of the CSO Control Policy and actions states and CSO communities should take to overcome them.
• Water Quality-Based and Technology-Based CSO Requirements (July 7, 1999) (pdf) (257.48 KB)
  Clarifies that NPDES permitting authorities must determine best available technology and best conventional pollutant control technology on a case-by-case basis during the permitting process. It also suggests that permitting and water quality programs coordinate closely to reach agreement on the requirements of a LTCP.