Addressing Combined Sewer Overflows Using Green Infrastructure

Many communities with combined sewer systems are installing green infrastructure in addition to gray infrastructure projects to more effectively meet their Clean Water Act (CWA) requirements. Green infrastructure can reduce the volume and occurrence of Combined Sewer Overflows (CSOs) and reduce pollutants in stormwater, often while providing cost savings and creating more livable communities. EPA supports integrating green infrastructure approaches into long-term control plans (pdf) and into remedies for noncompliance with the CSO Control Policy. The design flexibility and multiple benefits green infrastructure provides make it a strong candidate to complement existing gray infrastructure projects. Communities may also use an integrated planning approach to address their CSOs.

Under the CWA, permittees with combined sewer systems are required to reduce the volume and frequency of their overflows during storm events. Green infrastructure can reduce the volume of water going into combined sewer systems during precipitation events, which may reduce the frequency and volume of overflows. Green infrastructure can also slow the delivery of stormwater to sewer systems, helping to mitigate peak flows in the collection systems and potentially at the treatment plant. Additionally, green infrastructure can provide filtration through soil or engineered media, which can reduce pollutant loadings entering the collection system.

Select one of the community spotlights below, which showcase three communities that have implemented green infrastructure in resourceful and inventive ways to comply with the CSO Control Policy. Check out the Using Green Infrastructure to Address CWA Enforcement table for additional community examples.

• Washington, D.C.

  

  Getting Realistic by Using Gray and Green Infrastructure in D.C.

  DC Water

• Atlanta, Georgia

  

  Energizing Green Infrastructure Through City Programming

  City of Atlanta Department of Watershed Management

• Louisville, Kentucky

  

  Leading with Green Infrastructure in Louisville

  Louisville Metropolitan Sewer District

Resources

• Greening CSO Plans: Planning and Modeling Green Infrastructure for Combined Sewer Overflow (CSO) Control (pdf)
• Combined Sewer Overflow (SCO) Model for Small Communities
• Green Infrastructure Permitting and Enforcement Series Fact Sheet 2: Combined Sewer Overflows (pdf)
  • See page 5 checklist: A General Methodology for Establishing a Quantitative Green Infrastructure Implementation Target (pdf)
• Green Infrastructure Permitting and Enforcement Series Supplement 1: Consent Decrees that Include Green Infrastructure Provisions (pdf)
• Green Infrastructure Permitting and Enforcement Series Supplement 2: Consent Decree Language Addressing Green for Gray Substitutions (pdf)
• Green Infrastructure Modeling Toolkit
• EPA's Green Infrastructure in Parks 2017: A Guide to Collaboration, Funding, and Community Engagement (pdf)
• Visit the EPA Resources page to learn about the variety of EPA tools that can be used to support planning and design decisions for green infrastructure implementation.