Department of Environmental Conservation

D E C banner

Sanitary Sewer Overflow (SSO)

Sanitary Sewer Overflows (SSOs) are discharges of raw sewage from sanitary sewers and are prohibited. SSOs can release untreated sewage into basements or out of manholes and onto city streets, playgrounds or into streams, depending on where the problem in the system occurs. SSOs are often caused by:

  • Infiltration and Inflow (I/I)
    • Stormwater is collected in separate pipes and is not supposed to be connected to the sanitary sewer
  • Undersized Sewer Systems
  • Pipe/Equipment Failures
  • Unauthorized Sewer Connections
  • Deteriorating Sewer Systems
  • Fat, Oil, and Grease Blockages
  • Blockages caused by Baby Wipes, Trash, Tree Roots, etc

A few types of SSOs are unavoidable and may occur due to the following causes:

  • Vandalism
  • Extreme rainstorms
  • Acts of nature such as earthquakes or floods

SSOs contain raw sewage and can expose people to bacteria that may cause illness through contaminated water sources or recreation in waterbodies. Shellfish that are harvested for human consumption can also be contaminated with raw sewage.

Identifying Problems

The Sewage Pollution Right to Know (SPRTK) law requires municipalities to notify DEC, the Department of Health and the public about untreated or partially treated sewage discharges. This tracking of where SSO's are occurring highlights where wastewater infrastructure upgrades may be needed.

A puddle of sewage water
Sanitary sewer overflows (SSOs) may be caused
by blockages, equipment problems, inflow from
stormwater, or inflitration of groundwater.

Reducing SSO's

If an SSO occurs at a State Pollutant Discharge Elimination System (SPDES) permitted wastewater treatment facility they must evaluate the cause and implement corrective actions to prevent the SSO from happening again.

SSO's can be reduced or eliminated by:

  • Routine sewer system cleaning and maintenance
  • Reducing I/I by repairing broken or leaking sewer lines
  • Enlarging or upgrading sewer lines, pump stations, or sewage treatment plant capacity

Municipalities are required to have Operation and Maintenance plans for their sewer systems. Local sewer use laws restrict what can enter the sewer system. Publicly Owned Treatment Works (POTW) are also required to annually certify that they are not exceeding their capacity to treat the sewage properly. Many municipalities also have programs in place to ensure that the sewer systems are not overwhelmed by things other than sewage and allowable industrial waste water.

Monitoring Progress

Many communities are under Orders on Consent with compliance schedules to reduce and eliminate SSO discharges. The Orders on Consent often require an annual report describing what the municipality has done in the past year to reduce SSOs.


  • PDF Help
  • For help with PDFs on this page, please call 518-402-8111.
  • Contact for this Page
  • Division of Water
    625 Broadway
    Albany, NY 12233-3500
    518-402-8111
    Send us an email
  • This Page Covers
  • Page applies to all NYS regions