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Sanitary Sewer Overflows FAQ


The Prince William County Service Authority works diligently to operate its sanitary sewer system safely and reliably. The Service Authority’s sanitary sewer system comprises approximately 60 sewage lift stations and 1,100 miles of gravity and pressurized sewer mains that collect and transport domestic, commercial and industrial wastewater to treatment facilities. The Service Authority’s Sanitary Sewer System Preventative Maintenance Program includes video inspections of sewer mains and manholes, sewer main and manhole rehabilitation, and pump station and sewer main replacements. In addition, the Service Authority performs weekly physical inspections and maintenance of each sewage pump station. Occasionally, a sanitary sewer overflow can occur, resulting in the release of raw sewage from the system before it reaches a wastewater treatment plant. The U.S. Environmental Protection Agency (EPA) estimates that up to 75,000 SSOs occur throughout the country every year. The Service Authority has consistently been among the top-performing public sewer agencies in the country, which average two or fewer SSOs per year for each 1,000 miles of sewer mains in their systems.

Frequently Asked Questions

Click on a topic below to view the answers.

What is an SSO?

An SSO is an overflow of untreated or partially treated sewage from a sanitary sewer system.

Why do SSOs occur?

SSOs occur occasionally in almost every sewer system. Causes of SSOs include, but are not limited to:

  • Inappropriate materials placed into sewers, such as fats, oils and grease (FOG) and some household products such as baby and facial wipes, sanitary pads and tampons. All of these can create blockages.
  • Tree roots and/or excessive stormwater or groundwater entering sewer lines through defects or cracks.
  • Inappropriate connections such as sump pumps, roof gutters and downspouts, foundation drains and area drains.
  • Power loss.
  • Equipment failures and breaks.
  • Intentional acts of vandalism.
  • Heavy rainfall and natural disasters.


What should I do if I encounter an SSO?

You should avoid contact with any water or other contents released from the sanitary sewer system as a result of an SSO and immediately report it to the Service Authority’s Emergency Dispatch line at (703) 335-7982.

More information on the extent of environmental and human health impacts caused by SSOs can be found in EPA report Impacts and Control of CSOs and SSOs.

Is the Service Authority required to report SSOs to regulating and enforcing agencies?

The Virginia Department of Environmental Quality (VDEQ) requires that all SSOs greater than 1,000 gallons be reported to the Department within 24 hours of discovering the SSO has occurred. Regardless of the size of the SSO, VDEQ also requires that any SSO that reaches a body of water and/or that results in a fish kill be reported. In addition, VDEQ requires that the area of a reportable SSO be marked with signs for at least seven days that the area has experienced an SSO. Finally, VDEQ maintains a Pollution Response Program (PREP) database, which is accessible to the public. This database shows all open SSO cases throughout the state, as well as a five-year period of record for closed SSO cases.

How does the Service Authority notify the public if an SSO occurs?

The Service Authority publishes a public notification and map of the affected area on its website, if a reportable SSO occurs. The Service Authority also posts a notification and a link to the website on its Facebook and Twitter accounts.

If sewage reaches a body of water, the Service Authority places signage at the site of a reportable SSO. The signs state in English and Spanish that contact with the water impacted by the SSO may cause an increased risk of illness, and remain in place for at least seven days.

If an SSO occurs within or up to 1,000 feet upstream of a community managed by a Homeowners Association or property management company, the Service Authority notifies the those entities if contact is available.

What does the Service Authority do to reduce the potential of SSOs?

The Service Authority has invested significantly and continues to invest in sewer improvements to reduce the likelihood of SSOs by:

  • Cleaning and maintaining the sewer system.
  • Reducing infiltration and inflow of stormwater and groundwater into the sanitary sewer through rehabilitating and repairing broken or leaking lines.
  • Enlarging or upgrading sewer lines and pump stations.
  • Expanding the capacity of sewage treatment works and enhancing sewage treatment plant reliability.
  • Eliminating buildup of fats, oils and grease (FOG) from the sewer system.
  • Educating the public on how FOG, wipes and other household products can clog sewer lines.


Is it possible to totally prevent SSOs?

Unfortunately, overflows cannot be prevented entirely. The EPA writes that “a few SSOs may be unavoidable. Unavoidable SSOs include those occurring from unpreventable vandalism, some types of blockages, extreme rainstorms, and acts of nature such as earthquakes or floods.”

What can I do to help prevent SSOs?


  • Keep drains and sewers clear of FOG, which coagulate in sewer pipes and can cause blockages. FOG should never be poured down sink drains or into toilets or garbage disposals. Instead, pour FOG into a covered disposable container and put it in the trash.
  • Though baby and facial wipes may claim to be “flushable,” they often do not break down as they travel through household pipes and the sanitary sewer system and can lead to clogs and SSOs.
  • Some older homes, businesses and developments have improper connections to the sewer system, which include, but are not limited to, roof downspouts, sump pumps, area drains and similar features. Check around your house to ensure storm water is not draining to the sanitary sewer system. If you are concerned that you may have an improper connection, contact the Service Authority immediately.
  • Make sure your sewer cleanout cap is securely fastened. Cleanouts are access points for the sanitary sewer line that serves your home.