Richmond VA > Public Utilities > Combined Sewer Overflow (CSO) Project

Last Updated: 2019-11-04

What is a Combined Sewer Overflow?

A Combined Sewer Overflow (CSO) is a discharge of untreated storm and wastewater from a combined sewer into the environment. CSOs typically occur when combined sewers fill up with too much water for the system to handle, most often during heavy rains, and the excess water is released into a stream or river.

Richmond, Virginia's CSO system is the largest in the state of Virginia. The area serviced by Richmond's CSO system is approximately 12,000 acres.

See an animated depiction of how a combined sewer overflow system works.

When do CSOs occur?

During dry weather, combined sewer systems carry all the sanitary flow to wastewater treatment plants. During times of rainfall, however, the amount of rainfall adds to the amount of flow going to the treatment plant. This heavier flow is greater than the capacity of the combined sewer system. When the flow exceeds, the capacity, the excess flow is discharged directly to the river at various overflow points in the sewer system. In Richmond, the major overflow points are found on the banks of the James River and Gillies Creek.

Richmond's CSO system is financed through state and federal grant funding, state low-interest loans, and rate payers.

What are CSO outfalls and where are they located?

There are 25 CSO outfalls located at various points along the James River within the city's CSO area.

Map showing the location of CSO areas.

Information regarding flow conditions of the James River

Combined Sewer Overflow Monthly Reports

In 2020, the City of Richmond finished installing new monitoring technology with sensors and meters in the combined sewer system. The meters will tell us in real time when an overflow occurs and how much volume is discharged. Because we do not have an entire calendar year with the real time data, we will use modeled data for the 2020 reports. Beginning in 2021, the City will use the metered flows and volumes in its overflow reports.

Combined Sewer Overflow

November 2020

October 2020

September 2020

August 2020

July 2020

June 2020

May 2020

April 2020

March 2020

February 2020

January 2020





Contact information for Combined Sewer Overflow (CSO) Project

By email: You can receive CSO Advisories in your inbox by subscribing to the CSO Public Notification mailing list. Subscriptions are free and easy to setup.

To subscribe to receive email notification of CSO Outfalls.

To unsubscribe from receiving email notification of CSO Outfalls.

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Contact Information:

Public Utilities
City of Richmond
900 E. Broad St.,
Room 115
Richmond, VA
23219 USA
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Phone: (804)646-4646
Interested in learning about how our award winning water is treated and transported to your home or how the water that leaves your home is treated and placed back into the James River? Request a tour of our Water Treatment Plant or Wastewater Treatment Plant. Click here to fill out the form.

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