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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 approximately12,000 acres.
See an animated depiction of how a combined sewer overflow system works.
When do CSO’s 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.
Like the City itself, Richmond’s CSO program has a rich history having begun back in 1970. Click here for a timeline of Richmond’s CSO Control Program.
Richmond’s CSO system is financed through state and federal grant funding, state low-interest loans, rate payers.
What are CSO outfalls and where are they located?
There are 29 CSO outfalls located at various points along the James River within the City’s CSO area. Click here for a chart showing the location of CSO areas.
Update for September 2009 CSO Overflow Reporting.
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