Wastewater Collection/Sewer Services

Main Sewage Pumping Station
Main Sewage Pumping Station

DC Water's wastewater collection system consists of the following:

  • Approximately 1,800 miles of sanitary,combined and storm sewers
  • 16 storm water stations
  • 75,000 catch basins and manholes
  • 22 flow-metering stations
  • 9 wastewater pumping stations

The sewers range from 8-inch pipelines to 27-foot arches. In the past, the sewers were generally constructed of vitrified clay, brick, and concrete. Current sewer construction materials typically consist of PVC, ductile iron, and concrete. Force mains are generally constructed of iron, steel or concrete.

While two thirds of the system contains separate sanitary and storm sewers, combined sewers serving both sanitary flow and stormwater drainage are prevalent in the downtown area and in older portions of the service area. Combined sewer overflows (CSOs) occur during certain storm events when the capacity of the combined sewer system is unable to convey the mixture of wastewater and stormwater to the treatment plant. There are presently 53 CSO outfalls listed in the National Pollutant Discharge Elimination System (NPDES) Permit issued by EPA to DC Water.

Inside the Main Sewage Pumping Station
Inside the Main Sewage Pumping Station

As part of the current Combined Sewer Overflow (CSO) Abatement Program implemented in the last decade, there has been an effort to maximize in-line storage and minimize combined sewer overflows to receiving waters. The CSO Abatement Program consists of collection system optimization using inflatable dams, dynamically controlled weirs, outfall gates and other flow regulating devices, sewer separations, and a swirl treatment facility. DC Water is currently in the process of designing the replacement of the first generation of inflatable dams with a more durable version of this technology.

The Northeast Boundary Swirl Facility provides preliminary treatment including disinfection and some solids removal for combined sewage overflows prior to discharge. The facility only functions during wet weather periods. DC Water is in the process of conducting a Performance Evaluation to assess the overall treatment efficiency of this facility.

What can you find in this section?

  • History of Sewer System
    DC Water’s sewer system dates back to 1810.
  • Combined Sewer System
    Find out how DC Water is working to reduce combined sewer system overflows.
  • Sanitary Sewer System
    DC Water's sanitary sewer system includes approximately 600 miles of large interceptor sewers and smaller gravity collection sewers.
  • Catch Basins
    Members of the public may access catch basin locations through the Google Earth application.
  • Potomac Interceptor
    The Potomac Interceptor conveys approximately 50 million gallons per day of wastewater near the Washington Dulles International Airport, along the Potomac River through the Potomac Pumping Station, to Blue Plains for treatment.

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