DC Water and Sewer Authority

CSO History

Similar to many older communities in the Mid-Atlantic, Northeast, and Midwest portions of the country, a portion of the District of Columbia is served by a combined sewer system. Approximately one-third of the system is combined, mostly in the downtown and older parts of the city. In dry weather, the system delivers wastewater to the Blue Plains Wastewater Treatment Plant. In wet weather, rain water also enters the system, and if the conveyance capacity of the system is exceeded, the excess flow spills into the waterways of the District of Columbia. This discharge is called Combined Sewer Overflow (CSO). There are 53 permitted CSO outfalls in the District.

Along with a few smaller CSO projects, DC WASA is currently engaged in implementing a Long Term Control Plan (LTCP) for CSOs that discharge to the Anacostia River, Rock Creek and the Potomac River. The schedule for completing the LTCP spans over a 20-year period that ends in 2025 and is included in a Federal Consent Decree between the United States, the District Government and DC WASA. The benefits of our twenty-year plan are significant. When fully implemented, combined sewer overflows will be reduced by a projected 96 percent (98 percent on the Anacostia River) resulting in improved water quality and a significant reduction in debris on our national capital's waterways. In addition, DC WASA's clean-up efforts on the Anacostia River are a key cornerstone of the District's plan to redevelop both sides of the river, including the new baseball stadium and proposed retail development and affordable housing among other projects.

The federal consent decree was entered by the court in March 2005. Projects to control CSOs to the Anacostia River are at the top of the court ordered schedule and DC WASA has recently completed a draft final Facility Plan for these projects. The Facility Plan includes a Summary Report and detailed implementation schedule which DC WASA has submitted to EPA as required by the consent decree. DC WASA is now moving forward in the design and construction phases of the Anacostia River projects according to the detailed implementation schedule submitted to EPA. A recent Court decision from an environmental group's lawsuit involving the interpretation of Total Maximum Daily Pollutant Load (TMDL) measurement may have a potential impact on the LTCP implementation schedule, as we ensure that the Plan we undertake can achieve the goals and requirements of the District's water quality standards which are the bases for the LTCP. DC WASA continues to work with EPA to clarify and resolve this issue.

The plan includes a variety of improvements throughout the District:

• increase excess flow treatment capacity at Blue Plains;
• construct a ten-mile main tunnel system to control Anacostia River overflows, three miles of branch tunnels to relieve surface flooding and a tunnels dewatering pumping station, with project completion in 2025;
• construct a three-mile tunnel system to control Potomac River overflows and a lift station, with facility planning to begin in 2015 and project completion in 2025; and
• construct a mile long tunnel system to control Piney Branch/Rock Creek overflows, with facility planning to begin in 2016 and project completion in 2025.

Construction is well underway with completion of projects that were included in the settlement of a lawsuit against DC WASA regarding implementation of the federal CSO Nine Minimum Controls program. These projects, which were previously budgeted and planned by DC WASA prior to the lawsuit, have reduced combined sewer overflows by almost 36 percent. We are also underway with engineering to separate additional combined sewer areas in Anacostia and Rock Creek. Additionally, we are completing studies to add Low Impact Development (LID) at several DC WASA facilities. We have undertaken the rehabilitation of our major pumping stations to increase their capacity: three of these stations are in the construction phase with construction to be complete in FY 2009, while the fourth (Poplar Point Pumping Station) is still in the design phase with construction scheduled to be completed by FY 2011:

Potomac Pumping Station Rehabilitation

provides for replacing pump motors, motor controls, adding variable speed drives, upgrading the electrical system and electrical feeders, and modifying the existing wet-wells and influent channels. The rehabilitation of the pumping equipment has been completed and placed in service. Completion of this station is expected in FY 2009.

Main & O Street Pumping Stations Rehabilitation

Provides for rebuilding and upgrading sanitary pumps, upgrading electrical and ventilation systems, replacing screens and, installing a screening handling system, and installing odor control systems. Completion of this station is expected in FY 2009.

East Side Pumping Station Rehabilitation

provides for a new, above-grade pumping station. The new station is operational.

Poplar Point Pumping Station Rehabilitation

Provides for improvements that include replacement of the pump motors and controls and rehabilitation of the pumps, structural and architectural repairs, HVAC upgrades, the addition of an odor control system, and electrical and lighting upgrades. Design of the station is currently 80% complete.

Northeast Boundary Swirl Facility

Provides for a partial rehabilitation of this facility including the replacement of the chemical feed systems, partial replacement of the electrical system and the replacement of other components damaged by flooding and chemicals. The design phase of the project has begun.

DC WASA Low Impact Development Projects

Project developed to control wet weather related pollution from DC WASA owned facilities as part of the agreement for the LTCP. LID technology will be evaluated for it's effectiveness in controlling storm water runoff and improvement in water quality.

Rock Creek CSO Projects

These are early action item projects constructed to lower the discharge of combined sewer overflows through regulator adjustments at several outfalls and a separation of sanitary and storm water at permitted CSO outfalls 031 037, 053, and 058.

Outfall Sewer Rehabilitation

This project provides for the rehabilitation of approximately 20,000 feet of the influent sewers to Blue Plains AWT to ensure reliable conveyance of 1076 mgd by April 2011. Inspections of the large diameter sewers which convey wastewater from the pumping stations to Blue Plains revealed significant corrosion and exposed reinforcing steel in portions of the pipes. Engineering analyses determined that the conduits could not carry 1076 mgd due to their condition. As a result, this project will rehabilitate approximately 4 miles of the Outfall Sewers. In accordance with the decree, DC WASA has requested approximately a 4 year extension to 2011 to convey 1076 mgd until the rehabilitation project is complete.

Additional projects within the combined sewer area include:

Main & O Pump Station Intermediate Upgrade

This project reflects work originally anticipated to be completed later in the ten-year plan. However, a small portion of the work was removed from the original upgrade project and has been brought forward in this new project along with some other needed work to provide for needed replacement of storm water pumps and various sluice gates and gate valves at the Main and O Street Pumping Stations.

Combined Sewers Under Buildings

This project has been added to rehabilitate combined sewers located under buildings citywide. This project is a result of the highest priority recommendations from the sewer assessment. Other activities included in this project are cleaning, pre and post CCTV, sealing joints and repair of offset pipe.

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