Combined Sewer System
There are two types of storm sewer systems in the City of Alexandria, a separate sewer system, and a combined sewer system. Separate sewer systems consist of two pipes: one pipe conveys stormwater runoff (rain water) from storm drains to local waterways with little or no treatment to remove pollutants. The other pipe conveys sanitary sewage to a local wastewater treatment plant (operated by Alexandria Renew Enterprises) as shown in the figure below. Most of the City (95% of the land area) is served by separate sewer system.
In contrast, Combined Sewer Systems (CSS) have only one pipe which conveys both sanitary sewage and stormwater to a local wastewater treatment plant. About 540 acres in the Old Town is served by a combined sewer system, which was designed to carry sewage from inside homes and businesses and stormwater runoff from streets, rooftops, and parking lots in a single pipe—a “combined sewer.” During dry weather, all raw sewage flows to the treatment plant operated by Alexandria Renew Enterprises. When it rains, the pipes can become overloaded with polluted stormwater. This mixture of stormwater (about 90%) and raw sewage may overflow into local streams through one of the four permitted outfalls.
Over period of time, much of the combined sewer system has been separated, and only 5% of the City, approximately 540 acres, primarily in Old town is served by Combined Sewer System. The map below shows where remaining CSS is located and the location of remaining four CSOs in the City of Alexandria.
The City’s Combined Sewer System (CSS) is operated under a permit issued by the Virginia Department of Environmental Quality (VDEQ). This permit is authorized under the Clean Water Act and governed by the National Combined Sewer Overflow Control Policy. Under that policy each city must have a Long Term Control Plan to address its CSS. The Environmental Protection Agency (EPA) has developed multiple guidance documents for the National CSO policy including the Guidance for Long-Term Control Plan.
The City’s ongoing operation, maintenance, and monitoring programs insure that the overflows meet all of the regulatory requirements and existing permits.
What is New?
The City of Alexandria has received a 5 year renewal of its permit to operate Combined Sewer System. In 2011, the City applied to Virginia Department of Environmental Quality (VDEQ) for its Virginia Pollution Discharge Elimination Permit, which regulates discharges from the City’s Combined Sewer System (CSS). The City’s Combined Sewer System, a legacy infrastructure built in 19th and early 20th century, is a combination of storm and sanitary sewer systems serving approximately 540 acres in Old Town.
As part of the City’s Eco-City Alexandria initiative, and in coordination with VDEQ, this new permit ensures regulatory requirements are met and the environment is protected. Under the permit negotiated by the City with VDEQ, the City will be updating its Long Term Control Plan (LTCP) over the next three years, and implementing several additional projects to improve water quality in Hunting Creek, Potomac River, and Chesapeake Bay. The LTCP to be developed will identify the strategy, projects, schedule, additional infrastructure investments and long-term impacts on the community and will be implemented no later than 2035. In addition to developing the LTCP, the permit also requires the City to implement several important construction projects within the five year permit cycle. These projects are needed to improve the system and to continue to reduce the impacts.
The City plans to start planning and implementation of several new and expanded initiatives required under the new CSS permit, including the following:
- Update the LTCP within three years from the issuance of the permit.
- Construction projects to improve sewer system performance, and improve water quality.
- Develop and implement green infrastructure pilot projects within the CSS.
- Continue implementing CSS Area Reduction Plan that requires developers to separate sewers in the CSS as redevelopment occurs.
How can residents provide input?
- The City of Alexandria encourages residents to participate in public process for the development of Long Term Control Plan Update over next three years that will help bring long-term improvements to Alexandria’s sewer system infrastructure, improve water quality, and meet new regulatory requirements.
- Input is also sought on the process used to develop the LTCP by sending comments to Lalit Sharma, Division Chief, Office of Environmental Quality, Lalit.Sharma@alexandriava.gov.
Outreach and Presentations
The City held an information meeting and public hearing on the draft CSS permit on August 5, 2013. The agenda, presentation and video recording of this meeting can be found below.
The City is also providing informational meetings, including neighborhood and civic associations.