Combined Sewer System

The City's combined sewer system comprises approximately 540 acres and is located in the Old Town area. During most wet weather events, combined sewage (mixture of wastewater and stormwater runoff) discharges through one of four outfalls into receiving waterways. The City is developing a plan to reduce the impacts of combined sewer discharges on the environment. More information about the City's combined sewer system and current planning efforts is provided below.

Page updated on Nov 17, 2017 at 4:19 PM

Frequently Asked Questions

View answers to frequently asked questions about the City's combined sewer system remediation projects.

Community Engagement

 The City held a public information meeting on Tuesday, May 30, at 7 p.m., to share information about how the new project deadline impacts the Combined Sewer System Long Term Control Plan Update submitted to the Virginia Department of Environmental Quality in December 2016. A copy of the staff presentation and a link to the video recording of the meeting are below. A summary of the meeting's question and answer period will be made available soon.

Read more about community engagement efforts. In addition, please see Ad Hoc Combined Sewer System Plan Stakeholder Group on this page (below) with respect to ongoing community engagement. 


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).

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 combined sewer outfalls.

CSS Separate Sanitary and Stormwater Systems CSS Combined Sewer System

The City's Combined Sewer System (CSS), 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. The map below shows where the City's CSS is located and the location of its combined sewer overflow (CSO) outfalls.

Overview Map of Combined & Sanitary Sewer System 

  Read more about the history of Alexandria's combined sewer system. 

Long Term Control Plan Update

The City submitted the Long Term Control Plan Update to the Virginia Department of Environmental Quality (VDEQ) for approval on December 2, 2016. As part of the 2017 Virginia Legislative Session, legislation was passed and signed by the Governor, that requires the City to revise its 2016 Long Term Control Plan Update to meet the 2017 legislation. The legislation requires the City to remediate all of its combined sewer outfalls, requires that construction of future combined sewer infrastructure projects begin no later than July 1, 2023 and that construction of these projects be completed by July 1, 2025. The City is currently in the process of revising its plan and will be providing updates on the development of the plan, along with seeking input, as part of the Ad Hoc Combined Sewer System Plan Stakeholder Group. This group will meet Fall 2017 through Spring 2018 as the plan is developed. The City intends to submit its revised Long Term Control Plan Update to VDEQ by June 1, 2018. The new legislation requires VDEQ to determine, by July 1, 2018, what actions are required by the City in order to comply with the legislation. For more information on the Long Term Control Plan Update, please contact Erin Bevis-Carver, P.E., Civil Engineer IV at 703.746.4154 or

Read more about the Long Term Control Plan Update.   

Ad Hoc Combined Sewer System Plan Stakeholder Group

On June 13, 2017 Alexandria City Council approved a resolution to reconvene the Stakeholder Group to assist in monitoring the development of the Long Term Control Plan Update for the City of Alexandria’s combined sewer system. The Stakeholder Group will provide input on a final recommended plan to the Virginia Department of Environmental Quality (VDEQ), including considerations on the City’s costs, meeting environmental goals, and minimizing impact on the community. The first meeting of the reconvened Stakeholder Group was held on Thursday, October 12, 2017. A copy of the agenda and presentation is below. A meeting summary will also be provided approximately one week following the meeting. The next meeting will be held in November 20, 2017 7-9pm at the Charles Houston Recreation Center (901 Wythe Street) in the seniors room. 

November 2017 Meeting

Stakeholder Group Nov 2017 Presentation

October 2017 Meeting

Stakeholder Group Oct 2017 Agenda

Stakeholder Group Oct 2017 Presentation

Stakeholder Group Oct 2017 Meeting Summary

Read more about the Ad Hoc Combined Sewer System Plan Stakeholder Group. 

Combined Sewer System Annual Reports

As part of the City's VDPES permit for its combined sewer system, the City must submit to VDEQ an annual report on operation and maintenance activities in the combined sewer system by March 31st of each year.  Annual reports for Calendar Year 2013 and subsequent years are provided below.