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 Mar 19, 2018 at 5:32 PM

Frequently Asked Questions

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

Long Term Control Plan Update

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.   

Community Engagement

The City continues to engage community partners in the development of the Long Term Control Plan Update. 

Beginning Friday, March 23, the Combined Sewer System Long Term Control Plan will be available on the City’s website for a 30-day public comment period. The public is invited to view the plan and submit comments online. The comment period ends on April 22.

Community members will also have the opportunity to provide in-person feedback at a public meeting on April 5, from 7 to 9 p.m., at AlexRenew (1800 Limerick St.). The City and AlexRenew will present the draft plan and solicit comments and feedback.

The City of Alexandria is on track to comply with a 2017 state law requiring that remediation of its four combined sewer outfalls be completed by July 1, 2025. As part of the process, the City is required to update the  Long Term Control Plan, which includes an implementation schedule to meet the 2025 deadline, to be filed with the Virginia Department of Environmental Quality.  

Read more about community engagement efforts.

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

The City has been briefing the Virginia General Assembly with respect to how it is moving forward to address the new legislative mandate. A copy of the City's December 4, 2017 presentation to the State Water Commission is provided here


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. 

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.