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 Apr 10, 2017 at 2:05 PM

What's New

On April 7, 2017 Mayor Allison Silberberg, on behalf of the Alexandria City Council sent a letter to Governor Terence R. McAuliffe expressing City’s commitment to taking all necessary corrective actions for its CSO outfalls as quickly as possible.  (Attachment)

On February 21, 2017, City Manager Mark B. Jinks presented City Council with the proposed budget for Fiscal Year 2018. This proposed budget includes $390 million in funding to address all four the outfalls in the City's Combined Sewer System in order to meet recent legislation that was passed as part of the Virginia Legislative Assembly earlier this year. This legislation requires the City to address all combined sewer outfalls at an accelerated schedule compared to the schedule developed in the City's Long Term Control Plan Update that was submitted to the Virginia Department of Environmental Quality in December 2016. More information about the proposed budget can be found here.

Current Status of the 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. This document incorporates VDEQ's comments on the draft document that was submitted in August 2016. In addition, this final document incorporates City Council's action at the November 9, 2016 City Council Legislative Session to accelerate addressing the combined sewer outfall that discharges into Oronoco Bay. This acceleration called for the following with respect to the Oronoco Bay outfall:

  • Committing in the Long Term Control Plan Update to perform a feasibility study during the upcoming permit cycle (2018-2023), 14 years ahead of current draft plan.

  • Committing in the Long Term Control Plan Update to perform an assessment starting in 2026, six years ahead of current plan.

  • Enhanced funding in the CIP for sewer separation and green infrastructure.

City Council approved the option to accelerate addressing the Oronoco Bay outfall. Staff is in the process of updating the draft Long Term Control Plan Update consistent with this option, along with other minor edits on the draft report in response to comments received from Virginia Department of Environmental Quality.  More information can be found on the City Council Docket.

The City Council Public Hearing on the framework of the Long Term Control Plan Update took place on May 14, 2016. More information, including the presentation staff provided to Council, is available at the City's Dockets and Webcasts webpage. At the public hearing, City Council authorized staff to submit the Long Term Control Plan Update document to the Virginia Department of Environmental Quality (VDEQ). This document was submitted to VDEQ as a draft in August 2016 for their review and approval.

The following documents below provides a summary on the City's proposed Long Term Control Plan Update: 

Proposed Long Term Control Plan Brochure

Proposed Long Term Control Plan Summary Document

Ad Hoc Combined Sewer System Plan Stakeholder Group

On June 23, 2015, Alexandria City Council approved a resolution to establish an Ad Hoc Combined Sewer System Plan Stakeholder Group (Stakeholder Group) to assist in monitoring the development of the Long Term Control Plan Update for the City’s combined sewer system. This Long Term Control Plan Update is required by the Virginia Department of Environmental Quality (VDEQ) to meet new permit requirements and is due to VDEQ by August 23, 2016. The Stakeholder Group provided input to staff on a proposed recommended plan to VDEQ, including considerations on the City’s budget, meeting environmental goals, and minimizing impacts to the community. The Stakeholder Group convened its final meeting on Thursday April 7, 2016 at 7:00 PM. Following the final meeting, the Stakeholder Group submitted a memorandum to the Mayor and members of City Council summarizing their input during the development on the Long Term Control Plan Update and recommendations for moving forward.  

Meeting Materials


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.

CSS Separate Sanitary and Stormwater Systems 

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 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 

In 2013 the City of Alexandria received a 5-year renewal of its permit to operate its CSS from the Virginia Department of Environmental Quality (VDEQ) through the issuance of a Virginia Pollution Discharge Elimination Permit, which regulates discharges from the City’s CSS through the CSO outfalls.   

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.

In addition, the City is required to submit a Work Plan to VDEQ which details the process and schedule for how the City will prepare the update to the LTCP, including public participation. The Work Plan was submitted in May 2014 and approved by VDEQ in July 2014. The City has been submitting to VDEQ a series of technical memoranda throughout the Long Term Control Plan Update process in accordance with the approved Work Plan. Technical memoranda submitted to VDEQ to date include the following:

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. Comments and input should be provided to Erin Bevis-Carver, P.E., Sanitary Section Lead, Stormwater and Sanitary Infrastructure Division, Transportation and Environmental Services at 703.746.4154 or at

Throughout the development of the Long Term Control Plan Update, input and feedback were provided by the public to the City at the public meetings, City Council public hearing, CSS Stakeholder Group, and through the use of AlexEngage, the City's online forum for civic engagement. Public input from the meetings is provided on this page. Feedback from AlexEngage can be found here.   

Outreach & Presentations

The City has been holding a number of public information meetings related to the Combined Sewer System Long Term Control Plan Update and the Combined Sewer System Permit issued by the Virginia Department of Environmental Quality in August 2013. The agenda, presentation and video recording of these meetings can be found below. 

April 21, 2016 - A public meeting was held that presented the proposed framework to the community. Information related to the April 21st meeting, including the presentation, can be found below.

June 18, 2015 - A public meeting was held that explained the progress to date the City has made in developing an update to its Long Term Control Plan to comply with new regulatory requirements. Information related to this meeting, including the presentation, can be found below.

February 15, 2015 - A public meeting was held o present information related to its ongoing combined sewer system planning efforts that are required to meet new water quality regulations in order to reduce the impacts of combined sewer overflows on receiving waterways. The City is required to update its Long Term Control Plan to meet the new regulations and must submit it to the Virginia Department of Environmental Quality by August 2016. The presentation, video recording, informational handout, and feedback form related to this meeting can be found below.

August 5, 2013 - A public meeting was held to present the draft CSS permit and inform residents how to provide comments on the permit to the Virginia Department of Environmental Quality.

The City is also providing updates to City Council throughout the planning process.   

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.