Public Works and Environmental Services

Fairfax County, Virginia

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12000 Government Center Parkway
Suite 448 Fairfax, VA 22035

Christopher S. Herrington,
Director

Tysons Wastewater Conveyance Systems Modifications Project

Project # WW-000032-002

Project Update: December 9, 2022

The survey crews are now working collecting data along the pipeline alignments.

Project Background

The Fairfax County Department of Public Works and Environmental Services, which is responsible for wastewater collection and treatment in Fairfax County, is working on several wastewater infrastructure projects to collect and treat the additional wastewater that is anticipated to come from the northern parts of Fairfax County. The Tysons Wastewater Conveyance Systems Modifications project is one of these projects.

The goal of Tysons Wastewater Conveyance Systems Modifications project is to increase the size of the sewer system to accommodate the planned growth in the northern Fairfax County and to ensure the system continues to provide continuous reliable service to all customers. This project will decrease the risk of wastewater overflows and back-ups during periods of high wastewater flows by diverting flow from existing infrastructure.

Since it can take five years or longer to effectively plan, design, construct, and bring these types of facilities online, the county is working now to stay ahead of the development. This project is in the Difficult Run Watershed. This project is located in the Hunter Mill and Providence Magisterial Districts.

Project Description

The county has been studying future flow projections for the northern Fairfax County and compared them to the capacity of the existing pipes, pump stations, and treatment capacity. The study showed that facilities in the northern Fairfax County have insufficient capacity to handle future flows. The study concluded that the wastewater flows from northern Fairfax County can be pumped to the Noman Cole Pollution Control Plant, the wastewater treatment facility in Lorton VA, which has available treatment capacity for these future flows. To transport the flows to treatment facility, the county has been developing and evaluating three main components of the transmission infrastructure: a gravity sewer pipeline; a pump station; and a force main (a pressurized pipeline).

Illustration - Tysons Pump Station
The existing Tysons Dodge pump station will be replaced.
 

Gravity Sewer

To accommodate the higher volume of wastewater the county anticipates, the county evaluated eight potential routes for a new gravity sewer pipeline based on a set of criteria. The criteria included community impacts (residential, commercial, traffic, parking, noise/dust), environmental impacts (streams, parks, trails, trees, wetlands, open spaces), costs (construction, maintenance, and operation) and others.

The pipeline route, the county selected, provides approximately two miles of new sewer pipe in the Tysons area to transport wastewater from individual customer connections to the new pump station.

Pump Station

The existing pump station must be replaced with a new, larger facility. The current station was constructed in 1969 and had the ability to pump one million gallons per day of wastewater. The new pump station will pump up to 25 million gallons per day to the Lorton wastewater treatment facility.

The new pump station will be located in the northern part of the Tysons area in a low-lying area in the vicinity of the Spring Hill Metro Station near the existing pump station. The new pump station building will be a state-of the-art facility with energy efficient pumps, odor and noise control, and emergency back-up power. The building will be designed to fit into the community with appropriate architectural treatment.

Force Main

Ten potential routes for the force main to carry wastewater to the Lorton VA wastewater facility for treatment were evaluated.

The criteria for evaluating the force main pipeline routes were the same the gravity pipeline criteria and included community impacts (residential, commercial, traffic, parking, noise/dust), environmental impacts (streams, parks, trails, trees, wetlands, open spaces), costs (construction, maintenance, and operation), while other criteria such as pipeline pressure were specific to the force main. The selected route provides 5.5 miles of new pipeline to transport wastewater.

Project Location

map - tysons west wastewater system enhancements

 

Timeline

Planning Spring of 2020 – Spring of 2022
Design Spring of 2022 – Summer of 2025
Construction Completed Summer 2028

 

What to Expect

Area residents, business owners, and other key stakeholders located close to the selected pipeline routes will have an opportunity to hear presentations and make comments on the selected route. The county will publish a summary of responses to questions on this website. Once that’s completed, a quiet period for design and permitting will follow.

It is estimated that construction impacts will last for only a few days in one location along the pipeline as the work progresses quickly. Impacted stakeholders will be notified in advance of construction activities. Some of the construction will be performed using trenchless methods to reduce the impact to roads and traffic.

In addition, stakeholders located near the pump station site will receive information about the pump station facility construction and any potential impacts that may have on them.

Project cost and funding source

The engineer’s preliminary opinion of the cost for this project is $110 million and it is being fully funded through sewer service charges from existing customers and availability charges, which are one-time fees for the initial connection to the system. No tax dollars are funding these improvements and there will be no impact to the rates existing customers pay for their wastewater service.

Presentations to the community

View the Preliminary Engineering Report

Recording of Tysons West Public Meeting - May 10, 2022

Contact

For more information, please contact the project manager Agata Fallon.

Frequently Asked Questions

1. What is the Tysons Wastewater Conveyance Systems Modifications Project?

The Tysons Wastewater Conveyance Systems Modifications (Tysons West) project is a Fairfax County Department of Public Works and Environmental Services wastewater facilities expansion project that will provide facilities for conveyance of increasing wastewater flows to treatment facility in Lorton Virginia. This project will provide new: collection system piping, pump station and force main (pressure pipe) to transport the wastewater.

2. What is the goal of the Tysons Wastewater Conveyance Systems Modifications Project?

The Tysons Wastewater Conveyance Systems Modifications project will increase the size of the sewer system to accommodate the planned growth in the northern Fairfax County and to ensure the system continues to provide continuous reliable service to all customers. By diverting flows from existing infrastructure, this project will decrease the risk of wastewater overflows and back-ups during periods of high wastewater flows.

3. Who benefits from this project?

All system users (residents and businesses within the County’s service area) will benefit from this project, as they will continue to have a resilient and robust wastewater system, without overflows or backups. The local environment also will benefit from the reduced risk of sewer overflows and system failures.

4. Who will be impacted by this project?

Property owners, residents, and businesses nearby will be impacted by the construction for a time. This will include commercial and residential properties as well as Fairfax County Public Schools, Virginia Department of Transportation, Fairfax County Park Authority, NOVA Parks, and utility companies. Some levels of impact are unavoidable for such a large infrastructure project. Fairfax County will reach out to those impacted to explain the impacts and work to develop strategies to reasonably mitigate them.

5. How were the selected pipeline routes chosen?

Many routes, all of which had challenges and create impacts, were evaluated by the Fairfax County Department of Public Works and Environmental Services in consultation with its engineering consultant, CDM Smith. Several evaluation criteria were considered, including:

  • Community
  • Hydraulic factors
  • Constructability
  • Environmental
  • Land rights
  • Utilities
  • Costs
  • Stakeholders

It is our goal to find a route within this corridor that creates the least impacts for the least amount of people.

6. Are details of the selected routes available?

We have identified a corridor for the pipe alignments and are in the process of gathering information about the existing conditions within the corridor and doing field surveys. We will be providing updates on this website as the project develops.

7. How will traffic be impacted in the project area?

Pedestrian, cyclist, and vehicle safety is a key consideration in all design decisions, however, at this time we are uncertain whether any portions of roadways will be closed and, if so, for what duration. We will work closely with VDOT to develop Maintenance of Traffic plans, to transportation modes. This is a required part of design development and will follow other similar roadway projects in the area. When the plans are completed, we will share them.

8. Will any of this construction be done at night?

At this early stage, no decision has been made about night construction timing or construction methods. We will work closely with stakeholders, including but not limited to, impacted property owners, VDOT, other utility providers, and the contractor to develop the best construction schedule to minimize impact of construction activities.

9. Has this project been coordinated with parks and trails?

Yes, we will be coordinating the design with the Fairfax County Parks Authority and NOVA parks. We coordinate to minimize impacts and maintain trail access or provide temporary trail routes where needed.

10. Why were force main alternatives through Vienna eliminated from consideration?

Vienna is an independent jurisdiction. Permits and permissions would be needed from Vienna for these alternatives as Fairfax County has no existing assets in these areas. Multiple attempts were made to move toward acquiring these rights, but ultimately, the Town and County were unable to negotiate a donation or sale of these rights. Thus, the alternatives were dropped from further consideration.

11. How is the planning and study of the various projects integrated and coordinated with each other?

Fairfax is required to operate the sewer system in accordance with federal permit requirements. This permit requires that the sewer system be constantly maintained and monitored for compliance. This includes evaluating the system for any improvements needed to properly operate the existing system and evaluate needs for expansion and growth. The Tysons program projects were conceived as a result of these evaluations. Individual projects in the program were developed in the context of the overall system goals and project specific needs and have been coordinated in the context of their fit and implementation into the overall sewerage system.

12. Was the Tysons West alternate 7 force main evaluated in the context of any potential to reduce the extent of Accotink Gravity sewer capacity improvements required?

During development of alternatives for each individual project, the recommendations for each were also evaluated in terms of the improvements to the overall sewerage system. In the context of this overall coordination, it was determined that the alternate 7 higher head, longer force main did not provide any overall significant benefit over the selected alternative force main with lower head, shorter force main, and an incremental gravity pipe increase in the area north of the force main connection where improvements to the pipe capacity will be required.

13. Can you describe the process of how all the alternatives in the report are evaluated to determine the selected alternative?

Alterative concepts are developed to address the needs of the project. These alternatives are screened to determine if they are feasible to properly address the needs of the project. Once alternatives were screened to a smaller number of viable alternatives, this subset of alternatives were evaluated and ranked in detail to determine the selected alternative.

14. Would the Fairfax County Governance consider an independent review of the project recommendations?

Current Fairfax County practice is to complete what is known as a Value Engineering (VE) study for projects of this magnitude. These VE studies are done by an independent team of wastewater professionals who are completely independent of any county staff, or design consultants currently involved with the projects. This VE process results in an independent review of the project concepts and results in a series of recommendations for ways to approach the project differently to achieve cost savings.

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