Public Works and Environmental Services Alert:
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.
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).
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.