Public Works and Environmental Services Alert:
Due to development of the Mosaic area and population increase, the current pipe size is at capacity and must be increased to avoid potential Sanitary Sewer Overflows. As the gravity sewer pipe is located directly under the mail-truck loading zone for the United States Postal Service, Fairfax County has coordinated closely with USPS to design a gravity sewer capacity upgrade that will be constructed using Pilot Tube Microtunneling.
Construction implementation using Pilot Tube Microtunneling will consist of drilling bore holes and tunneling underneath the ground to have the least amount of impact to USPS on the ground surface. The construction project will utilize two receiving pits (located at Manhole 60 in the PNC bank parking lot across from Caboose Brewery, and at Manhole 58 on USPS property). The jacking pit where the pilot tube microtunneling machine will bore from is located at Manhole 59 at the Mail Carrier Facility.
The project is located at the Merrifield United States Postal Service Office off Route 29 near the Mosaic Town Center. The pipes that are being upsized are a chokepoint that is at capacity and receives wastewater flow from both the Mosaic Town Center and the Dunn Loring Metro Station area.
Flow from the Dunn Loring Metro station area and flow from the Mosaic Town Center flow into Manhole 60 downstream to Manhole 59, and into Manhole 58. The pipes between these three manholes are where the chokepoint in the system is located and the pipe size needs to be increased.
The flow of wastewater flows from Manhole 60 in the PNC Bank parking lot downstream to Manhole 59 located in the USPS Mail Carrier Facility parking lot to Manhole 58 by the USPS Engineering Building.
This project is finally under construction after undergoing years of a rigorous design and property rights acquisition process in which the USPS and Fairfax County Wastewater Design and Construction Division worked closely together to mitigate potential impacts to the USPS.
Construction started early 2025 and is expected to conclude in the Fall of 2025.
You can expect to see green construction fences around the 3 manholes that are integral to the project as well as some construction fencing around manholes and pumps located directly upstream and downstream of the project.
You can expect USPS operations and mail delivery to continue functioning as usual.
Fairfax County Wastewater Design and Construction Division has worked closely with Caboose Brewery to lessen our impacts as much as possible. You will see a construction barrel covering a manhole lid that our team will need access to on a frequent basis, as well as a steel plate covering the area where we have underground piping that is necessary for us to pump the flow of wastewater around Manhole 60 as we construct the upgraded system.
You might also see temporary bypass pumps behind our green construction fence, which one of our crew members will be watching closely 24 hours a day 7 days a week when these pumps are in operation.
The Construction Cost is ~$4 million and comes from the Project Fund 690-C69300, Project Number WW-000032-009.
For more information, please contact the project manager Lizzy Merin, or call the Wastewater Design and Construction Division at 703-324-5111 TTY 711.