The Fairfax County Board of Supervisors approved a plan this week to pay $8.7 million towards a Silver Line underpass structure on Town Center Parkway from Sunrise Valley Drive to Sunset Hills Road.

The supervisors said in county documents it is crucial to get the underpass built soon rather than try and construct it when Phase 2 of Metro’s Silver Line is already running. The funding will go towards planning the $157 million project.

Fairfax County Department of Transportation staff worked with Metropolitan Washington Airports Authority on the plan, which calls for construction of a four-lane divided roadway under the Dulles Toll Road.

The Town Center Parkway Underpass Rail Support Structure project was part of the Board of Supervisors’ Six Year Transportation Priorities for FY2015 to FY2020, which was approved by the Board earlier this year.

According to FCDOT’s project timelines for the Six Year Transportation Priorities, the Town Center Parkway Underpass Rail Support Structure project is scheduled to begin implementation in FY 2015.

Phase 2 of the Silver Line, which will run from Reston’s Wiehle Avenue to Reston Parkway and Herndon, Dulles International Airport and into Loudoun County, is under construction and expected to open in 2018. Phase 1, which opened in July, runs from Tysons Corner to Wiehle Avene.

Said the supervisors:

The extension of Town Center Parkway from Sunset Hills Road to Sunrise Valley Drive west of Edmund Halley Drive is recommended in the County’s Comprehensive Plan.

This improvement is necessary to achieve the vision of the Reston Transit Station Areas, and enhance connectivity of the overall roadway network.

Constructing the underpass structure beneath an active Metrorail line in the future would cause significant interruption to the rail service. To help eliminate, or at least minimize this disruption as much as possible, the county has proposed to fund the design and construction of the rail support structure as part of the Phase 2 Metrorail project that passes over the future underpass, thus allowing Metrorail tracks to span the future roadway extension.

This work would ensure that Phase 2 of the Silver Line would be supported when the  future underpass is constructed, and limit disruption to Metrorail service during construction of the underpass.