The Purple Line project is a 16-mile light rail line that will extend from Bethesda in Montgomery County to New Carrollton in Prince George’s County. It will connect to four branches of the Metro rail system at Bethesda, Silver Spring, College Park and New Carrollton, as well as all three MARC commuter rail lines, and Amtrak. Twenty-one stations are being constructed along the alignment. Once complete, the light rail will operate mainly in dedicated or exclusive lanes, allowing for fast, reliable transit operations.
The project also includes the completion of the Capital Crescent Trail between Bethesda and Silver Spring, the completion of the Green Trail along Wayne Avenue to Sligo Creek Parkway, and the construction of a bike path through the University of Maryland Campus. Close coordination is occurring with the Washington Metropolitan Area Transit Authority, Montgomery and Prince George’s counties, the Maryland-National Capital Park and Planning Commission, State Highway Administration, and local municipalities in the project area.
Traylor’s underground group has constructed the 1,208-foot cut and cover/sequential excavation method (SEM) tunnel, one underground station, and a deep shaft/cavern in rock. Traylor’s heavy civil group is providing structures expertise on the construction of 16 bridges that will be replaced or reconstructed along the alignment.
The 36-foot-wide, 29-foot-tall single tube tunnel will accommodate both trains and all supporting equipment. The entry/exit ramp was constructed by open cut and the mined tunnel by SEM. A bulldozer with a ripper was utilized until hard rock was encountered. At that point, blasting was utilized 60 to 120 feet at a time. In the Plymouth tunnel, the team has completed invert concrete. Waterproofing of the arch was followed by installation of the secondary shotcrete liner.
At Bethesda Station, excavation of the shaft is complete and installation of waterproofing and cast-in-place concrete liner for the shafts is ongoing. Once complete, excavation of the cavern in rock by drill and blast will begin. Excavation, waterproofing, and pouring of the base slab is complete at Manchester Place Station. Current work includes waterproofing the wall and cast-in-place concrete of the walls.
Working together with partners on the fit-out of the Bethesda Station and the Bethesda enclosed trainway allows other team members to focus on the construction of critical structures along the CSX corridor in Silver Spring. With 96 percent of the design complete and most of the right-of-way acquisitions finalized by the owner, major construction activities will accelerate throughout 2020.