Linking the region’s key activity centers, the Dulles Corridor Metrorail project extends Washington’s Metrorail system 23 miles to serve growth and development beyond the completed regional system. Schnabel is the geotechnical engineer of record for Phase 2, which will extend the corridor 11.4 miles west from the Wiehle-Reston East Station through Washington Dulles International Airport and into Loudoun County.

Phase 1, known as the Silver Line, opened in July 2014 and preliminary construction for Phase 2 began the same year. The $2.78 billion Phase 2 investment encompasses six stations and the infrastructure necessary to power the system, manage stormwater runoff, and realign major roadways. Five of the new stations will be built at ground level, but the sixth, at the airport, will be an aerial station.

We developed foundation design approaches tailored to aerial guideway drilled shafts, stations, and bridges. Our specialized testing processes and more than 1,500 test borings made during subsurface exploration of the six sites informed these recommendations. We mobilized up to eight drill rigs at a time and managed more than 30 workers to meet the demanding drilling schedule. Coordination of this effort, along with traffic control and utility clearance, was a challenge we met head on by assigning a full-time site manager.

Additional design phase tasks included assessing the pavement of adjoining roadways, evaluating rock and groundwater impact on the design of stormwater management facilities, and providing design options when remedial actions were required. Our construction phase services extend to consultation on foundations – including inspections to confirm design capacities – earthwork, subgrade stabilization, pavements, groundwater control, and stormwater management.