Project Profile
U.S. Department of Transportation Headquarters Building – Adjacent Construction Monitoring
Washington Metropolitan Area Transit Authority (WMATA)
Washington, DC
The new U.S. Department of Transportation Headquarters Building at the Southeast Federal Center is within the bounds of the Washington Navy Yard in Washington, DC. WMATA Green Line tunnels between the Navy Yard Station and the Anacostia Station lie under the building foot print. The project required an excavation over the subway tunnels, and FEA provided instrumentation and monitoring services for the tunnels and associated structures in accordance with the requirements of WMATA’s Adjacent Construction Design Manual.
FEA provided an instrumentation program utilizing six robotic theodolites mounted along the tunnel wall that would sight and locate target prisms around the tunnel cross section at 25-foot intervals along 2,100 feet of the monitored section of the tunnels. The theodolites, controlled by two computers placed inside the tunnels, were mathematically linked to a control network and provided a direct measurement of the change in the tunnel cross section including the rail bed, making approximately 430 direct measurements hourly of the tunnel cross section using six instruments. This system reduced potential measurement errors as well as labor costs compared to normal manual data collection techniques. The automated system was monitored remotely from our office with data samplings posted on our website for review. Predetermined threshold values allowed FEA to alert the contractor and owner of movement trends during excavation and construction.
Scope Items:
- Design and install an array of instruments to allow detection of movement or settlement of tunnel walls and track rails
- Automated remote data collection at FEA office
- Real time data sampling and posting to website for easy access and review by FEA engineers and the client
- Predetermined thresholds for movements allowing immediate contingency response by contractor to site conditions