Improving infrastructure millions of travelers rely upon, Metropolitan Washington Airports Authority initiated a $3.4 billion, six-year expansion plan for Dulles International Airport. The Tier 2 Concourse was one of the two major elements in the plan. The other was construction of a two-track automated train system (AeroTrain) to provide passenger transport between the main terminal and midfield Concourses A and B.

Schnabel provided geotechnical, geostructural, and rock mechanics engineering services related to design of the excavation for the AeroTrain’s Main Terminal Station and connections for the future Tier 2 Concourse (Concourse C, replacing existing Concourse C/D). The station is 60 feet below ground, directly adjacent to the Main Terminal, and spans its entire length – 1,600 feet – from west to east. It has four levels: departures, arrivals, security mezzanine, and a 54,500 sf train platform at the lowest level.

Our pre-design and design services encompassed rock mass characterization studies, evaluation of blasting methods for rock excavation, rock pressures for design of support of excavation and permanent building walls, and permanent dewatering for reduction of hydrostatic uplift and wall pressures. To assist designers and contractors with future related development projects, we developed a consolidated geotechnical engineering report that incorporated the results of our and others’ previous investigations.

During construction of the Main Terminal Station, we monitored various instruments to evaluate the effect of excavation and construction on the support system. Tasks included developing an instrumentation plan, specifications, instrument selection and installation criteria, field observation of instrument installations, data collection, and reporting.