A retail and dining haven, CityCenterDC is a mixed-use development offering 2 million sf over five city blocks on the site of the former convention center. The $250 million Conrad Hotel, a Hilton luxury brand, anchors the second phase of development. The 10-story, 360-room property featuring 30,000 sf of high-end retail and a 400-car garage opened in February 2019.

Architect of record HKS, Inc. selected Schnabel Engineering DC (SEDC)* as geotechnical engineer of record in part because of our knowledge of the site. In 1979 we performed a subsurface exploration for the convention center, and we conducted subsurface investigations for Phase 1 of CityCenterDC in 2007. We retained the boring data and laboratory test results from both jobs and referenced that information for this project.

For this phase, we conducted a subsurface exploration and provided soil laboratory testing services that informed our recommendations for seismic site classification, shallow and deep foundation system alternatives, support of excavation, foundation construction sequencing, and special site conditions. We factored into our approach the Phase 3 development of the adjacent parcel to the east and the relationship between the hotel and any future building(s).

Due to heavy loads and sequencing of adjacent construction, the building is supported on 18-inch diameter auger cast piles designed for an allowable capacity of 150 tons. We observed the full-scale load testing of the auger cast elements, analyzed the results, and confirmed our design recommendations.

*SEDC is an affiliate of Schnabel Engineering, Inc.
Photo: © Kevin Weber