The historic nature of the structure and corresponding lack of as-builts, its busy location and proximity to neighboring buildings, and numerous other issues combined to create no shortage of challenges for the design and construction team.
For starters, the building’s location at 18th and I Streets in the heart of downtown D.C., across the street from a busy Metro station, brought logistical challenges. There was only half a sidewalk for laydown space, and extensive foot traffic along with White House security restrictions added to the complexity.
The lack of as-builts also proved challenging. The new footings and foundation beneath the existing building were designed with little to no information on existing conditions. During construction, the team encountered some existing obstructions as they approached the bottom of the underpinning pits 15 feet below ground. After removing existing windows and some of the initial demolition work, they also discovered an issue with the existing building’s façade that required engaging a structural façade consultant late in the process to avoid project delays.
Protecting and monitoring neighboring buildings was another imperative. The ASU Barrett and O’Connor Center building shares walls with its two neighbors – one with numerous tenants including top secret agencies, doctors and others, and another that housed numerous pieces of valuable artwork that needed to be preserved.
DPR employed an array of high-tech strategies to address various challenges, including comprehensive clash detection modeling of the building utilities and structures, laser scans of the exterior shell, a robust monitoring program to ensure no movement occurred in the braced façade and monitoring the adjacent Metro tunnel during underpinning work. They developed a 4D phasing and logistics model to align construction with the milestone schedule.
The owner, DPR and adjacent property owners worked in close collaboration to determine requirements for monitoring the buildings to protect all entities during construction. Solutions included installation of a vibration monitor and other measures that ensured DPR was a good neighbor and adjacent building impacts were minimized.
To avoid delays after they discovered the structural façade issue, DPR worked collaboratively with the designer and owner to help procure a structural façade consultant. And to address various logistical issues due to the building’s busy, high-profile location, DPR closely coordinated street closures, site logistics and just-in-time deliveries. They restricted deliveries and movement in and out of the building to maintain public safety, among numerous other measures.