Erection of precast-concrete girders for the aerial guideway of the $2.8-billion Silver Line rail project in northern Virginia has resumed, even as an investigation continues into the cause of longitudinal cracks found in several 96-in.-high units this past summer. Following a Metropolitan Washington Airports Authority design review, the project’s contractor, Capital Rail Constructors, a joint venture of Clark Construction Group LLC and Kiewit Infrastructure South, agreed to a design change to 84-in.- and 72-in.-high units specified for the guideway, allowing work to proceed on another section of the route across Washington Dulles International Airport. The girders were designed by Parsons Transportation Group, CRC’s lead designer, and fabricated by Coastal Precast Systems, Chesapeake, Va. MWAA hopes to make a decision on the more than 100 92-in. units, eight of which already had been installed when the cracks were discovered. The second phase of the $5.76-billion transit line is 13 months behind schedule, now set for completion in 2019.