ICC officials said the overpasses are safe for motorists to continue using but will need to be reinforced or rebuilt to last for the 50 to 100 years of a typical bridge’s life span.
“This has absolutely nothing to do with the safety of people traveling over the bridges,” said ICC project spokesman Ray Feldmann. “These bridges have functioned absolutely fine since they opened. This is really about the long-term durability of the bridge structures.”
Some lanes of the ICC will probably be closed over the next two weeks as workers reinforce the pier structures with tensioned steel wire until a long-term solution can be found, ICC officials said. All three bridges will remain open, they said.
Feldmann said inspectors found 40 to 50 concrete cracks total in all of the three overpasses’ combined 13 “pier caps.” Those concrete caps sit atop the supporting piers and connect them to the overpasses’ steel understructure. The cracks are .005 to .035 inches wide and range from seven inches to 3 feet 8 inches long, Feldmann said.
Melinda Peters, the state’s director of the ICC construction project, said that the cracks stem from a design flaw and that Intercounty Constructors, the joint venture of construction firms that built the project, will pay to fix them. The design firm used an inaccurate model to determine how many steel rods were needed inside the concrete pier caps to properly fortify them, she said.
The State Highway Administration reviewed the engineering calculations that the designs were based on, she said, but not the actual computer model that designers used. The design firm’s model made inaccurate assumptions about how the pier caps would attach to the bridges, she said.
“We don’t get into every detail of the models they use as part of our review,” Peters said.
Project officials are still reviewing overpasses that have been built on the rest of the 18.8-mile ICC, which is still scheduled to open east to Laurel by the end of the year. However, Peters said, the remaining piers were designed by another firm, and no problems have been found so far.
Peters said workers will wrap steel cable around the pier caps to prevent the cracks from growing until a long-term fix is found. If the caps need to be rebuilt, she said, most of that can be done while traffic runs on the overpasses, something routinely done when older bridges are repaired.
The ICC has been criticized for its relatively steep construction costs, funded in part by bonds that will be paid off via some of the highest toll rates in the country.
Montgomery council member Phil Andrews (D-Gaithersburg-Rockville), a longtime ICC opponent, said he’d still like to know how such a design mistake was allowed to occur. He said some of his constituents who use the Needwood Road overpass daily “might wonder if that assurance [that the overpasses are safe] is 100 percent reliable given that these problems happened in the first place.”
Design on the overpasses with cracks was done under a joint venture of Parsons Transportation Group and Jacobs Engineering, ICC Officials said. The construction on the first segment has been done by Intercounty Constructors, a joint venture of Granite Construction Co., Corman Construction and G.A. & F.C. Wagman Inc., ICC officials said.
A spokeswoman for Parsons Transportation Group referred questions to state officials.