Unforeseen soil conditions surrounding foundations on a new $1.2- billion cable-stayed bridge have added as much as 18 months to the construction schedule, say officials at the Port of Long Beach, Calif.
"The soil has turned out to be more complicated than the engineers originally thought," says John Pope, port spokesman. The 1.2-mile-long Gerald Desmond Bridge is being constructed above two aquifers contaminated with benzene and subsiding land in an area marked by oil wells, he says.
The design-build team of SFI Joint Venture and lead designer Arup have conducted soil tests since 2012 that reveal varying geological conditions, so each bridge foundation requires its own separate design, says Pope. The job calls for about 300 piles to be drilled to depths between 110 ft and 180 ft.
Al Moro, chief harbor engineer, says that, besides liquefiable soils and a high water table, the project also sits in a seismic zone. Lateral movement is a design consideration for the bridge's piles and two 520-ft-tall concrete-reinforced main towers, he says.
"There is a limited amount of empirical data available about towers this size in this type of soil, so we got a lot of dynamic modeling going on, with different levels of seismic events to see how the tower design reacts," says Moro.
Moro, also the port's acting executive director, says that, because of soil conditions, SFI's submittals are taking "significantly longer than anticipated" to be approved by the port and Caltrans, which is acting as a third-party reviewer and will take control of the completed bridge.
The delay comes as the bridge design is about 70% complete. While the project team continues to submit new designs, construction is underway on approved sections on both the east and west sides of the bridge.
The late 2016 completion date for the project, which broke ground in early 2013, has been pushed back 12 to 18 months. The port won't know how much costs will rise or how many late fees will be assessed until, later this month, SFI returns to the Board of Harbor Commissioners with more estimates, Pope says.
The bridge has been designated as a National Highway System Intermodal Connector Route and is part of the Federal Strategic Highway Network. Nearly 15% of the nation's waterborne cargo is trucked across the bridge, according to port statistics.
The new Gerald Desmond Bridge replaces a 50-year-old structure that is no longer suitable for modern vehicle and shipping traffic volumes. The first cable-stayed vehicular bridge in California, it will connect the port to the city's downtown and feature three traffic lanes in each direction and a bicycle-and-pedestrian path. A 205-ft vertical clearance will accommodate today's large cargo ships.
SFI is a joint venture of Oakland, Calif.-based Shimmick Construction Inc., Spain-based FCC Construction and Italy-based Impregilo S.p.A. Parsons Brinckerhoff is the project manager.