U.S. 17 bridge over Tar one of nation’s top 10
Published 11:08 am Saturday, November 10, 2007
Construction begins near Chocowinity
By DAN PARSONS
While it may be causing inconvenience for Washington residents, the U.S. Highway 17 Bypass bridge project has gained national attention as one of the top-10 bridge projects in North America.
The future 2.9-mile bridge, the middle phase of the three-phase, $192 million Washington bypass project, landed at number eight on the list, compiled by Roads and Bridges Magazine.
Design firms, state transportation officials and engineers nominated nearly 60 bridge projects in North America. To be nominated, the projects were required to be in the design or construction phase within the past 18 months.
For the past three months, it has been the equipment to build the bridge, rather than the bridge itself, that has been under construction.
To move the concrete bridge components, two yard gantries, each able to lift 75 tons, have been built, one in each of the two materials yards on either side of the river.
The large yellow structures which can be seen from highway 17 east of Chocowinity and from U.S. Highway 264 west of Washington are the yard gantries. Beneath each are two 585-foot long trusses, parallel to the ground, which will lower each span of the bridge into place as construction progresses out over the river. Each crane had to be transported to the site in pieces and assembled in place, according to Paul Newman, project manager for Flatiron/United, the company contracted by N.C. DOT to build the bridge.
The gantries will lower each 120-foot span of the bridge into place. What makes them unique is their ability to drive piles to support the bridge as construction progresses. The gantry crane on the south side of the river is commissioned and working, according to Newman. At that end of the bridge, two spans have been lowered into place and piles are being driven for the third.
The company chose this sort of “top-down” construction to minimize the impacts to wetlands that the bridge will pass over on both sides of the Tar River. Retrofitted with pile drivers, a patent-pending innovation, the cranes eliminate the need for a temporary bridge alongside the permanent structure during assembly.
Newman said the concrete deck for the first span was poured Tuesday. The bridge will require 128 spans with each crane constructing about half, working toward the center from each end. The entire project is scheduled to be finished Aug. 31, 2010.
The gantry on the north side of the Tar River is nearly assembled, Newman said. He expects the crane to be commissioned and begin laying spans within the next week. A portion of the north end of the bridge, as it crosses Kennedy’s Creek, will split into two parallel spans, which may slow the progression of the bridge southward. The two halves of the bridge, however, will not meet over water, but on the south side of the river.
To ensure that both ends meet in the middle, the construction crews are using both land surveying and global positioning satellite technology to plan construction.