Work Speeds Ahead on Replacing Century-Old Bridges With Tunnel

Italian Gantries Headline North Carolina’s Biggest Current Project

Tue July 03, 2007 - Southeast Edition
Jodi Helmer



It is taking an international effort to construct a highway bypass in North Carolina.

Flatiron Constructors, a Colorado-based contractor specializing in complex transportation projects, is managing the 6.8 mi. (10.8 km) project to construct a bypass on U.S. Highway 17 around Washington, N.C., and Chocowinity, N.C., got underway in December.

Specialized equipment is being imported from Canada and Italy to complete the $192 million project — the most expensive N.C. Department of Transportation undertaking at this time.

Construction includes a four-lane bypass that stretches between Price Road and Hamilton Beach Road as well as a 2.9 mi. (4.6 km) bridge over the Tar River. The aim of the project is to divert traffic around the town of Washington, N.C.

Flatiron Constructors bid on the project in 2006 and came in as the lowest bidder with the highest score, explains Paul Newman, the project manager for Flatiron Constructors. The project involves several different contractors: United Contractors is the co-contractor on the project, Earth Tech is engineer of record and S.T. Wooten Corporation is responsible for all road construction, storm drainage and curb work and water and sewer construction.

S.T. Wooten Corporation began road construction in April. Over the past few months, 75 employees have been working 11 hour shifts to complete the first portion of the project which involved relocating the secondary roads.

Four Caterpillar D6 bulldozers have been preparing the site and material has been transferred with two 345 Caterpillar backhoes into a quad truck that holds 12 cu. yds. (9 cu m) of material.

The material was moved to a commercial bar pit and will be reused at the site of the new road.

The site is being prepared with four Ingersoll Rand 100 rollers and three Ramax walk behind rollers, as well as three Caterpillar off-road water tankers and two Caterpillar on-road tankers.

Three Caterpillar 322B backhoes are being used to prepare the site for drainage, water and sewer.

The road will be paved with asphalt with an aggregate base course (ABC). According to Greg Nelson, vice president of the heavy highway group for S.T. Wooten Corporation, it is much cheaper to use ABC under asphalt.

The biggest part of the Washington Bypass project is construction of the bridge.

Flatiron Constructors has contracted Deal, an Italian equipment manufacturer, to build launching gantries to construct the bridge.

“Deal is one of two companies in the world that builds this type of equipment,” Newman said. “We are a worldwide contractor and we believe in taking advantage of resources from all over the world.”

There was a conceptual design for the equipment in place at bid time. The entire design and construction process has taken more than 10 months and Flatiron Constructors made several trips to Europe to collaborate on the design.

The gantries, which have been nicknamed LG1 and LG2, were assembled onsite by Flatiron Constructors employees. Newman estimates it will take a crew of eight between four and six weeks to assemble the gantries.

The gantries are self-contained pieces that stretch 600 ft. (183 m) from tip to tip that will be used to drive the pre-cast piles, build bent caps, erect 120-ft. (37 m) pre-cast girders and pour the concrete deck.

Flatiron Constructors chose gantries for the job to save time: Instead of using one piece of equipment to build the entire bridge, gantries will be placed at each end of the bridge and construction will proceed toward the middle. According to Newman, using the gantries will cut construction time in half.

The bridge will be built one span at a time and all the construction will be completed without using interim access trestles. The variation of the top-down construction technique saves time and limits the disturbance to the local wetlands.

Unlike conventional construction plans when work on the ground must be completed before aerial work can commence, the top-down method allows above ground work to start at the same time that underground work is being done which results in much shorter construction schedules.

Manitowoc 777 cranes will be used on either side of the bridge to erect the segments.

Bermingham Foundation Solutions in Ontario, Canada, was hired to built specialized pile-driving equipment that will act as the framework to hold LG1 and LG2.

Newman expects that driving the piles will be one of the biggest challenges of the project. A lot of attention has been given to how use the new equipment to keep the piles in the right place, with the proper alignment and within tolerance once bridge construction starts later this summer.

The project is scheduled to be complete in November 2010.

“From an economic standpoint, because of the length of the project, it makes more sense to have specialized equipment built rather than renting equipment for such a long period of time,” Newman said. “It is also the best equipment for the job which is the most important thing.” CEG