Tobacco Trail bridge construction in home stretch
Builders say the American Tobacco Trail’s new bridge over Interstate 40 will be ready for the opening ceremony the city has scheduled for Oct. 12.
A key milestone passed last week when workers finished pouring the bridge’s concrete deck. Another comes this week when a subcontractor arrives to pull and “tension” the 12 internal cables that will give the span much of its strength.
“There are a lot of moving parts on this job,” said Eric Norton, project manager for Blythe Construction, the contractor the city hired to erect the 268-foot crossing.
The $7.5 million project is completing the Durham portion of the tobacco trail, tying in with existing sections north of N.C. 54 and south to the Chatham County line.
About 80 percent of the cost is going toward the bridge itself, with the rest going toward the installation and paving of several trail sections.
The trail itself is all but complete, save for a couple of stretches adjacent to the bridge that’s doing double duty at the moment as an access road for Blythe and its subcontractors.
Residents are already using the trail sections Blythe placed south of Renaissance Parkway.
The bridge proper has been by far the most challenging in addition to being the most expensive part of the project. City officials for appearance reasons opted for an arch-type design that helped make the new span one of the few of its type in the country.
“Everything here is hand-crafted,” Norton told members of the Durham Engineers Club who toured the site last Wednesday. “There were a lot of challenges. It’s the reason nobody [else] bid this job.”
Norton was alluding to the fact that Blythe was the only contractor that responded early in 2012 to the city’s request for bids.
The twin arches that soar over the interstate proved the project’s biggest headache, as federal regulations forced the city, design firm Parsons Brinckerhoff and Blythe to find a made-in-America source for the steel that went into them.
That wasn’t as simple as it sounds. “They don’t make 30-inch [diameter] inch-and-a half wall pipe in the U.S. anymore,” said Tim Hayes, supervising engineer for Parsons.
Eventually, builders turned to a Houston firm that crafted the arches out of plate steel. It took 10- and 20-foot-long plates, rolled them, pieced them together and sent them to another company to bend into shape. It wound up delivering four pieces, two for each arch. Workers for Blythe finished the assembly on site.
That took 48 consecutive hours of welding and inspections, a job finished mere hours before crane crews lifted the arches into place over I-40, said Hayes and Clif Aldrich, Blythe’s bridge superintendent.
“It was all hand-welded,” as automated welding machines were out thanks to some of the detailing on the finished steel, Aldrich said. “Two guys, just steady burning. And we barely made it. We made it four hours before we had to shut the road.”
The lift of the arches occurred early April 28, and was also proceded by some corrective work to the piers supporting them on one side of the road. Thanks to a survey error, they were intially a couple of feet too tall, but it proved easy to pare them down to the right size, Hayes said.
The piers themselves were drilled 50 feet into the ground, the last 20 feet into solid rock, Aldrich said.
Weather and a couple of metals thefts have provided additional challenges.
The rain by itself has cost Blythe 72 days of work, Norton said.
The theft of about $28,000 work of aluminum parts also helped put the project behind, as they’d been custom-crafted and had to be replaced for work to continue, Aldrich said.
Aldrich had the satisfaction of catching a couple of other would-be thieves red-handed in August as they were taking some steel from the project site.
“I guess they didn’t expect us to be out here working at 8:30 in the morning” on a Saturday, he quipped, adding he summoned police who wound up charging the men involved.