Workers began installing a series of arched carbon-fiber tubes as part of the new Herrick Road Bridge in Belfast Sept. 22.

The bridge is among the first in the world to use a new technology developed at the Advanced Structures and Composites Center at the University of Maine, Orono, called “bridge-in-a-backpack” — so named because the structural components are light enough to be moved without heavy machinery.

Daniel Bannon, a structural engineer with Advanced Infrastructure Technologies — the Orono-based company to which the University licensed the technology in 2009 — was on site Thursday, Sept. 23, while workers from Pittsfield-based Stetson & Watson installed the 16 tubes that will form the backbone of the Herrick Road Bridge.

Each of the tubes is 50 feet long, made of a thin carbon-fiber reinforced resin, and wide enough to easily roll a basketball through. At a glance, they resemble segments of sewer pipe.

Bannon said each of the tubes weighs around 200 pounds — a fraction of what a steel beam would weigh. On Thursday, a crane was lowering them into place, but Bannon said that had more to do with the steep banks leading to the work site than with the weight of the tubes.

Unlike steel beams, the composite tubes are light enough that they can be moved by hand. AIT has been working with several Caribbean Island nations, and Bannon said the technology is a natural fit for places where hand labor is plentiful and heavy machinery scarce.

In response to a question from a curious neighbor who had come by the work site, Bannon said the composite material is twice as strong as steel. These tubes, he said, were designed to hold a standard automobile bridge load as defined by the Maine Department of Transportation.

“They could be designed to be stronger, but there’s no need to,” he said. “It would be overkill.”

“They should make one you can walk up inside,” said the neighbor.

Later, Bannon acknowledged that the new technology had piqued the curiosity of lots of people, from a farmer in Nebraska who wanted to use the composites for a cattle barn, to a group working on the 2014 Winter Olympics Games in Sochi, Russia.

While mention of the Olympic Games suggests the material may eventually be highlighted in the architecture — AIT has also considered using longer tubes for suspension bridges, hanging the deck below the arches — for now, it is being used in a way that renders it nearly invisible once the bridge is complete.

After the tubes are installed, they are filled with a special concrete of water-like consistency, pumped into each arch through a three-inch-diameter hole at the top. The arches are then covered with a decking material. Walls are erected on the outer faces of the bridge, allowing the space between the arches and the roadway to be filled with gravel. In the finished bridge, the tubes are visible from underneath, Bannon said.

To date, Bannon said, the cost of bridges using the composite tubes has been consistent with MDOT estimates for conventional bridges.

“That’s very promising,” he said. “These are the first few of these bridges to be built. Being able to be competitive early on is exciting.”