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A unique bridge for a unique vista

Agency of Transportation, contractors introduce public to new Interstate 91 bridge

BRATTLEBORO—The view from Route 30 of the Interstate 91 bridges that span the West River between Exits 2 and 3 is scheduled for an up-cycle.

The two 50-year old towering steel-and-rivet bridges that traverse the West River will be demolished over the next few years and replaced with one concrete bridge that the Vermont Agency of Transportation (AOT) touts as a pilot project on a fast timeline.

The AOT and design-build firms FIGG Engineering Group, of Florida, and PCL Civil Constructors, Inc., of Virginia, unveiled the designs for two new bridges on Interstate-91 July 23 at a well-attended public meeting in the Brattleboro Union High School multi-purpose room.

The project will also replace a smaller bridge over Upper Dummerston Road.

Demolition and construction begins October. The design-construction team anticipates completing the project in 2016.

Most large bridges take five years to replace. Planners say the Interstate 91 bridge is scheduled to take three years.

FIGG and PCL have dubbed the new, larger bridge as a “gateway to nature.”

The existing steel bridge has flaws in its design, said Matt Mann of the Windham Regional Commission (WRC). He explained that the bridge is held together by thousands of nuts and bolts, and can weaken.

“If even one gets loose and breaks, then a section of the bridge can be compromised,” said Mann.

As the bridge aged, AOT had the choice of replacing all the nuts and bolts or replacing the bridge, he said.

According to Mann, the West River bridge will serve as a pilot project for the state. It is one of the state’s first design-build projects — the first being the Interstate 91 bridge over the Williams River in Rockingham — and also received a relatively high level of public input into the structure’s aesthetics.

The AOT normally weights transportation projects at 60 to 70 percent on cost, with lower ranks for technical feasibility and aesthetics, said Mann.

This pilot project’s rating has cost weighted at 50 percent, technical aspects at 30 percent, and aesthetics bumping up more than usual to 20 percent, said Mann.

According to Mann, AOT unveiled the bridge’s original design in a public meeting last year. The audience turned green at the sight of the proposed design.

The WRC responded and asked the AOT to reconsider the bridge’s aesthetics and allow for more public input, said Mann. It agreed, and, given the required timelines of publicly funded projects, the WRC and AOT scrambled to gather public input, he said.

Along with the input from the public meeting, the WRC assembled an aesthetics committee composed of the WRC commissioners, representatives of the town of Brattleboro and Dummerston, and Kate Anderson of the Brattleboro Town Arts Committee.

The aesthetics committee assembled a number of criteria for the final design which AOT included in its request for proposals.

The bridge project is also unique due to the number of surrounding roads and trails. The construction team must co-ordinate with travel on Route 30 and Upper Dummerston Road, as well as the West River Trail, the West River Park, and the West River itself.

Linda Figg, president and CEO of FIGG Engineering Group, said the Vermont landscape inspired the West River bridge’s design.

“It’s all about the landscape,” she said, adding that FIGG wanted to “create a bridge that helped reflect nature.”

According to FIGG’s website, the company aims to construct bridges that double as works of art. The company has gone as far as staining a bridge in Moab, Utah, the color of the surrounding desert so the structure would blend into the scenery.

FIGG has built bridges across the country, including the Penobscot Narrows and Observation Bridge in Maine, and the Leonard P. Zakim Bunker Hill Bridge in Boston.

Figg said that the new concrete compression arch over the West River will last more than 100 years. The new design will have a wider span than its predecessor and will open the view. The four pillars supporting the bridge will have a textured concrete surface designed to relate to nearby stone outcroppings.

Along with the natural environment, Figg said designers also used the original state seal — which sports a white pine tree with 14 branches — as inspiration, and incorporated it into the observation platforms.

The Brattleboro Bridge Improvements Project calls for the demolition of four bridges — two spanning Upper Dummerston Road and two spanning the West River — and replacing them with two bridges.

According to information from FIGG and PCL, the new West River Bridge steel bridge will be replaced with a single 1,036-foot long, 104-foot-wide arching bridge on 70-foot tall piers standing on two public observation platforms.

The new concrete bridge will have two arching piers, and be textured and stained to mimic stone. Its hollow core will help lessen road noise. The bridge’s “under-dome,” viewed from Route 30 and the river, will be stained blue, to evoke the sky.

A steel and concrete safety rail will have openings that designers say will provide drivers with open views of the surrounding landscape.

Kayak and canoe launches will be sited near each observation platform.

The bridge over Upper Dummerston road will span 85 feet and offer a clearance of 15 feet 6 inches.

“We hope that you will love this bridge and [that] it be an exciting addition to your community,” said Figg.

Caleb Linn, engineer with PCL, said that Interstate 91 will be reduced to single-lane traffic for most of the demolition and construction.

The project is in its first phase as the construction team gathers its remaining permits and utilities near the bridge are relocated.

Next, the team will shift traffic between Exits 2 and 3 to the southbound interstate lane. Once that’s complete, the northbound bridge lanes will be demolished and construction on the new bridge will begin.

Linn said the concrete bridge will go up as a balanced cantilever, with sections of the bridge extending one by one in opposite directions from the support piers.

Once the first pier is constructed, the construction crew will cast one section of the bridge, then cross to the opposite side of the pier and cast the next section, he said.

Travelers on Interstate 91 will experience the greatest construction delays as the interstate will be one lane. Travelers on Route 30, Upper Dummerston, and the West River Trail will experience limited road closures.

Closures should last for a “matter of hours,” said Linn. “For the most part, hopefully, you won’t even notice us,” he said.

As far as the construction crew goes, “the goal is to hire craft locally,” said Linn. He estimated work would involve 50 workers on site.

According to AOT Chief Engineer Rich Tetreault, this $60 million project is the biggest bridge project the state has ever seen.

In an unusual move for a bridge project, especially one in the federal highway program, AOT put this project through a design-build process.

Normally, said Tetreault, state and federal construction projects follow a design-bid-build process in which AOT designs a new structure in house — in this case a bridge — then sends out the project for bid. The winning construction company then builds the new structure.

In a design-build, the AOT sent out a Request for Proposals (RFP) listing the project’s criteria and requirements. Design and construction companies teamed up and responded to the RFP with their own designs.

One advantage in this process, Tetreault said, is that the designers and engineers are at the table together at the outset, saving the state money. Another advantage, he said: Should issues with the design or project surface, they’ll likely do so prior to construction.

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Originally published in The Commons issue #214 (Wednesday, July 31, 2013).

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