MaineDOT photo.
Construction of the new Gut Bridge in the heart of scenic and picturesque South Bristol, Maine, should be substantially completed in the spring.
Construction of the new Gut Bridge in the heart of scenic and picturesque South Bristol, Maine, a coastal fishing town specializing in lobstering, should be substantially completed in the spring, with the Maine Department of Transportation (MaineDOT) project expected to be open to traffic in late May 2016.
The bridge spans the Gut, described as a tiny channel, which separates Route 129 from Rutherford Island. Although small, the channel provides a shortcut for boats that would otherwise have to circumnavigate the island.
Work on the bridge began in September 2014, and it should be completed in late November 2016.
Cianbro Corporation was awarded the contract on June 30, 2014 with its bid of $10.99 million to replace the swing bridge that was built in 1933. The project includes the bridge replacement and construction of an operator's house, new traffic warning systems, and some approach work.
In mid-September Cianbro completed the work that saw the installation of a temporary fixed bridge (single lane) and the implementation of the channel closure which began on Oct. 21.
“During the 213 days allowed for the channel closure,” stated the MaineDOT Web page for the project, “we will open the temporary bridge to traffic, demolish the existing bridge, construct the new bridge and remove the temporary bridge”.
The bridge replacement had been the subject of discussion by the town's residents for many years, with the Boothbay Register pointing out in a July 28, 2014, article that “the current swing bridge has undergone multiple mechanical failures and the process of replacement has been underway for almost a decade. The town originally recommended a large counterweighted bascule bridge, which was countered by a bridge proposed by South Bristol resident Beth Fisher. Boston based architect engineer Miguel Rosales designed this smaller hydraulic powered bridge that Fisher saw as more aesthetically pleasing than the original proposal.”
Hardesty & Hanover LLC (H&H) was brought into the project in early 2013 to develop a third alternative that closely matched the scale of the Rosales concept but provided operational reliability afforded by a counterweight balanced design. In the end, “this smaller bascule bridge” was approved.
“The hope is that the new bridge, developed as a sort of compromise,” stated the article, “will be more aesthetically pleasing than the first design that was presented. Some viewed the original bridge design as unnecessarily large.”
The design for the new bridge makes it easier for authorities to maintain and results in lower maintenance costs. Features include “self-lubricated sealed bearings, as well as materials that meet the standards for heavy-duty marine and industrial usage,” noted the article, which added that the current bridge experienced several mechanical failures in the summer of 2014.
Having a long-term reliable bridge in place is important for MaineDOT.
“A key concern with local residents is that the bridge fit in with the area,” said Michael Wight, MaineDOT's project manager. “The expected lifespan of the new bridge and its infrastructure is 75 years. This type of bridge could be used in other locations with similar span length. An extensive public process and public outreach was undertaken and MaineDOT is working closely with local town officials to give them a new bridge and ensure the success of the summer tourist season.”
Peter Roody, Hardesty & Hanover's chief engineer of bridges and movable structures, started working on the design of the new bridge in February 2013.
“Key design challenges included a highly congested work site, bedrock with no overburden, heavy year round navigation and traffic maintained throughout construction,” he said. “Design innovations included abutments founded on bedrock, constructed without traditional cofferdams; and a cable-stayed bascule bridge superstructure and a lightweight orthotropic steel deck. Counterweights are located in the tower masts and below grade to minimize the scale of the structure. This was a key design requirement established during meetings with the community. Their input and ideas were invaluable to the design process.
“The design carefully considered reliability and maintainability of the new structure,” he added. “Critical bearings are located above the flood plain to ensure reliability. The girders are sealed box elements that are protected by a thermally applied paint system called metallizing. This system provides the most durable protection for a steel bridge. The existing bridge opens more than 8,000 times per year and more openings are expected with a mechanically reliable structure. Gear driven machinery was selected as the most reliable system to open the bridge.”
When Cianbro crews arrived on site the first goals of construction were to build new retaining walls/abutments adjacent to the bridge, which reduced traffic flow to one lane. Following the winter break, Phase I work resumed until June 15 so that it would not impact the summer tourist season.
Phase II work started on Sept. 14 and with the closure of the channel, traffic was rerouted onto a temporary bridge placed east of the current one. The goal is to have the new bridge open to traffic in May, while work continues on the approaches and minor elements.
“During the 213 day channel closure,” noted the project Web page, “Cianbro will have two 8-hour shifts working each day Monday through Friday. Each shift will be working around low tide. Cianbro does not plan to work weekends, however, weekend work may be needed depending upon weather and other factors. After that time, work will continue, including constructing the approaches, dirt work, paving, etc. The contract completion date is Nov. 15, 2016, though MaineDOT is optimistic that it will be completed during the summer months.”
Although this project is smaller compared to some of the bigger projects taking place in Maine, it is still a challenging one.
“Discussions with town officials, Cianbro, the U.S. Coast Guard and local fishermen were all part of the process to develop a construction schedule for the project,” said Wight. The in-water work window restrictions based on input from multiple environmental agencies are key to the construction schedule. Movable bridges in such tight settings are very rare. Cianbro did a significant amount of planning to prepare for working in such a tight site. Closing the bridge down to boat/vehicular traffic, along with using a temporary bridge, was key to providing space for the contractor to work. The crane being used on the project had to be partially assembled off site due to the lack of space.
“Good weather and having no surprises will help keep the project on schedule,” he added. “Good planning also is very important. Open communication and getting quick decisions is essential during this phase of the project to get the bridge open on time. Having to work the tides makes for some long days for the contractor's crew. There have been no major surprises yet. Partnering is being used on this project. With partnering, we make decisions as quickly as possible with the team working on the site.”
The new bridge will require 934 cu. yds. (714 cu m) of concrete, 106 tons (96 t) of steel and 287 tons (260 t) of asphalt.
In addition to Maverick, other subcontractors include Maine Drilling and Blasting for the rock anchors, and Plummer Excavation is providing fill. At peak construction Cianbro will have about 20 workers on site.
Wright noted that the traffic management plan is working, with an emphasis on ensuring that the construction workers can work safely.
“The traffic is flowing well for the most part,” he said. “A very small number of vehicles are running the red light and speeding. MaineDOT encourages all drivers to obey the speed limit and obey all traffic signs and signals.”
“This is a definitive team project and is providing opportunities for our newer employees to gain experience on smaller rural projects,” he said. “Mentoring is very important at MaineDOT and is vital to help new employees develop. Public involvement is critical on projects of this type. It also is very important for MaineDOT to work closely with contractors on projects with very tight schedules.”
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