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December 8, 2020

Century-old Gardiner bridge replaced using 21st-century accelerated construction

a concrete bridge over a rocky stream with brick two and three story buildings on the other side Courtesy / Stantec Gardiner's Bridge Street Bridge, which carries U.S. Route 201 over Cobbosseecontee Stream, is open to traffic after it was replaced, a process that used lateral slide technology, only closing the bridge to traffic for 30 days. The A-1 Diner, the small yellow building on the far side of the bridge, is connected to the bridge and was part of the replacement project.
Where are the two bridges that were replaced in Gardiner?
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A century-old bridge in Gardiner has been replaced using 21st-century technology that accelerates the construction process, the second bridge in the state to use the method.

But the Gardiner bridge replacement project won't be the last — accelerated bridge construction, also known as the unilateral slide bridge approach, will also be used on the Veranda Street Bridge replacement in Portland when it begins this month.

With the lateral slide process, the lower portion of the new bridge is built below the existing bridge while it's still in use. The upper portion is then built next to the new bridge on temporary supports. When the upper part is ready, the surface portion of the old bridge is torn down and the new one slides over onto the new supports to take its place.

The first bridge replacement to use the technology was Littlefields Bridge over the Little Androscoggin River in Auburn, in 2013.

The 700-ton new Bridge Street span that replaced the 103-year-old bridge was slid into place last week, and the new bridge has reopened to traffic after being closed for 30 days. Stantec's Portland office led the project design on the Maine Department of Transportation Bridge Street Bridge replacement, which completes a major part of the final phase of Gardiner's downtown comprehensive transportation improvement project.

The much smaller Maine Avenue Bridge in downtown Gardiner on Route 24 over Cobbosseecontee Stream was also quickly replaced, but not using lateral slide. Built in 1933, the smaller Maine Avenue Bridge was closed for 15 days.

Gardiner's unique downtown, which is on the Kennebec River waterfront and sliced by Cobbosseecontee Stream, made the quick bridge replacements necessary — both local and regional travelers have to go over one of the bridges to get through downtown.

"Planning and design of a bridge replacement in a bustling and distinctive downtown like Gardiner requires an extensive level of collaboration and preparation to ensure that modern mobility upgrades still complement a community's character and needs," said Tim Merritt, a principal with Stantec.

He said the Bridge Street replacement also had to accommodate the A-1 Diner, which is suspended over the water and connected to the east side of the bridge. The project also took into account minimizing disruption to nearby historic properties, as well as the endangered fish species in Cobbosseecontee that are the focus of active conservation efforts.

Stantec designed the two bridge replacements as well as a recreational trail bridge that connects to the Kennebec River Rail Trail. Trail enhancements include landscaping; using salvaged granite; ornamental lighting; interpretive panels celebrating the stream's historic dams, fish species and birds of prey; and safety features.

Reed & Reed Inc., of Woolwich, is the project general contractor, and McGee Construction, of West Gardiner, is subcontractor. Design subconsultants are Haley & Aldrich, of Portland, for geotechnical and TMSI for signalized intersections and utility coordination.

a m ap showing a  highway with a small part blocked out
Courtesy / Maine DOT
A Maine Department of Transportation map shows the project site of the Veranda Street Bridge replacment, which is scheduled to begin this month.

Veranda Street Bridge is next

Maine DOT's Veranda Street Bridge replacement will include replacing the span on Interstate 295 that crosses over Veranda Street at the north end of the city with a new single-span bridge. It also involves reconfiguring and reconstructing Veranda Street between Wordsworth Street and Martin's Point Health Care. That work will include a bike lane and sidewalk and improving drainage.

The bridge was built in 1961, and the divided spans, the interstate ramps "and the confusing nature of the roadway network" have made it an increasingly high-crash area, Maine DOT says in its project description.

Construction was originally scheduled to begin in the fall, but the state had to re-advertise for construction in September, spreading out the timeline. The project is now expected to be completed in 2022. It will be determined by February whether the bridge closes for a month in October 2021, or in April 2022, depending on the contractor, the DOT website says.

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