How MaineDOT Replaced an Interstate Bridge In 60 Hours

By Devan Eaton, PE, and Ben Walz, PE

As departments of transportation look to replace aging bridges in high-traffic areas, the use of accelerated bridge construction (ABC) is increasingly among the delivery options they consider. In addition to its growing track record of successful weekend completions, ABC has been shown to increase work zone safety and minimize delays for the traveling public. That was the case for Maine’s Veranda Street Bridge Replacement Project. 

The Veranda Street Bridge carries Interstate 295 over the two-lane divided Veranda Street in Portland, Maine. In 2017, an inspection found the 61-year-old bridge to be in satisfactory-to-poor condition and structurally deficient. As MaineDOT began the process of replacement, we sought a demolition and construction method that would minimize inconvenience to the approximately 54,000 motorists who use the bridge daily and the more than 15,000 motorists who travel Veranda Street daily. Our decision to demolish the existing bridge and deliver the new structure by accelerated bridge construction resulted in one of the largest, fastest ABC projects MaineDOT has undertaken. We began deconstruction on Friday, April 22, at 6:45 p.m., and 60 hours later, on Monday, April 25, at 6:52 a.m., the new bridge was in place, paved, striped, and opened to traffic. 

Cost-benefit analysis 

A cost-benefit analysis revealed accelerating construction of the $21.7 million project would:

• Cut construction time by 50 percent, saving the public years of congestion and inconvenience
• Reduce traffic impacts and travel delays by 80 percent 
• Improve the safety of workers and the public

Further, we learned ABC would eliminate the need to construct a substantial and costly temporary bridge. The money we saved and the benefits we received by not constructing a temporary bridge helped to offset the cost of using ABC.

Selecting partners with experience

A proven strategy for mitigating risk is to contract with partners that have significant experience and a history of delivering success for our department. 

Plans called for replacing the existing three-span bridge with a low-maintenance, jointless, single-span structure, featuring wide shoulders for improved visibility and safety on I-295. Because the new bridge would be shorter, we planned to convert the remaining area underneath the existing structure into embankments prior to the roadway closure. To avoid post-construction settlement-related issues associated with the marine clay present at the project site, the new embankments were constructed using over 9,000 cubic yards of geofoam lightweight fill. Construction of a majority of the new embankments beneath the existing bridge in advance of the closure was critical to limiting the roadway closure to a single weekend. 

“We knew the closure duration needed to be minimized to the absolute greatest extent possible. Achieving that meant devising a solution that allowed the existing bridge foundations to remain in place while also maximizing the amount of embankment built prior to the road closure,” said Tim Cote, project manager for HNTB who provided structural and geotechnical, as well as highway and traffic engineering services for the bridge replacement. “At the same time, post-construction settlement needed to be within acceptable limits. It was a complex set of challenges, but the proposed lightweight fill design was critical to the successful outcome of the project.”

To minimize disruption of traffic on I-295 and Veranda Street, the upper portion of the new northbound and southbound bridges were built on temporary abutments next to the existing bridge. At the same time, the new bridge abutments were built beneath the existing bridge. This approach allowed traffic to proceed on each roadway with minimal interruption. Once the preparatory work was complete, I-295 and Veranda Street were closed, crews lifted the new northbound and southbound bridges off their temporary supports, and “drove” each section into place using Self-Propelled Modular Transporters. The SPMTs’ built-in jacks then raised the decks 24 feet to a new, higher bridge clearance of 15 feet 6 inches. 

“We were able to bring the construction of the bridge decks down in elevation to 8 feet above the ground with the incorporation of Mammoet’s MJS 300 Cradle System, integrated with SPMTs,” said Tom Senior, project superintendent for Cianbro. “This was the first time this system was used to move this type of structure. It afforded us the flexibility to raise both structures to final elevation and lower them into final position.”

A need for closure

Because safety is of the utmost importance to MaineDOT, we chose to fully close I-295 and Veranda Street while the existing bridge was demolished and the new structures were rolled into place. It created a much safer environment for everyone and allowed the work to be completed as quickly as practical. 

“We recognized the challenges and risks to the traveling public in performing construction over an active roadway, which is why the decision was made to choose the alternative option of building the superstructure completely off-line and away from traffic. Using SPMTs allowed us to build the superstructure bridge decks, bridge abutments and lightweight approaches away from traffic,” said Brian Hartness, who served as Cianbro’s second superintendent during the weekend bridge move. 

A significant public information and outreach campaign was implemented to advise the public of the planned closure, strongly encouraging motorists to avoid the area during the interstate closure, and to share the benefits of accelerated bridge construction. These factors were critical to successfully managing traffic and informing the public of the benefits of the project approach. 

We had many in-person meetings and workshops with the public and project stakeholders before the pandemic. During the pandemic, when the project went out to bid and then into construction, we relied on virtual public involvement to maintain our policy of transparency and open communication. We found it to be more effective, efficient, and far-reaching than traditional communication channels. 

Leading up to this project, our virtual public involvement process consisted of pre-recorded presentations played on-demand with public comments collected and responded to as they were received. For this project, we implemented MaineDOT’s first virtual podium meeting. Through this process, we provided a live presentation online. Offering the meeting online gave constituents the opportunity to attend and participate from wherever they were. Following the live presentation, the meeting attendees were invited to type questions or comments in a chat box; those questions were then answered in real-time by project team members. The benefits were significant:

• We engaged a larger, broader audience.
• We were able to correct misconceptions instantly, as would be done at an in-person meeting.
• We made the recorded meeting available on-demand for those who could not attend the live meeting.

The success we experienced with virtual public involvement on the Veranda Street Bridge Replacement Project reaffirms MaineDOT’s intentions to move forward with virtual public engagement as a standard practice in the future.

Earning the public’s trust

Implementing accelerated bridge construction for the Veranda Street Bridge Replacement Project resulted in a new, lower maintenance bridge delivered in record time and with broad public support. The successful delivery of this project allowed MaineDOT to build public trust and further position our DOT as a progressive, innovative agency constituents can count on when every day counts.

Devan Eaton, PE, is project manager for the Maine Department of Transportation.
Ben Walz, PE, is resident engineer for the Maine Department of Transportation.