BANGOR, Maine — How do you replace a bridge in a weekend?

The key is preparation, according to Brian Marquis, senior technician for the Maine Department of Transportation.

After a 65-hour shutdown, the Interstate 395 bridge that stretches over Webster Avenue reopened the afternoon of May 9, a day ahead of schedule. Today, commuters are traveling over an entirely new bridge. The project cost $2.6 million.

Instead of replacing the heavily traveled bridge in sections, which likely would have affected traffic and closed lanes throughout the summer, MDOT decided to get it out of the way as soon as possible.

To get it done quickly, crews started working underneath the bridge in October, starting construction on an arch tunnel that would replace the existing bridge’s substructure. That work stalled for a brief time over the winter before picking up again in the spring.

At 8 p.m. on May 6, the road was shut down, and demolition crews started chipping away, using 16 excavators with various attachments, a pair of bulldozers and other heavy equipment.

The subcontractor hired to demolish the bridge, J.E. Butler LLC of Holden, asked Compusult Inc., a computer consultant, to put together a time-lapse video of the project, which condenses about 65 hours of work into a minute.

Bangor-based S.E. MacMillan Inc. was general contractor for MDOT on the project.

First, Butler crews broke up the old deck, cut up the existing girders and hauled the debris away. By May 7, crews were dumping and leveling gravel on top of the arch tunnel to serve as the base of the new road. On May 8, they paved it. On May 9, they moved off their equipment, closed the detours and reopened the bridge.

“The subcontractors did their work very efficiently,” Marquis said.

Maine DOT spokesman Ted Talbot said last week there was a bonus of $7,500 per hour with a maximum of $100,000 for finishing the project early.

Follow Nick McCrea on Twitter at @nmccrea213.