HAVERHILL — A $102 million construction project to replace one of the Interstate 495 bridges that crosses the Merrimack River is slated to start next week, and won't be completed until June 2022.
The project spans the length of the highway, both north and south, between exits 48 and 49, including the 712-foot bridge. The project, which will completely demolish and replace the existing bridge, is expected to take place in four stages over the next four years.
During a public meeting on the project held at City Hall Wednesday evening, representatives from the Massachusetts Department of Transportation and the general contractor for the project, SPS, said that despite the scope of the project, three lanes of travel will be maintained in each direction throughout its entirety.
"Three lanes will always be maintained on 495 in every phase, with the exception of temporary nighttime closures during off-peak times," said Matthew McCue, project executive for SPS. "There is obviously an incredible amount of work to be done, so we do anticipate working 24 hours a day, seven days a week at times."
The project, which is funded by the federal government (80 percent) and the state (20 percent) will be the largest current project in the North Shore's highway district, said Mass DOT spokesman Dan Fielding. It is tens of millions of dollars more expensive than the Methuen rotary replacement, which was just completed this year.
The existing bridge, which is 57 years old, is in "dire" need of replacement, McCue said. Murthy Kolla, the Mass DOT project manager, said the state agency spent "a whole season going through, doing additional repairs" to both the bridge's deck and underside, just to extend its life through the length of the replacement project.
The new bridge will be wider, with full-width breakdown lanes on each side of both travel directions and a new exit-only lane on the northbound side for Exit 49.
Bridge replacement will take place in four phases. The first phase, scheduled to begin the week after Labor Day, will not impact the existing travel lanes. A new northbound bridge will be constructed in the median of the existing northbound and southbound lanes.
In the second phase, beginning September 2019, northbound traffic will travel on the new bridge while the old northbound bridge is demolished. The additional breakdown and exit-only lanes will be added to the new bridge.
Phase three, set to begin in August 2020, will see the new bridge carrying both northbound and southbound traffic between its six lanes — three travel lanes, two breakdown lanes, and the exit-only lane, which will act as a travel lane during this period. The southbound bridge will be demolished and rebuilt.
Phase four, from September 2021 to June 2022, will focus on median restoration.
The Mass DOT and SPS representatives at the meeting said the project is lengthy because state environmental regulations only allow them to access the river from Nov. 16 to Feb. 28, necessitating ice-breaking moors upriver and potentially ice-breaking tugboats. This is to protect the sturgeon, a type of fish, that live in the river.
"It's a nasty looking fish," McCue joked, "but apparently they have been located in the river, so we do have those restrictions."
To mitigate the impact on commuters and Haverhill residents, Mass DOT will place 12 electronic message boards on I-495 and connecting roadways that will display real-time updates on travel conditions, including travel times. Lanes will only be closed during "off-peak hours," which vary based on the roadway location and traffic volume, but are generally between 8 p.m. and 5 a.m.
The speed limit will be reduced from 65 mph to 55 mph during construction.
The crews will also implement a "noise monitoring program."
"There will be noise associated with it," McCue said. "We feel that the phasing will allow us to do a lot of the demolition during the day."
No traffic will be detoured through the city during construction, because all travel lanes will remain open during peak traffic hours, McCue said.
"The goal is to keep traffic on the highway. We never want to detour them through city streets or anything like that," he added.
Frank Welch, the project's resident engineer from Mass DOT, added that the agency "formulated a schedule, knowing what causes a backup in traffic, in an attempt to minimize backups."
The new bridge, once completed, will have only two support beams per side, instead of the existing four, and will have no joints across the deck, enabled by stronger steel. Those changes should help prolong the life of the structure, said John Smith, design manager for HNTB, the firm that designed the project.
The lifespan of the new bridge will be 75 years.
More information and updates on the project can be found at mass.gov/i495haverhillbridge.