New England already has at least one diverging diamond interchange; one such project opened to traffic in Providence, Rhode Island last year. However, the interchange project about to begin at I-89 Exit 16 in Colchester will be the first one of its kind in northern New England.

Colchester resident Jeanette Berry says it remains to be seen if the diverging diamond interchange will work. However, she sees no reason why it can’t.

“In the short term, I’m going to have to think about when I travel through the Exit 16 intersection and I can modify my travel patterns, potentially,” Berry said. “In the long term, I hope it will improve that intersection and improve the traffic flow.”

The project is expected to start by late January with construction of retaining walls. Unlike moving of utility lines, contractors can perform that aspect of the work at almost any time of year.

“It made sense for them to start with the retaining walls,” VTrans project manager Mike LaCroix said. “And we were OK with that, too, because the sooner we can get the retaining walls built, the sooner we can get the path open for pedestrians.”

At a Thursday night informational meeting, Berry learned a few things about the traffic lights in the project area.

“They’re going to be all coordinated,” she said. “But they also are going to have backup generators powered by natural gas, so that if there’s a power outage — theoretically — the lights will still function.”

Most of the work for the project will be done between 7:00 each night and 6:00 each morning. Any daytime work that will be necessary will be restricted to one lane only.

The two construction phases should be complete by the summer of 2026, possibly earlier.
Federal funds will cover the entire cost, which was substantially higher than VTrans expected.

“For the first contract, we’re looking at about $7 million to $8 million,” LaCroix said. “Then, the second contract will be in the $10 to $12 million ballpark, so you’re probably looking at the high teens, low twenties. The estimated cost of the project increased for a number of reasons, one of which was the current economy and trying to get contractors. It’s tough pickings right now, so unfortunately, we have to pay some sort of inflated cost.”

Vermont transportation officials have said for years that with about 25,000 vehicles per day, the Exit 16 interchange in Colchester has too much traffic for its current design to safely handle.