Until, that is, it became clear what the construction might actually entail: up to a decade of major disruptions for commuters and a temporary structure in the Charles to carry Soldiers Field Road.

It was a decisive call after five years of debate about the next major Boston-area highway project. The compromise plan managed to please most of the legions of neighborhood activists and advocacy organizations that had been working to shape it.

A little more than a year ago, Transportation Secretary Stephanie Pollack announced an ambitious reconfiguration of a tight stretch of land alongside the Charles River, to bring the Massachusetts Turnpike down to ground level through Allston and to elevate Soldiers Field Road above it.


“I think it’s very fair to say there are second thoughts,” said Emily Norton, executive director of the Charles River Watershed Association, which advocates for a clean river. “Saying the devil’s in the details is a cliche for a reason. That is always the case. And we did not have all the details.”

In permitting documents filed last year, officials outlined the potential disruptions. The turnpike is expected to be reduced to three lanes in each direction during the project. And for up to half of its duration, one of the two tracks of the Framingham/Worcester Line of the MBTA’s commuter rail could be offline, possibly slowing service. To make room for all of the construction while keeping the roads active, a temporary Soldiers Field Road would extend more than 100 feet into the river at some points.

The Allston project is tentatively scheduled to get underway in 2022, though it could yet be delayed by the public input and permitting processes. Officials have not fully determined how it will be financed. But Governor Charlie Baker included authorization for $250 million for “pre-construction, planning, and early action” in an $18 billion transportation borrowing bill that he is pressing lawmakers to pass.


The project has many elements: straightening the turnpike where it curves through the neighborhood; opening up land for development by Harvard University; building a new West Station rail stop; simplifying the tangled spaghetti of on-ramps and off-ramps from the turnpike in Allston; and establishing more parkland and biking and walking infrastructure.

But the most challenging aspect has been settling on a design for the crowded stretch of land between the Boston University campus and the Charles that’s known colloquially as “the throat." It’s where the eight-lane highway and four-lane Soldiers Field Road are joined by railroad tracks and a bicycle-and-pedestrian path alongside the river.

For years, the state and advocates tussled over how best to fit everything, with community members emphasizing their desire to bring the Mass. Pike down from the hulking viaduct that has carried it through the area since the 1960s, arguing it’s a loud, unsightly barrier that tears the neighborhood apart.

Many coalesced around a proposal to put all of the infrastructure at grade level, with the potential to add platforms over the roads and railways to eventually create more open space. But Pollack found that would require filling in some of the river to fit everything — possibly running afoul of federal permitting rules. Instead, she settled on a “hybrid” approach that would bring the highway slightly below grade level while sending the narrower and less-busy Soldiers Field Road into the air, creating more public space along the river.


At the time, Pollack said the configuration struck the right balance between different priorities and created the best final design to “stand the test of time.” But she warned it would require "a long and complicated construction period that will disrupt travelers.”

The fiscally conservative Pioneer Institute has been among the many to sound alarms about the effects on commuters, arguing that at a time of highway disruption the state should add commuter rail service, not threaten to disrupt it by using only a single track.

Pioneer suggested last year that the state Department of Transportation “should select a construction plan that has the shortest reasonable project duration with the least adverse impact on commuters.” That may require returning to an earlier idea of putting both the highway and Soldiers Field Road at grade, the organization wrote.

Other objections have centered on the temporary road within the river, which officials believe is necessary to keep traffic moving while the project is built.

“For 400 years we treated the river like a dump, and now we’re talking about sticking a road in the river that we spent so much to clean. . . . I really think it’s not a road to be going down,” Norton said.

Norton also questioned whether it makes sense to lower the turnpike, citing concerns about flooding caused by climate change — a concern that Pollack raised when she was still considering rebuilding the highway on a viaduct.


Jessica Robertson, an Allston resident who has long served on a project task force, said putting Soldiers Field Road in the river for up to a decade may be more disruptive than a much smaller but permanent extension of the river bank that would have allowed for the all at-grade design, which was dashed last year because of the permitting concerns.

“I think they’re really skirting the line with saying something that’s [going to last] 10 years is defined as temporary," Robertson said.

She suggested officials may be able to fit everything at grade level without building over the river by reducing the highway to seven lanes, from eight.

Jacque Goddard, a spokeswoman for Pollack, said MassDOT is reviewing all public comment but declined to otherwise comment “out of respect for the process." Officials noted at a public meeting in November that construction plans are preliminary, and Pollack said then that the state was considering “creative ideas for trying to move more people on the Worcester [rail] line" during construction.

The project is expected to be discussed at a state transportation board meeting on Monday.

Few groups are calling for the state to trash the current design and go back to the drawing board. Instead, most are suggesting that the state continue considering other design ideas. In a permitting document filed late last year, officials said they were focusing primarily on the design that Pollack recommended last year and suggested that other options not be considered.


Some advocates say it may be possible to stick with the current design but significantly limit its impact. Rick Dimino, president of A Better City, a business organization that got its start during the Big Dig, said it’s pushing for “technical improvements” that could keep both rail tracks in use, with a smaller temporary road that still goes over the Charles, but not as far.

Fred Salvucci, a former state transportation secretary who in a December letter supported building a temporary road over the river, thinks Pollack may face pressure to at least consider other options because of the impact on the river and the commuting issues.

“People thought this looks great," he said. "They did not understand it meant being in the river for 10 years. The patient has to be able to survive the operation.”

Adam Vaccaro can be reached at adam.vaccaro@globe.com. Follow him on Twitter at @adamtvaccaro.