A GROUP OF TRANSPORTATION advocates sent a letter on Wednesday to all members of the Massachusetts congressional delegation urging them to press for federal funding for an all-at-grade I-90 Allston project.

The advocates, representing neighboring communities, the business group A Better City, the Conservation Law Foundation, the Sierra Club, WalkBoston, Transit Matters, the Kendall Square Association, and the Worcester Regional Chamber of Commerce, urged the delegation to press for funding for the I-90 Allston project in President Biden’s $2 trillion infrastructure plan, which includes $20 billion to help stitch together communities that have been split apart by highways and address “historic inequities.”

Rick Dimino, the CEO of A Better City, said the Turnpike as it runs through Allston seems to perfectly fit what the Biden infrastructure plan is looking to address – a highway dividing communities and cutting them off from the Charles River. “If there’s any example of this in the United States, this is it,” Dimino said.

The state’s immediate priority in Allston is replacing a crumbling elevated section of the Turnpike that runs through an area that has come to be called the throat – a narrow stretch of land between Boston University and the Charles River. There is also talk of straightening the Turnpike, opening a new T station in the area, and eventually building rail connections to Kendall Square and North Station. Much of the work will facilitate the development of a new neighborhood in the area being built by Harvard University.

State transportation officials have struggled to find a design that satisfies all the stakeholders and lately have said they may not have enough money to do anything beyond replacing the elevated section of the Turnpike.  Dimino said the Biden infrastructure plan and the powerful positions held by members of the Massachusetts congressional delegation offer a unique opportunity to do the project right.

But while most advocates are on board with the all-at-grade plan, not all of them are on board with the same all-at-grade plan.

In its own letter to the congressional delegation, the Charles River Watershed Association said it cannot support the approach taken by the other groups, describing it as “fatally flawed because it requires filling in part of the Charles River. Not only is this the harmful to the river, but it also faces significant legal challenges.”

The Charles River Watershed Association’s solution for fitting all of the transportation elements into the throat at ground level is to reduce the number of lanes on the Turnpike, freeing up space for railroad tracks and Soldiers Field Road. The association said commuting patterns have changed with COVID and the number of lanes will be reduced during construction anyway – so why include them in the project?

Dimino said the Charles River Watershed Association is misinterpreting the plan his organization developed with the city of Boston. He said the plan calls for no roadway elements in the river. He said the plan does call for reworking the river’s edge, which has deteriorated badly, and running a boardwalk out over the river for walkers and bicyclists.

“We see the boardwalk as a critical amenity to the river,” he said. As for the work on the shore of the river, he said it’s necessary. “We’re making the river better with a livable river’s edge,” he said.

In its letter, the larger group of advocates said they already have the support of Sen. Ed Markey and Rep. Ayanna Pressley, and are appealing to the other members of Congress to get on board.

The debate over the Allston I-90 project has quieted since November, when state officials put off a decision about a preferred design until this summer and indicated they may go with a new Plan B – rebuilding just the elevated section of the Turnpike in the throat area and leaving the rest of the elements for another time.