CAMBRIDGE — Just rip out the decaying Riverside Park Dam like a rotten 127-year-old tooth.

That's what a city-led environmental study, six years and $340,000 in the making, is poised to suggest to Cambridge city council come February.

Tear it out and naturalize the Speed River through a nationally-celebrated park.

Kiss the mill pond and its iconic concrete goalposts goodbye. Enjoy the freer passage, improved water quality and faster flow of a maintenance-free future.

According to city engineer James Etienne, that's the preliminary preferred solution to the ongoing dam dilemma that's churned the political waters in Cambridge for the better part of a damnable decade.

Riverside without its dam?

"If you take away the dam, it changes the atmosphere of the park," said Mike Mann, a Preston city councillor who "absolutely" opposes naturalizing the river.

"It changes the character of the park," Mann said.

"When you look at Preston, where was the old post office? Where was the old fire station? Where was the old police station? Where was the old library? All those historical fixtures of the community are gone.

"If you take away the dam, you remove one more item from the heritage of the community. If you remove the heritage, you remove the identity."

Is the demise of the doomed-again dam a done deal?

"This is not the end point," Etienne said.

The two top-rated study options for the dam — rebuild, or rip out and naturalize — are still before Cambridge politicians just a year out from an election. Councillors, with vote-wielding save-the-dam devotees in their ears, can surely overturn any recommendation on the future of a dam still said to be in danger of imminent failure.

The fear remains that the dam could break apart and wipe out the 123-year-old wooden train tracks that run below the dam, carrying locally-made cars to the world.

"If it fails, all this becomes moot and it's all because of foot-dragging," said Carol Thorman, one of a thousand social-media members of the Friends of Riverside Park Dam and Mill Pond.

"Pet projects of council seem to be railroaded through very quickly. For whatever reason, this one has dragged on."

So as a $2-million pedestrian bridge prepares to open in Galt, the save-the-dam devotees are preparing for yet another public information meeting, the fourth of the process, next Wednesday from 6:30 to 9 p.m. at the Preston Legion on Westminster Drive.

They can ask questions and drive their points home, again and again.

"It's going to be a heated meeting," Thorman said.

They can talk money, if they like. Tearing down and rebuilding the dam would cost an estimated $6.3-million, with a 100-year life-cycle cost of $8.6-million.

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Just ripping out the dam and naturalizing would run $4.9 million, with a life-cycle cost of $5.1 million. Right now, the city is looking at earmarking $7.5 million for the Riverside Park Dam solution in the 2020 budget. Only $5 million was set aside four years ago.

Preston's sentimental heart says save the dam.

Colder calculations regarding sediment and water quality maintenance matters point to a future with no dam and no dangerous portage across a busy street for canoeists.

"A lot of the technical criteria lend themselves more to the naturalization," Etienne said.

Naturalization has supporters, too.

"There are some people who want that," said Donna Reid, councillor for the ward that includes Riverside Park. But the save-the-dam crowd often seems overwhelming.

"I don't get the same overwhelming feeling for those who want to naturalize it," said Reid, who prefers to listen more before declaring a preference.

"I can understand both points of view."

But few clearly understand the ownership of the dam. The province has pointed one finger at the heirs of the flour mill builders across the street and another finger at the city for its caretaker stance on the past decade.

"The city does not own the dam," Mayor Doug Craig said. "But the city, being a steward of the community and reacting to the community, is taking ownership of the issue."

And that issue of ownership will come with the burden of a political decision, one that could be put off until a new council is put in place.

Tear down a piece of historic Preston or opt for a fresh, natural approach.

"It's going to be a decision council's going to have to make," Reid said. "Because we can't do both."