Cross the bridge along Neponset Avenue in Dorchester into Quincy and it’s a quick ride to Squantum, a hilly peninsula filled with tightly clustered homes. A causeway leads to Moon Island and a bridge once allowed drivers to continue to Long Island.

“We’re an isolated little community out here served by one road coming in,” said Jim Stamos, a longtime resident and realtor in Squantum.

“We’ve suffered for years with the buses and trucks that service Long Island,” said Stamos. “It was a constant flow of traffic — lots of ambulances.”

A homeless shelter and a smattering of addiction treatment programs were located on Long Island until four years ago when the original bridge was deemed unsafe and ultimately demolished.

“The traffic is way down,” said Ralph DiMattia, the local sail maker. “The last thing in the world we want is to see a bridge.”

Mattia’s shop is a stone’s throw from the harbor and a view of downtown Boston but Squantum still has as small-town feel and Jim Stamos is convinced that — at a time of sky-high real estate values — a new $90 million bridge will change everything.

“Once they rebuild the bridge that’s the conduit to development out on the island,” said Stamos. “I think it will be high end housing, I think it will be a hotel.”

The island belongs to Boston, but city officials insist the plan isn’t to bring in development, but to bring back one of the things that was there before and is desperately needed now: help for opioid addicts.

“It’s a crisis, no sugar-coating this,” said Jonathan Scott, the CEO of Victory Programs.

Scott knows Long Island well. Until the bridge closed, Victory Programs ran a 40-bed drug rehabilitation program for women there. It was, he recalled, an idyllic location — remote enough to offer women in recovery both safety and a separation from addiction triggers, yet close enough to allow them to transition back home.

The need for treatment has grown he said as the opioid epidemic has worsened, particularly in Boston.

“You speak to anybody who’s out there on the streets and they’ll says the same thing,” said Scott, “‘beds, beds, beds. We have no place to go’”.

Scott is among the key advisers helping Boston Mayor Marty Walsh’s administration plan for a recovery campus on Long Island. He imagines existing city-owned buildings will do the job.

“Other than a bridge,” said Scott, “it’s really ready set go.”

But the exact plans for Long Island are vague. The city is still soliciting ideas as it plans a campus flexible enough to deal both with current challenges of the opioid epidemic and potential future needs.

“It’s a once in a lifetime scenario,” said Marty Martinez, Walsh’s chief of health and human services, “the ability to take a comprehensive approach to create what is a response to an epidemic that we’re faced with.”

Could the cost of developing and running that campus be offset by private development?

“I can never say 'never,' obviously, there’s a lot of thing to think about with development,” said Martinez. “But, on the island, what we’re focused on is the creation of a recovery campus.”

Something Quincy Mayor Thomas Koch said could always change.

“Even if Mayor Walsh agreed to limitations, he leaves office a new mayor comes in, there’s over 200 acres at Long Island,” said Koch. “Once the bridge is built, what else will happen out there?”

He’s floating another idea for Boston to consider: instead of a spending $90 million on a bridge, fund a ferry service to Long Island. It’s an idea Boston says is too expensive — and impractical — to ever get off the ground.

Meanwhile, the bridge battle continues.

Quincy’s conservation commission has rejected plans for the new bridge, a decision Boston is now appealing. Koch believes the final decision on the bridge may rest with a judge. Quincy’s city council has earmarked $250,000 to pay for legal and engineering experts.

Marty Martinez, Boston's health and human services chief, indicated Boston is gearing up for a fight, too.

“The bridge," he said, "is getting built.”

Correction: An earlier version of this story misstated the amount of money Quincy has allocated for legal fees. The correct amount is $250,000.