Fort Point Channel floodgate idea advances, but how to pay for it?

Estimates range as high as $767 million, but it could prevent billions of dollars of property damage during a catastrophic storm

Kayakers paddled along the Fort Point Channel on Aug. 14, 2021.John Tlumacki/Globe Staff

John Sullivan is getting people to believe that his bold idea to build a storm barrier across Fort Point Channel isn’t so far-fetched after all.

But can the Boston Water and Sewer Commission’s chief engineer find a way to pay for the vision he pitched nearly a year and a half ago?

That question looms large now that he has a price tag. A more aesthetically pleasing version, with swinging floodgates tucked away underwater, could cost up to $767 million. A less visually appealing alternative, with gates that rise vertically from the channel floor, could ring in at $459 million.

These eye-popping numbers can be found in a lengthy new report that outlines various stormwater control proposals along the city’s coastline. Sullivan started circulating the report, by engineering firm Hazen and Sawyer, earlier this month. All these projects — pump stations, underground storage tanks, and the like — could total more than $1.5 billion and take decades to build.

The priciest of these by far would be the Fort Point barrier. But the Hazel report makes the case that it could prevent billions of dollars in property damage if a catastrophic storm hits Boston when the tide is perilously high.

Most coastal resiliency efforts in Boston focus on keeping ocean waters out. Less had been said about the potential wreckage if rising seas prevent the city’s rainfall outflow system from working. Then Sullivan started sounding the alarm. He hired Hazen in 2021 to look at the most troubling coastline spots, places where drainpipes and a rising ocean would come into conflict.

Sullivan asked the engineering firm to specifically take a close look at the Fort Point Channel. Why there? Well, the channel happens to be a massive storm-pipe nexus. It accepts water from a big swath of downtown, South Boston, and Dorchester ― one that stretches across some 2,600 acres. And it shields about 800 acres from flooding. Consider what could happen if rain gets backed up there. Buildings ranging from Fidelity’s headquarters to Boston Medical Center to the Boston Fed tower could become islands amid the deluge. South Station could shut down, taking much of the public transit system along with it. The Big Dig? Think the Big Drink.

This design shows a way to create a Fort Point Channel storm-surge barrier as part of a new Northern Avenue bridge. Boston Water and Sewer Commission/Hazen and Sawyer

Sullivan made the rounds about 18 months ago to float the Fort Point barrier idea. It would turn the channel into a giant bathtub when a particularly bad storm looms. The gates would be closed at low tide, allowing room to store roughly 160 million gallons of rainwater as the tide rises on the other side of the barrier. The excess water would then be released once the tide waters recede. Pumps could be activated, in a pinch, to release some of the water earlier during a long-running storm.

The Hazen report’s timing is fortuitous for two reasons. The Army Corps of Engineers and City of Boston just launched a coastal storm risk management study to assess, in part, existing preparations and various projects that can mitigate storm damage. This study could open the door to more federal funds. Sullivan wants Hazen’s findings to be in the mix.

Then there are the shelved-but-not-forgotten plans to rebuild the old Northern Avenue Bridge, the deteriorating span across the channel’s mouth that was shut to cars in 1997 and closed off completely in 2014. Officials in the Walsh administration eventually settled on a flashy replacement design that could accommodate pedestrians as well as buses and emergency vehicles, along with a below-level plaza. They budgeted $100 million for the work, and a 2022 groundbreaking was promised.

Those plans were put on hold amid administration changes in City Hall and more pressing issues. It’s not clear whether the Wu administration will embrace the original design or go back to the drawing board. (Either way, inflation means the cost has assuredly gone up.)

The bridge discussions continue to percolate, but the barrier concept offers a new twist. Why not build the bridge and the barrier together, improving its aesthetics and perhaps attracting some money to help defray the cost? The Hazen report envisions this as an option. Even if the bridge never gets rebuilt, Hazen’s alternatives include some sort of pedestrian path that would connect the downtown side to the Seaport.

So what does Mayor Michelle Wu think? The administration, a spokesperson said, has a “strong preference for nature-based solutions that address sea level rise, rainwater flooding, [and] storm surge” but will review Boston Water and Sewer’s proposal to determine if it’s the right solution for the Fort Point Channel and surrounding areas. A “robust community engagement process” would be required before moving ahead, the spokesperson said.

The Charles River Watershed Association, too, would like to see more of an emphasis on nature-based solutions, aka green stormwater infrastructure, in addition to the “gray” kind Sullivan is suggesting. That said, executive director Emily Norton commended Boston Water and Sewer for taking on the significant threat of inland, rain-related flooding. You might even call this a watershed event: Norton said the Hazen report “presages a new era” in which the city’s existing storm-water management system, designed to drain by gravity into Boston Harbor, might no longer be effective amid rising seas.

A pedestrian crossed the Fort Point Channel on Seaport Boulevard in Boston. Craig F. Walker/Globe Staff/The Boston Globe

Likewise, Boston Harbor Now president Kathy Abbott praised Sullivan’s efforts. It could help prompt a more holistic approach to climate-change planning. But she also wants to learn more about any environmental impacts posed by the channel barrier.

Those possible impacts are also on the mind of Tom Ready, of the Fort Point Neighborhood Association. He seems more accepting of the barrier concept now than he was in late 2021. The neighborhood, he said, has had time to think about it. But he still wants to make sure the project doesn’t interfere with the channel’s natural ebbs and flows that remove much of the dirty water at the southern end of the channel.

Ready also raised the billion-dollar question: How to pay for it?

Sullivan remains convinced it can be done — likely through a mix of federal, state, and local funds. Probably some bonding, too. And maybe a new quasi-public authority could be created to oversee these and other harbor resiliency projects. A proposal of this size is beyond Boston Water and Sewer’s historic scope.

Sullivan doesn’t need to be here. A lifelong employee with 50-plus years in the department, Sullivan could be sitting on a beach right now. Saving Boston from a rainwater apocalypse would be the toughest challenge of his career. It also might end up being the most important one.