New York City officials say they need to erect a temporary highway next to Brooklyn Bridge Park in order to rebuild a half-mile section of the Brooklyn-Queens Expressway that’s been crumbling for years.

The city transportation department on Monday announced the highway’s triple-cantilever will be closed while it’s rebuilt and restored in the 2030s. The project to repair the two stacked roadways beneath the Brooklyn Heights Promenade is expected to last a decade.

The temporary highway above Furman Street will prevent major disruptions for the 130,000 vehicles that drive on the structure each day. It will also have two levels and be the same height as the current highway, according to the plan.

Officials said the entire project will cost as much $4 billion. They did not disclose how the work would be funded, but said it would not require federal money.

The plan marks the most significant infrastructure decision of Mayor Zohran Mamdani’s administration so far. The crumbling triple-cantilever has vexed the two previous mayors, and the new strategy is sure to draw pushback from neighbors who are wary of construction and anti-car activists who want to see the highway dismantled altogether.

A proposal to fix the BQE by using a temporary highway faced fierce opposition in 2018. Mayor Bill de Blasio’s administration abandoned that plan, which would have required a six-year closure of the promenade.

City Transportation Commissioner Michael Flynn said the construction will require the closure of sections of the promenade but the temporary roadway would be “tucked out of view” from the pathway.

Courtesy NYC Department of Transportation

The city DOT has made short-term fixes to extend the roadway’s life in recent years, like eliminating a lane of traffic in each direction and adding monitors to crack down on overweight trucks.

“ We’re running out of time to do those kinds of interim type repairs. We need something more substantial, more of a full rehabilitation,” Flynn said.

Under the new plan, city officials will embark on a massive construction effort that will last even longer than the one pitched under de Blasio.

City officials under Mamdani plan to start building the temporary roadway in 2030, which will divert traffic from the existing BQE between Atlantic Avenue and Sands Street. By 2032, they plan to begin fixing the triple-cantilever, with a goal of tearing down the temporary roadway and opening the restored highway section by 2040.

The city believes the temporary highway plan will prevent vehicles from clogging local streets.

The rusted rebar and cracked concrete holding up the triple-cantilever is visible to anyone walking beneath the structure.

Stephen Nessen / Gothamist

Officials said the plan will still force sections of the promenade to close over the course of construction, but they pledged to always keep at least one portion open.

City and state officials first started planning to fix the structure in 2006. The triple-cantilever, now 72 years old, was commissioned under former Mayor Fiorello La Guardia and urban planner Robert Moses.

It was an engineering marvel when it opened in the 1950s, but it has since corroded and fallen into disrepair. In 2018, city officials estimated the roadway would fail as soon as 2026 if nothing was done to shore it up.

The city transportation department under previous Mayor Eric Adams published concepts to rebuild the roadway, but never moved forward with an engineering plan.

The city’s newest plan focuses on construction basics: replacing deck joints, concrete, and rebar, as well as improving the drainage, railings, and lighting. Officials said the rebuilt structure is designed to last 40 years.

Last month, the transportation department announced plans to hire an assistant commissioner to oversee the work.

Stephen Nessen / Gothamist

“ What this really represents is the simplest, most expedient, lowest cost way to address the most immediate and urgent needs with this major piece of infrastructure while minimizing impacts on surrounding communities and leaving the door open to larger visions,” Flynn said.

The transportation department plans to begin preparing an environmental impact statement for the work next year, and aims to wrap up the city’s land review process in 2028.

“The structure’s safe right now,” Flynn told reporters. “But with the time that it takes to gear up for major work, we really have pretty much run out of time to start to take action. So that’s where we find ourselves.”