Traffic is seen at a standstill in the southbound lanes of the Third Street tunnel of Interstate 395 after protesters blocked traffic on Nov. 30 in Washington. (Katherine Frey/The Washington Post)

Federal authorities are considering a request to shut down two-thirds of a mile of Interstate 395 in the District — one of the busiest stretches of highway in the city — for more than a year so that a mammoth development project can be completed more quickly.

New York-based Property Group Partners says that if the highway is closed between New York Avenue and D Street NW for 15 to 18 months, it could cut in half the construction time of a $200 million deck over the freeway’s entrance that will support its 2.2 million-square-foot development there, Capitol Crossing.

Without full access to that portion of the freeway, the platform project could take at least three years to complete, require loud work at night and potentially endanger workers, the developer says.

(Readers weigh in on developer’s request to close portion of I-395 in D.C.)

But the proposal has raised concerns that it would cripple one of the Washington area’s busiest commuter thoroughfares — which carries as many as 90,000 vehicles a day — and worsen the region’s gridlock.

Proposed closings for Capitol Crossing construction. (Source:)

“This would be impacting tens of thousands of people . . . and it will have a cascading effect. All the vehicles that can’t be there are going to be forced onto other very crowded major routes in the city,” AAA Mid-Atlantic spokesman Lon Anderson said.

City officials and business leaders acknowledge that it would be painful but say the proposal is worth considering, based on the value Capitol Crossing will bring to the city.

Building the deck requires installing about 150 caissons along the median to support a network of steel girders. Jeffrey I. Sussman, president and founder of Property Group Partners, has told the Federal Highway Administration (FHWA) and the D.C. Department of Transportation that installing the caissons while the highway is in use would be hazardous and disturb nearby residents.

Under the proposal, exits to New York and Massachusetts avenues would be closed, leaving access to and from the highway through C and D streets. That would involve setting up detours, but Sussman said he figures that drivers would navigate around the closures until the highway can be reopened.

“People find their way who drive because they like to drive. They like to figure out how to do it,” he said.

FHWA officials have been quietly reviewing the developer’s request and declined to say whether it is likely to be approved.

But closing portions of a major highway for such an extended period would be unprecedented in the region. For example, when major work has been done on the Capital Beltway, parts of the road have been shut for brief periods in the overnight hours, but most times, a lane has remained open during the project.

Traffic gridlock is seen on Interstate 395 in the District in this file photo. A developer is asking that a portion of the highway be closed for more than a year. (Jason Reed/Reuters)

The only time the city shut a major commuter route in recent memory was the summer of 2007, when the Frederick Douglass Memorial Bridge across the Anacostia River was closed for eight weeks for an overhaul, creating headaches for motorists who use South Capitol Street.

Capitol Crossing represents the realization of a longtime dream for the city. Since the 1980s, the District has envisioned filling the 6.8 acres of mostly air space over the sunken I-395 corridor, hoping to reconnect F and G streets between Second and Third streets.

The project will comprise three new city blocks bounded by Massachusetts Avenue to the north, E Street to the south, Third Street to the west and Second Street to the east. In all, it would deliver five buildings for office, retail and residential uses, with the first building completed in 2017 and the rest within nine years.

The bridging over the highway overpass would reconnect neighborhoods split by the freeway and create a more vibrant community in the downtown’s eastern flank, supporters say.

“It is currently, and has been since the highway was introduced in the middle of the city, a visible and physical scar upon our fair city. It is also a pedestrian nightmare and an unproductive piece of real estate,” said Matthew Troy, the city’s director of real estate.

“There is going to be an impact, obviously. But if the impact can be shortened, it is something that we want to explore,” Troy said.

Rich Bradley, executive director of the Downtown D.C. Business Improvement District, an association of property owners, including Sussman’s company, said the project would help connect the Union Station area with downtown.

“It has always been understood that development was going to be built over those air rights,” he said. “But the project, in order to be built, has to at some point interrupt the traffic so crews can build the support columns for the development that will take place above it.”

Still, news of the proposal to shut down part of I-395 came as a surprise to some city officials.

D.C. Council member Mary M. Cheh (D-Ward 3), head of the panel’s transportation committee, said she wasn’t aware of the request until a reporter asked her about it.

“My jaw dropped at the idea of closing 395 — with the disruption that that would cause,” Cheh said. “I just don’t see how that could work in any way that wouldn’t be a nightmare.”

Traffic disruptions related to the project started in the area in April, when crews began to move and upgrade underground utilities. There were more disruptions in September, when crews began to close some lanes on H Street NW and Massachusetts Avenue NW between Second and Fourth streets from 7 a.m. to 10 p.m. weekdays and from 8 a.m. to 8 p.m. Saturdays. Besides lane closures, the project has forced bus stops to be moved.

Officials at the FHWA are studying the potential impact to determine whether granting the request is appropriate, the agency said. In November, the agency received two letters from DDOT inquiring about the request to close the highway and the southbound I-395 Third Street ramp to expedite the project.

DDOT spokesman Reggie Sanders declined to discuss what effect the closure might have or what the agency might do to mitigate the disruption.

“Part of this process involves determining the impact on traffic as a result of the requested closure,” Sanders said. “To that end, we await the findings of FHWA.”

DDOT and FHWA declined to provide copies of the letters that detail the developer’s request, saying that a reporter would need to file a Freedom of Information Act request.

Cheh’s office was told by DDOT that if the federal highway agency’s response is that the closure is feasible, there would be at least a six-month study of the likely impact and possible alternatives. At that point, the federal agency could decline or approve the request, and DDOT would then get involved in the decision.

“They better think this through very carefully,” Cheh said.

Hermela Bealfan, a Lorton, Va., resident who regularly uses the Third Street tunnel to get downtown, said that traffic on I-395 is already a daily ordeal and that she can’t imagine what it would be like if the small portion leading to New York Avenue is closed.

“Even if it is just one day, it will be a mess,” she said. “It is already a very, very hectic area. I was born and raised here, and I have never driven down there and not experienced traffic, except at two in the morning sometimes, if I am lucky.”

A closure, and even just lane closures, would frustrate drivers who have been dealing with other construction-related traffic problems on I-395. Bealfan, who travels to the District at least three times a week, says she’s had enough of the work at the Springfield Mixing Bowl and, more recently, the construction of the express lanes.

“Now they want to close the Third Street tunnel? No! That’s absurd,” she said. “They should just do the construction at nighttime like everyone else does in this area. And they should leave a lane open — at least one lane.”

But in some respects, Washington has been anticipating this work for two decades, said Bradley, of the Business Improvement District. Although road authorities have a difficult task, there would be gains from the project: a close to $1.5 billion investment that once completed could generate at least $30 million in property taxes while jump-starting development in the area.

The trade-off of closing two highway entrances for 15 to 18 months, instead of three years with intermittent changes and lane closures, is that the project can move forward faster, the impact on traffic end sooner and the scar of the decades of split communities can be healed, he said.

“We are sorry there will be inconveniences, but there is no way around it, unfortunately.”