NEW YORK (Reuters) - Adding floors on top of New York City’s Port Authority bus terminal is a viable way to expand the massive, outdated structure, according to a team charged with reviewing the controversial project on Thursday.

The so-called “build in place” option is one of several being considered to increase capacity at the crowded travel hub, which operator Port Authority of New York and New Jersey says is the largest in the United States and the busiest in the world.

Replacing the overburdened 42nd Street bus terminal has been long discussed, but progress has been stymied by arguments over funding, placement, pollution, design and transparency of the planning process.

Proposals have included moving the station underground or pushing it further west, which would disrupt commutes for the many New Jersey riders who stream into the city each day.

Many question whether it would even be possible to keep the terminal operating while it undergoes a complete renovation.

Steven Plate, the authority’s chief of major capital projects, told board members that his review team determined the option “is potentially viable from a construction and operational perspective.”

Building up in phases would allow bus and pedestrian operations to continue during construction. A new fifth and sixth floors could be added first, with replacement of existing floors to follow, he said.

The approach has been used before on other projects, including at the bus terminal itself, the World Trade Center, the Hospital for Special Surgery and the Children’s Hospital of Philadelphia.

“It’s been done. It’s proven,” Plate said. “Been there, done that.”

The authority’s latest capital plan includes $3.5 billion for the project, but that is expected to be only a portion of needed funding.

“My initial reaction was, that’s impossible, keep a bus terminal operating for 240,000 passengers each day and actually do this,” said New Jersey State Senator Loretta Weinberg, who has long fought with the authority for replacement of the 67-year-old terminal. “But apparently you can.”

She said that if a build-in-place option could add enough capacity, “I think we in New Jersey would be happy to embrace it.”