Salt Lake City Mayor Jackie Biskupski told the City Council on Tuesday that there may be a way for light rail to reach an under-construction terminal at the Salt Lake City International Airport without breaking the bank, but council members wondered why she wouldn’t share more details.

What changed after a year of contemplating a much more expensive version of the project? The city previously hadn’t allowed the Utah Transit Authority to contemplate a street-level TRAX extension, UTA CEO Jerry Benson said after Biskupski’s Tuesday briefing.

Instead, planners had focused on an estimated $68.5 million proposal that would have elevated the TRAX line so that it met a skywalk to the new terminal, scheduled for completion in 2020. UTA said that was more than it could afford, while Biskupski had stressed the agency’s 2008 interlocal agreement to pay for the city’s chosen designs.

The “at-grade” extension is “going to be much more affordable,” said Benson, who added that the airport’s engineers indicated it might cost about $15 million — a quarter of the elevated TRAX plan. “This is a very positive development.”

Biskupski said she was “superexcited” about the new proposal. “It will compare very well to any service in this country, and it certainly is better than what we have today,” she said.

But Biskupski wouldn’t even tell council members whether the new proposal involved an elevated track, saying that Benson had directed her not to.

Benson said Tuesday that was an apparent “misunderstanding” — he had asked her not to represent UTA’s position on the extension, he said, but not to be secretive about the broad outlines of the plan.

Biskupski’s vague presentation led Councilman Derek Kitchen to repeatedly ask why more details weren’t presented to the council, which had requested more information and had privately contemplated using city funds to help pay for the $68.5 million proposal, when it was thought that the alternative was to stop the TRAX line 1,200 feet short of the terminal.

“Are you aware that this body is entitled to the same confidential information as the executive branch?” asked Kitchen.

Councilman James Rogers asked Biskupski: “Yes or no, is it going to be elevated to the second level or not?”

“We have been asked to keep this confidential,” she said, adding that UTA needed to present an analysis to its trustees.

“I‘m trying to talk to Jerry a little about this, because I’m hearing your concerns,” she added later.

Later, at Tuesday night’s formal council meeting, Chief of Staff Patrick Leary said Biskupski had received a call from Benson “during the briefing” and that the council would receive additional documents about the proposal Wednesday morning.

Benson said Tuesday that an “at-grade” extension previously wasn’t contemplated because it would impinge on taxiways on the north side of the facility, and previous Airport Director Maureen Riley had “said it wasn’t acceptable.”

Biskupski told the council the city had gone “back to the drawing board” after Riley’s retirement this summer, under interim Director Russell Pack.

The UTA’s board of trustees next meets Sept. 27.