Concerns about The Leonardo as a viable use of the former Salt Lake City library has city leaders considering other options for the building.

Mayor Ralph Becker has instructed city staff to immediately begin exploring other possibilities for the building at 209 E. 500 South. The proposed arts, culture and science center is still an option — just not the only one.

Becker and members of the Salt Lake City Council are uneasy about the cost estimates and revenue projections in recently revised plans for The Leonardo.

The new proposal, sent to city officials last week, outlines scaled-back renovations that Leonardo officials say could be completed with the $10.2 million general-obligation bond approved by voters in 2003, which would allow the center to open in fall 2009.

"We believe this is the best plan for Library Square," Peter Giles, new executive director for The Leonardo, told the council during a work session Tuesday. "We'd like you to table any plans (to seek) new uses for the library, and we ask that you release the bond money so we can let The Leonardo flourish."

The bond requires the museum to find a matching $10 million in outside donations for programming, which has been secured, Giles said.

"The Leonardo has performed its obligation and is waiting for the city to do the same," he said.

The council hasn't decided whether it will release the bond money. Council members and city officials say the new plan needs to be analyzed closely before any decisions are made.

"We want to be good partners," said Jill Remington Love, council chairwoman. "But we can't be left running the museum. Two years from now, if it's not viable ... you will come to us to bail you out. That's our fear."

The Leonardo previously had been facing a $5.5 million funding gap, one officials in February said they proposed to close by selling naming rights to the building. The June 1 deadline to obtain those funds was extended by the City Council to Aug. 1, but no donor or sponsor emerged.

City staff and Leonardo officials worked together to present the project scope and funding plan to the council in February. It outlined three courses of action that required $3.1 million, $5.5 million or $8.3 million in additional funding.

The council expressed support for the $5.5 million option, which put the project price tag at $19.1 million.

Becker said he doesn't understand the discrepancy between the February cost estimates for essential renovations and those in the new proposal.

"To us, the numbers don't match up," he said.

Rick Graham, city public services director, said The Leonardo is now proposing upgrades that were not included in the lowest-level option in February, such as renovating the building's third floor and meeting the silver level of the Leadership in Energy and Environmental Design rating system.