The increasingly expensive plans to reinvent Salt Lake City's old main library into an arts and science museum have Mayor Rocky Anderson and City Council members set to square off this evening over how to cover the shortfall.

Anderson is asking the council to consider funding options for The Leonardo, for which voters in 2003 approved a property-tax boost to raise $10 million. Another $10 million in private donations later, and the museum is still coming up short.

"We have been struggling since the beginning with the cost of the building," Leonardo executive director Mary Tull said. "The architects have now come back with budgets that reflect the inflation state we're in now, which is horrendous, seismic and asbestos needs and (Leadership in Energy and Environmental Design) certification, among other things."

All that has pushed the cost to renovating the building up by an estimated $13 million. Some of the increases come from new, unexpected sources — LEED certification, for example, is now required of city-funded projects — while others are the result of rising construction costs and inflation.

Anderson hopes the council will use about $4.9 million from the sale of city property, including the old Hansen Planetarium building and a warehouse at the west-side International Center, and bolster that with an $8.2 million sales-tax bond.

But at least one council member, mayoral candidate Dave Buhler, doesn't like the idea of spending any more city money on The Leonardo.

"I think I would be very hard-pressed to put more city money in above what the taxpayers already agreed to do," he said, noting that today's council meeting will also include discussion of several other capital-improvement funding needs that the sales-tax money could go to instead.

Early discussion of The Leonardo's funding problems focused on the possibility of asking voters to consider another general obligation bond, to be covered by a property-tax increase. But Anderson said he prefers the sales-tax bond because instead of costing taxpayers more, it would mean finding places to cut spending.

"When you do a sales-tax bond, it means that you're going to be living within your means," he said. "It's easily doable within our budget. There's a motor-fuel excise-tax bond — two of them actually — that both expire in 2009, and the debt service on those bonds was about $100,000 more than what this bond would be."

But Buhler, who during his mayoral campaign has often stressed his friendly relationship with Republican state lawmakers, said he wants to see the city work with county and state officials to spread some of the cost burden among them.