The renovation plan for turning the old Salt Lake City Main Library into the Leonardo science and art museum didn't have enough in its budget to cover the contingencies that have arisen. As expected, turning an old building into a new building is more expensive than starting from scratch. A record-setting surge in construction costs was unexpected.

Now, four years after city voters approved a $10 million property-tax bond to finance the project and private donors kicked in a matching amount, the city is short by a whopping $13 million.

That probably surprises the 61 percent of Salt Lake City voters who in 2003 bought the city's sales pitch for a new home for the Utah Science Center, Global Artways and Center for Documentary Arts. They might suspect the city threw them a sneaky curve, purposely underestimating the cost to win their support.

One City Council member, mayoral candidate Dave Buhler, blames Mayor Rocky Anderson. Buhler says Anderson is irresponsible in pushing for a sales-tax revenue bond, with a 20-year repayment that would boost the debt service for the project to about $1 million a year, to make up the difference.

We don't believe there is any skulduggery or negligence to blame for the ballooning price tag. Certainly none has come to light. Still, the City Council should stick as close as possible to its original deal with voters, making up the shortfall at least in part by imposing again on the generosity of private donors. After all, a deal is a deal.

We endorsed the original Leonardo proposal and still believe it a worthy project. With Utah's extraordinary building boom, the costs of materials and labor have quite naturally mushroomed during the past four years, probably more than could have been foreseen.

Perhaps too little was budgeted for inflation, seismic retrofitting and asbestos removal, and for meeting stringent environmental standards set by the mayor.

But quibbling about what should have been doesn't help at this point. The question is: Should Salt Lake City residents pay more than double the original Leonardo sticker price? We tender a qualified yes, but only after all other funding options have been thoroughly exhausted.