If voters approve a proposed $523 million bond issue to renovate the Astrodome and replace Reliant Arena, Harris County officials say property taxes likely would have to rise to make the resulting debt payments.

The recommendation to put the plans to a vote came Wednesday from the county's Sports & Convention Corp., the board in charge of county-owned Reliant Park. Consultants pegged the cost to replace the aging arena at $385 million and the price tag to renovate the Dome at $270 million.

Costs could be reduced to a combined $523 million by the use of tax credits, the consultants said. A cheaper option for the Dome would be to knock it down and turn it into a plaza for $64 million. None of those numbers include the $29.9 million the county still owes on the Dome, which hasn't been home to a professional sports team in 12 years and has been deemed unfit for occupancy since 2009.

Bill Jackson, the county's chief budget officer, said such a large bond issue likely would require a tax hike or deep budget cuts, particularly given other projects for which the county will need to sell bonds, such as a forensic sciences facility.

Financing $500 million over 30 years at 5 percent interest would require $28 million annually, Jackson said. For comparison, $28 million covers the annual costs for all but seven of the county's dozens of departments, not counting the commissioners.

"It would be very difficult with everything we that have on our plate right now" to issue $500 million in bonds without a tax hike, Jackson said. "It's a matter of setting priorities and figuring that out."

No great enthusiasm

A one-cent tax increase would generate about $26 million a year, Jackson said. That increase would raise the taxes on a $200,000 home by $16 annually, assuming the owner had a homestead exemption.

Precinct 3 Commissioner Steve Radack has said he would rather delay action on the proposal than see taxes jump. Precinct 4 Commissioner Jack Cagle said his constituents consistently tell him they want no tax increases, and said he'll be reviewing the report with that in mind.

Precinct 2 Commissioner Jack Morman said he does not believe enough time exists to educate voters about the proposal before November's election.

He also said he supports letting voters decide, perhaps next year.

"As long as we let everybody know, 'Hey if you approve this measure, it will mean a tax increase,' and they go ahead and approve it, well, that's the will of the people," Morman said. "I personally, as a property tax payer, would not vote for a tax increase, but if I'm in the minority, then democracy rules."

Commissioner El Franco Lee, whose Precinct 1 is home to the Reliant complex, said he has a "personal affection" for the Dome and said its debt will persist regardless. But he said the county must act reasonably and consider its budget.

"Now that we have the amount that the project will cost, everybody can digest it and determine if that's something we want to do at this time - all or part of the proposal," Lee said. "Commissioners Court has to deem it important and the public has to agree."

County Judge Ed Emmett said the Sports Corp.'s recommendation is only the beginning.

"The way it was trotted out, we're going to re-purpose the Dome and we're going to replace the arena with a new building," Emmett said. "If we're doing that, why don't we use the Dome for the purposes the arena was being used for? Because that would obviously cost less."

Private funding?

Emmett said he favors the idea of saving the Dome in some way now to preserve it for a great idea in the future, presumably privately funded.

Political consultant Joe Householder said the ballot item would be a tough sell this fall. But waiting may not help, he said. Unlike when voters approved bonds to build new homes for the Texans, Rockets and Astros, no team will be moving into the new Dome or arena.

"You really are going to have to do a hardcore sales job to convince people there's a payoff for them," he said. " 'Oh, it's a great new building and we can bring new conventions in' - that's a little bit too ephemeral."

mike.morris@chron.com