The Fairfax County Board of Supervisors is going to raise the taxes of residents of Tysons Corner to help pay for a $3.1 billion makeover of the area. The only question is how it will do it.

The board on Tuesday focused on two tax-raising options. One would immediately raise residents' real estate taxes by 7 to 9 cents, costing the average homeowner as much as $720 a year. The second would phase that tax increase in over several years. Either way, residents would be paying the higher taxes for more than 30 years.

The county staff recommended putting the full tax increase in place immediately because it would raise more money more quickly.

Several board members, however, expressed a preference for the phased-in option, saying it could make it easier on residents and businesses in Tysons who are helping to underwrite the cost of building new roads and other improvements in the redeveloping area.

"We've got to find some way to ramp up" the tax increase, said Supervisor John Cook, R-Braddock. "To implement the same high rate starting now, when the greatest number of taxpayers aren't yet in the [Tysons tax] district, doesn't make sense."

Supervisor Linda Smyth, D-Providence, one of two board members to vote against the take hike, voiced concerns over imposing higher taxes on residents and businesses now for projects that may be delayed or end up costing far more than expected.

"Our crystal ball is only so good," Smyth said. "We have seen costs have the ability to go up."

The board voted last month to increase taxes on people living in the Tysons area, after deciding that, despite a public outcry, residents should join Tysons area business owners and developers in helping to finance the needed improvements.

Del. Mark Keam, D-Vienna, tried to exempt Tysons residents from the tax hike, but legislation that would have done so died in the General Assembly.

"We passed this knowing it would affect residents, knowing that the General Assembly wouldn't pass an exemption," said Supervisor Pat Herrity, R-Springfield, who also opposed the tax increase. "It's a little too late to be backpedaling on this now."

About 22 percent of the Tysons tax district is comprised of residents. Along with businesses and developers, they will help the county raise $253 million to fund road improvements in what the county hopes will be its new urban downtown.

The board will decide on a tax plan on April 30.