SEATTLE - Taxpayers may be asked to cough up more money to build a new 520 floating bridge - that is, if the regional transportation tax is approved by voters in November. 

Officials have been crunching the numbers, and even with the passage of a regional transit tax, there still may not be enough money to build a new floating bridge. 

A new 520 bridge will cost roughly $4.4 billion, but no one is sure how to pay for it.  The Seattle Post-Intelligencer estimates even with a gas tax, a toll and the possible R-TID (Regional Transportation Investment District tax from the November ballot) money, the project would still be at least $230 million short. And some believe another tax could be needed to replace the aging structure. 

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The state claims the current bridge would fall apart in the next major earthquake or windstorm.  Washington State Treasurer Mike Murphy has even floated tolling 520 and I-90 to bridge the financial gap. 

"If they're only tolling the 520, you're 30 percent short of paying off the project, because of the bypass effect because the toll would likely be so high," said Murphy. 

Governor Christine Gregoire calls any finance plan premature and that it's possible to use money once targeted for a new viaduct if the state eventually settles on the surface option there. 

The Seattle City Council is expected to weigh in on the debate as it takes up a resolution concerning the bridge at the council meeting Monday afternoon.