Members of the Seattle City Council are ready to prepare a ballot measure asking city voters this spring if they are willing to pay extra for a waterfront tunnel or would they prefer a new elevated highway that could be paid for with existing financial commitments.

City Council President Nick Licata and Councilmember David Della jointly announced their goal to hold a citywide vote March 13. Last month, Governor Christine Gregoire called on Seattle city voters to pick a solution to break the impasse between the two options.

The ballot measure proposed by Licata and Della would include a cost comparison between the two alternatives. A new viaduct would cost an estimated $2.8 billion. A cut-and-cover trench is estimated to cost $4.6 billion.

The explanation would include the fact that $2.4 billion has been committed to the project.

"We have to be honest with Seattle voters about the additional $2 billion needed to build a tunnel," Licata said.

Della wants a vote soon because of earthquake risk.

"The quicker the vote, the quicker we get it built, reducing the likelihood of casualties" Della said.

Meanwhile Councilmember Jan Drago has doubts about a public choice between a tunnel and a new viaduct. Polls show the city is split on the question.

"I don't think it does any good to have an indecisive advisory vote by the people," Drago said. She is looking for an alternative proposal that would be acceptable both to tunnel advocates and viaduct proponents.