"We still have a long ways to go in this process," said Craig Stone with WSDOT.
The report Wednesday presents four new tolling scenarios and comes after months of number-crunching.
But so far, nobody's come-up with a toll that hits the sweet spot: not too high and not too low.
"No, this is a process and we will be working through the summer on refining this with this committee," Stone said.
The DOT worries a toll set too low won't generate the state's target of $200 million needed to help pay for the tunnel. A toll set too high means instead of using the tunnel, drivers will divert to I-5 or Downtown Seattle, jamming up First and Fourth Avenues trying to get to north and south to and from work and home.
"It's a balance from that stand-point," Stone said.
Stone says half of the DOT's tolling scenarios don't generate the $200 million needed, while the other half do. But none of them may cover another $160 million for operations and maintenance, up to $85 million for insurance, and $190 million for repair and replacement costs.
The advisory committee will have to figure out if the tolls should pay for those extra costs or not. But if they decide they won't, Stone says WSDOT may not be able to sell the project to the bond market to borrow money to help pay for the tunnel.
The DOT says there's plenty of time to figure it all out. In the meantime, Bertha -- the massive tunnel-boring machine -- is on her way from Japan to begin digging. She'll be here next month.