This should come as a surprise to precisely nobody—and yet there’s still something shocking about this article from Mike Lindblom at The Seattle Times:

More than three years after state lawmakers approved the Highway 99 tunnel, officials have yet to figure out how they can collect tolls for construction without clogging Seattle streets…One scenario, with tolls from $1 off-peak to $3.25 peak each direction, would raise $200 million for construction but divert one-third to half the daily traffic, said an official with access to the details… “It really is important to all of us we not cause diversion,” [House Transportation Committee chair Judy] Clibborn said. “I have been out telling everyone to count less on money that comes from tolling, and think of tolling as a lower amount, that covers operations and maintenance.”

Back in February, the state announced that it was cutting its tolling revenue forecast by half, from $400 million to $200 million (see page 9 of this pdf). And now, just a few months later, we’re already being conditioned to see $200 million as an upper bound—with actual revenues potentially falling far lower, meaning that the people who actually drive through the tunnel may prove willing to pay less than 5 percent of the overall cost of replacing the Viaduct.

Yet as we’ve said before, the fact that tolls cause traffic diversion is hardly new news. WSDOT’s own Final Environmental Impact Statement for the tunnel, published last July, said:

Tolling would cause vehicles to divert from SR 99 to other nearby roadways…the bored tunnel is expected to result in a daily diversion rate of about 40 percent for all vehicle classes.

Diverted traffic is something of an open secret: everybody knew about it, but nobody who supported the tunnel wanted to discuss it in public. (We did, but it felt like howling in the wilderness.) But now that the project is moving forward, the chickens are coming home to roost—and the state has to actually figure its way out of the mess it’s created.

And financially, it really is a mess. Reading the tea leaves, it looks to me as if any toll on the tunnel will create significant diversion—possibly enough to create havoc on city streets, particularly in SoDo and Pioneer Square. Remember, those places will already have to deal with major traffic increases from people trying to get into and out of the center city, because the tunnel has no off-ramps downtown.

So to my eyes, it looks like it’s just a matter of time before the state starts laying a glide path to eliminate tolling entirely. Given the configuration of the tunnel and the many toll-free alternatives that drivers will have, it’s likely that any attempt to raise a significant chunk of change from tolls will automatically create huge and costly problems with traffic diversion. So if we’re already hearing that $200 million is the high water mark for toll revenue, I expect that we’ll pretty soon start hearing talk of a lower bound of $0.

Meanwhile, as Lindblom points out, “The Port of Seattle pledged $300 million but has yet to deliver money or a binding financial plan.”  So between tolling and the port, that’s somewhere between $500 million and $700 million missing in action. And that means that the tunneling machine might be boring through more than dirt—it could be boring a hole through the state transportation budget as well.