Report shows DOT reversed its course on 4-lane tunnel

A previously unreleased report shows that when the state's Alaskan Way Viaduct project team examined a four-lane-tunnel concept in January, the group thought the tunnel could handle the expected traffic.

Since then, the state Department of Transportation (DOT) reversed course, concluding Feb. 13 that the option nicknamed "Tunnel Lite" — in which cars would use the shoulders as exit-only lanes at peak times — would be unsafe. Gov. Christine Gregoire promptly declared she would only support a $2.8 billion six-lane elevated highway.

Staffers in the pro-tunnel administration of Seattle Mayor Greg Nickels say they're outraged the DOT didn't mention the 50-page report during weeks of intense public debate. A state DOT administrator called the report relatively insignificant and said the issues it covers have been aired in public.

The city is struggling to save the tunnel from political doom as ballots go out to city voters this week. Voters will be asked whether they prefer replacing the viaduct with a tunnel or an elevated structure. Ballots in the all-mail advisory election must be postmarked by March 13.

The state team's review began Jan. 8, with a plain four-lane tunnel quickly discredited. The next day, engineers started talking about allowing traffic on the shoulders during peak times. They called the idea Flex-6, because the tunnel would become six lanes at rush hour.

At Gregoire's request, the review stopped Jan. 12.

The team's report listed several safety "advantages" of the plan.

The shoulder would be available for emergency use when most crashes occur, which is at night and off-peak times, the team said.

Also, the report said collisions "appear more highly correlated to ramp congestion and non-standard merges than lack of shoulders," so the proposed tunnel would be safer than today's viaduct, which has a left-side onramp and a left-side offramp southbound. (A new tunnel would have no ramps in the mid-downtown area.)

The team's report recommends a 45 mph basic speed limit, while the city says speeds would be 35 mph when cars ran on the shoulder. Many U.S. tunnels have narrow shoulders or none at all. Reduced speeds would compensate for a lack of room to pull over, and for limited sight lines around curves.

David Dye, DOT urban-corridors administrator, said: "Why would you spend $3 billion on a brand-new facility, in a major public investment, and limit the speed to 35 mph? When you're on the witness stand testifying in the tort case, because somebody ran into somebody and there's an injury, how do you justify that? We're about safety, safety — oh, and the third priority, safety."

About 110,000 vehicles now travel the viaduct per weekday. "The Flex-6 tunnel would provide sufficient capacity to meet demand throughout the day," the report said.

Last week, state Transportation Secretary Doug MacDonald concluded the tunnel may work in theory but in real life would be clogged by collisions and breakdowns. The city has accused the DOT of bowing to political pressure from anti-tunnel legislators.

"I think it [the report] pretty clearly shows that in terms of capacity, safety, that there are no fatal flaws to this approach," Deputy Mayor Tim Ceis said. "It appears to me, WashDOT has deliberately hid the ball."

The project team includes the state DOT, the Seattle Department of Transportation and about 30 private firms, led by engineering giant Parsons Brinckerhoff, which potentially could benefit from future design contracts.

The team called the new tunnel concept, estimated at $3.4 billion, financially "less risky" than a bigger six-lane tunnel the state and city proposed last year because the smaller version could be built more quickly.

The report and scores of documents, which the city got last week through a public-records request, show the team applying material prices and risk analyses from earlier versions, to get a $3.4 billion estimate for Flex-6 — the figure the city put forward weeks ago.

But, the report cautions, "because of the short time frame, the Project Team was not able to produce definitive conclusions as to either the feasibility or the cost of the City's proposal."

In the Feb. 13 memo to Gregoire, the DOT did not provide a cost estimate. Agency officials said there wasn't time.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com