Nickels suggests tunnel with 4 lanes

With costs rising for a proposed tunnel to replace the Alaskan Way Viaduct, Seattle Mayor Greg Nickels has suggested the state consider reducing the tunnel from six to four lanes.

"Within the tunnel there are things we ought to look at: whether a four-lane as opposed to a six-lane makes sense, whether it would save enough money for people to lower concerns about overall costs, and whether it would carry enough traffic to make it a good investment," Nickels said Monday on KUOW-FM radio.

Nickels said he wasn't necessarily supporting a four-lane tunnel, "but it's something we ought to look at and see what the cost benefit would be."

But Ron Paananen, viaduct project manager with the state Department of Transportation, said the state is not considering a four-lane tunnel. It was one of the original proposals for the viaduct replacement but was abandoned.

The state proposes a tunnel with three lanes in each direction, with 10-foot shoulders on one side and 4-foot shoulders on the other side. Paananen said trimming the width of the shoulders could be a way to save money. "Our best opportunity for saving money is looking at the shoulders," he said, but he couldn't say yet what the new shoulders might look like.

Before the state narrowed its viaduct-replacement options to two — a tunnel and a new elevated structure — it was looking at five possible plans. One was a bypass tunnel, replacing the viaduct with a four-lane tunnel along the central waterfront and expanding Alaskan Way to six lanes.

Paananen said that idea was dropped because it didn't include ramps to Elliott and Western avenues and because it would have dumped up to 50,000 vehicles a day onto Alaskan Way.

Still, he said, a four-lane tunnel could be revisited because design work has scarcely been started on the viaduct replacement.

"Everyone is interested in making the tunnel as affordable as possible," he said.

Nickels' comments came just two weeks after a Seattle Times poll reported that just 25 percent of Seattle voters want to replace the viaduct with a tunnel while 51 percent want a new viaduct built.

Voters cited a growing unease over new cost estimates, an estimated $4.6 billion for the tunnel, or $1 billion more than the previous estimate. Rebuilding the viaduct is estimated to cost $2.8 billion.

Marianne Bichsel, an aide to Nickels, said the mayor thinks that with the new cost estimates the state should explore options to bring the costs down. The four-lane tunnel is one option, she said.

Paananen said a four-lane tunnel wouldn't save much money because the state would still have to build the two tunnel walls and would save money only in excavation and roofing costs.

"We're not talking billions in savings," he said.

A problem with a four-lane tunnel, he said, is that traffic coming into the viaduct from Elliott and Western avenues would have to merge into the two lanes coming out of the Battery Street Tunnel, which would be unsafe.

In other viaduct developments, a volunteer group of civil engineers will meet next week to review a viaduct-retrofit proposal offered by retired structural engineer Victor Gray.

In August, T.Y. Lin International, hired by the state to look at Gray's retrofit plan, said it had some merit but doesn't deal with the damage an earthquake might cause to the viaduct's foundation.

A team from the American Society of Civil Engineers, working with Gray, was asked to analyze the Lin report, and that review is expected to be completed sometime this month.

Paananen said the state is reworking cost estimates for a retrofit, which it initially said would cost about 80 percent of rebuilding the structure.

He called Gray's proposal "an incomplete retrofit," and said the state is looking to see what it would take to make a retrofit structurally sound.

"Given the public's interest in retrofitting, we need to continually satisfy ourselves that we made the right call," Paananen said.

Susan Gilmore: 206-464-2054