A half dozen people waved black and yellow signs reading "Rebuild Viaduct, No Tunnel" at the traffic on Fourth Avenue at City Hall Thursday afternoon.

Gene Hoglund, who represents Working Families for an Elevated Solution on the viaduct advisory committee, organized the rally. Bud Shasteen, who lives in High Point in West Seattle, handed out flyers.

On them a chart compared the state's estimates for replacing the viaduct, against what the Viaduct Preservation Group estimates a retrofit will cost

"Our goal is to get Miyamoto again to do a study on the retrofit," said Shasteen

At the Alaskan Way Viaduct Stakeholders Advisory Committee meeting later that afternoon the state did just that.

"We have taken the retrofit off the table," said Dave Dye, deputy secretary for the Washington State Department of Transportation, "but we will do one more piece of due diligence."

In July 2006 the engineering firm Miyamoto International considered external braces and dampers as part of a retrofit, a design by retired engineer Victor Gray and the Viaduct Preservation Group. In that study Miyamoto was not asked to consider foundations or soil conditions beneath the viaduct.

It will this time. The state has contracted the firm to evaluate the full plan.

"After 10 years of conversations and many independent experts, (we've been told a retrofit) is not fiscally responsible," said Dye. "But if we get a 'wow' factor, a 'We've never thought of that,' we will bring (the retrofit) back."

The viaduct advisory committee continues to evaluate eight other scenarios to replace the viaduct: two configurations of elevated roadways, three tunnels, and three surface-only options.

The retrofit failed to meet guidelines for public safety and fiscal responsibility.

Andrew Taylor, with KPFF Consulting Engineers, reviewed 15 studies, back to 1995, on the vulnerability of the viaduct and the feasibility of a retrofit. He found the viaduct structure was "deficient" and in some cases already "failing."

After the 2001 Nisqually quake shear damage appeared at some joints, where beams began splitting away from columns. Chunks of concrete popped off the structure, which engineers call "spalling," revealing rusting and broken rebar inside. Chlorides from the sea salt in the air penetrate the concrete, corroding and weakening internal metal structure.

In a retrofit columns may be encased in steel jackets and beams wrapped in carbon or fiberglass and resin. But wrapping does not strengthen the knee joints to the upper deck, nor the "tee" joints to the lower. Reports say they must be replaced.

While their joints are being replaced, the girders and decks must be supported by temporary structures, eliminating parking and closing lanes.

"It's not work than can be done on nights and weekends," Taylor said. A retrofit would involve seven to eight years of construction, with closures of the entire viaduct.

Studies also reported weakness in column foundations. Injection of grout around the footings could stabilize soil subject to liquefaction, which is the tendency for loose fill to behave like liquid during an earthquake.

But in a quake pilings can lose adhesion with surrounding soil. The weight load transfers from the sides of the pilings and concentrates on their tips. Later jet grouting can't redistribute that load.

If the seawall fails and the fill dirt spills into Elliott Bay, jet grouting may not keep the viaduct from following.

New pilings and foundations for the sinking four columns between Seneca and Yesler streets cost $5 million. The viaduct has nearly 400 columns, although the southern mile of the structure will be replaced in a separate project beginning in 2009.

And despite the fixes, a retrofit still doesn't address the narrow lanes, the lack of emergency shoulders, and the inadequate merge lanes, which plague commuters now.

Engineers estimate a retrofit could extend the life of the viaduct only 25 years. A new structure will be designed to last 75 to 100 years.

Federal standards were updated this year requiring structures to withstand 1,000-year earthquakes. The Tacoma Narrows Bridge and the Sound Transit light rail are built to an even higher 2,500-year standard.

The viaduct, according to the seismic vulnerability report by Parsons Brinckerhoff last November, has a one-in-10 chance of collapsing in an earthquake in the next 10 years.

In September 2006, the Washington State of Transportation estimated the cost of a new elevated roadway, replacing all 2.2 miles of the viaduct, would be $2.828 billion. That November, T.Y. Lin International estimated a retrofit, using Victor Gray's design, would cost $2.268 billion. That is 80 percent of the cost for a new structure.

Estimated costs for scenarios still being considered are expected this autumn after computer modeling of traffic patterns show the strengths and weaknesses of each.

Matthew G. Miller is a freelance writer living in West Seattle. He may be contacted through bnteditor@robinsonnews.com.