SEATTLE – A recent Alaskan Way Viaduct inspection found that a section of the elevated roadway had settled an additional quarter of an inch, or a total of 43/4 inches since the 2001 Nisqually earthquake, state transportation officials said Wednesday.

No structural damage was found, the state Department of Transportation said in a news release.

“The viaduct is still safe for drivers. But if settlement continues we will need to make emergency repairs,” said Jugesh Kapur, state bridge engineer.

In 2004, the Transportation Department determined that if the columns in the settlement area – near Colman Dock – subside a total of 6 inches, repair work would be needed.

Weekend inspections have been conducted every six months since the 6.8 magnitude Nisqually quake rattled the viaduct, causing $3.5 million in damage to the structure that carries Highway 99 along the downtown waterfront.

When Mayor Greg Nickels heard the results of last weekend’s inspection, he again pressed for replacement of the aging structure with a tunnel, an approach now projected to cost $4.63 billion.

“Time is running out on this deteriorating structure,” Nickels said in a statement. “The latest settling highlights the need to get moving on replacing the … viaduct with the preferred option of the city – a cut-and-cover tunnel.”

The mayor portrays the tunnel option as a once-in-a-century opportunity to transform downtown Seattle by removing the towering concrete structure that stands between the city and its waterfront.

But costs for that approach continue to rise, worrying residents.