SEATTLE - The Alaskan Way Viaduct has settled another 3/8ths inch, but ongoing repairs should keep the structure safe, the state Transportation Department said today.

The additional sinking was discovered during a semiannual inspection of the viaduct along Seattle's waterfront last weekend. Results are preliminary, but the state DOT says it appears the additional sinking brings the total amount of settlement to approximately 5 1/2 inches.

The columns continue to settle incrementally between Columbia Street and Yesler Way where repairs are nearly complete to strengthen several column foundations. No new structural damage was caused by the additional settlement.

Crews have been repairing and strengthening the viaduct since it was damaged during the Nisqually Earthquake in 2001.

"These four columns continue to sink gradually and that's why we began the repairs to the viaduct last fall," said DOT Deputy Secretary Dave Dye. "These repairs are going to give us a strong column foundation that will keep the viaduct safe for drivers until we take it down in 2012."

The Transportation Department has been monitoring this section near Columbia Street and Yesler Way since 2002. In 2004, DOT determined that if the columns in this area should settle a total of six inches, repair work would be needed. Because of the continued settlement trend, WSDOT decided to move forward with repairs sooner.

"We expected to see some slight settlement caused by the construction activity, but there are probably a number of reasons why the viaduct keeps settling in this location," said Harvey Coffman, WSDOT Bridge Preservation Engineer. "The viaduct was seriously damaged in the 2001 Nisqually earthquake."

WSDOT began repairs last fall to strengthen the foundations of the four columns.

Repairs involve drilling a series of steel rods deep into the ground into the stable soil surrounding the existing structural footings. The rods, called micropiles, are each able to carry a 95-ton load and will make a wider and stronger column foundation. The foundation work is expected to be complete at the end of April or beginning of May.

Some additional settlement may naturally occur after this work is complete.

This work is one of six projects planned to replace or repair approximately half of the viaduct by 2012. State DOT crews conduct visual inspections every three months and full inspections every six months to monitor the viaduct's condition and keep the viaduct safe for everyday use.