Washington State Department of Transportation maintenance crews will close the Alaskan Way Viaduct for its semiannual inspections this weekend.

Since the 2001 Nisqually earthquake, the department has conducted a full inspection of the viaduct every six months to closely monitor any settlement or other signs of continuing deterioration. Transportation crews also conduct three-month visual inspections as an added safety measure.

"We follow an aggressive inspection schedule for the Alaskan Way Viaduct. Going out there every three months to check existing cracks and settlement gives us another way to ensure the viaduct remains safe for drivers," says Craig Yasuda with the department's Bridge Preservation Office.

The week following the inspection, the transportation department will begin work to strengthen the columns between Columbia Street and Yesler Way, where the viaduct has settled approximately five inches since the Nisqually earthquake. The transportation agency determined that the threshold for emergency repairs was six inches, but chose to make the repairs sooner because of a trend of continued settlement. The repairs will take about six months to complete, and will prevent the columns from sinking further into the soil. This is the first of the six safety and mobility projects designed to repair or replace more than half of the deteriorating viaduct.

"We're pleased to be starting construction on this important repair, and this is just the beginning of the work we have planned to improve safety. By 2012, we will have replaced or repaired the viaduct in both the north and south ends," said Ron Paananen, director of the Alaskan Way Viaduct and Seawall Replacement Program.