May 6, 2020

Kraemer to repair West Seattle Bridge; task force develops evacuation plan

Image from SDOT [enlarge]

An interagency task force has determined a “fall zone” where a few land parcels would be evacuated in the unlikely event that the bridge becomes a safety hazard to those below it.

The Seattle Department of Transportation recently picked Kraemer North America to stabilize the high-rise portion of the West Seattle Bridge.

Kraemer is already working with the design team on the bridge, which was closed on March 23 after inspectors found expanded cracking. The contractor is developing plans for construction, equipment and material procurement, schedules and permitting. It also is helping with a forensic investigation, providing constructibility input to the engineering team and confirming repair estimates.

SDOT used its emergency contracting authority to pick Kraemer out of a group of six firms it contacted on April 13. Four of the six firms responded by April 15. SDOT picked Kraemer on April 21 and issued a limited notice to proceed on the following day.

SDOT said Kraemer is working without a contract under the emergency contracting rules, which allow work to begin before a contract is signed. Construction is expected to begin once design work is finished, permits have been obtained and customized materials have been procured.

Kraemer's initial repairs are expected to stop further cracking in the bridge's most vulnerable sections. The contractor will then replace the lateral bearings on Pier 18 at the east end of the bridge. Inspectors found these bearings were compressed and bulging outward. Bearings allow the bridge to move slightly due to thermal expansion and traffic loads.

SDOT has a three-phase repair plan for the bridge:

• Stabilize it by removing traffic and repairing the lateral bearings on Pier 18.

• Install temporary shoring while the team assesses construction feasibility, schedule and cost.

• Long-term repair.

SDOT is still trying to figure out if repairing the bridge is technically or financially feasible. SDOT director Sam Zimbabwe last month said the bridge wouldn't likely reopen until 2022 and the repair work would only restore about a decade of life to the span built in 1984.

A recent update from SDOT said the bridge remains stable and the growth of cracks has slowed since traffic was removed. Still, an interagency task force has put together an emergency response plan in the unlikely event that the bridge becomes a safety hazard to those below it. This plan includes an evacuation area of a few land parcels that the task force calls a “fall zone.”

The task force identified three possible scenarios:

• Immediate evacuation of a few properties below the bridge if daily inspections indicate enough change to warrant that. An SDOT blog post said the evacuation would be immediate, “though we could have hours or days before actual bridge failure.”

• Evacuation with one to five days' notice if new remote monitoring sensors, expected to be working mid-month, indicate enough of a change. The blog said, “If failure is anticipated, but not immediate, Seattle Fire Department and Seattle Police Department will clearly communicate, via direct site visits and other platforms, when evacuation must occur.”

• Controlled demolition, if the change in the condition of the bridge indicates the need to evacuate and demolish the bridge.

The task force is composed of the city of Seattle, King County, Washington state, Port of Seattle, Northwest Seaport Alliance, Coast Guard and Army Corps of Engineers.

SDOT said its Capital Projects and Roadway Structures divisions evaluated and rated the initial repair work submittals, including consideration of the city's previous experience with each contractor. It said Kraemer is an industry leader in segmental bridge repair and construction, as well as in concrete post-tensioning.

Kraemer won a $28.4 million SDOT contract last year to build a pedestrian bridge over Interstate 5 in Northgate. It also worked with the Washington State Department of Transportation on the nearby Duwamish River Bridge project.

WSP is SDOT's consultant on the West Seattle Bridge.