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Transportation

May 5, 2010

Independent study confirms severe deterioration of South Park Bridge

Engineering review confirms need to close bridge for public safety

An independent engineering report has confirmed what King County engineers have already determined – the South Park Bridge is in such poor condition it can no longer be safely used by the public. The bridge is set to close June 30.

The study, conducted by engineering consultant HNTB Corporation, concludes there is insufficient evidence that the bridge can be operated safely in its present condition. Engineers believe the remaining structural capacity to support both the weight of the bridge and the estimated 20,000 vehicles that cross the span each day is extremely limited. Further, based on a review of bridge components that can be visually observed, it is highly likely the bridge foundation buried beneath the Duwamish River is also severely deteriorated.

The study cites other deficiencies, as well.  The two bascule piers are shifting on their foundations causing the giant bridge spans to be misaligned. Steel members on the bridge piers that sustain high loads when the bridge opens and closes are attached to concrete that is disintegrating and cracking.  County bridge engineers now believe many of the structural problems being identified are a result of poor construction nearly 80 years ago.

In summary, the study concludes that the condition of the bridge is such that it should be closed to vehicular and pedestrian traffic in the near term before additional deterioration compromises its ability to safely support traffic loads.  Therefore, closure of the bridge on June 30, 2010 is reasonable and prudent.

Growing movement for financing of replacement bridge

While closure of the bridge for life-safety issues is now imminent, King County Executive Dow Constantine has made financing of a replacement bridge a top priority.

“I am committed to working quickly on a realistic funding plan to replace this transportation lifeline,” said Executive Constantine. “We have brought together a diverse coalition of community stakeholders to help us make a strong case for a new bridge. With regional leaders supporting a financing plan with significant state and local contributions, we can position ourselves to compete for federal dollars and other revenue sources.”

Planning to focus on minimizing impacts of bridge closure

While work continues to identify financing for a new bridge, the county’s transportation department has been aggressively working with the city of Seattle and others on plans to help minimize service disruptions during the three or more years it will take before a new bridge can be constructed. Those planning efforts will focus on:

  • Improvements being made, such as signal timing and signage, to minimize congestion and traffic impacts;
  • The latest plans for how Metro Transit buses will be re-routed after the closure;
  • How police, fire and emergency services will be coordinated; and
  • Strategies to minimize the impacts of the closure on businesses in the community.
The bridge is also a major regional freight corridor carrying 2,800 truck trips per day.  It serves one of the largest industrial and shipyard complexes in Washington and is used to haul freight to King County International Airport, Port of Seattle, the Duwamish waterfront, rail facilities, and the industrial areas of Kent and Auburn.

The condition of the bridge is so poor that it has a sufficiency rating of 4 out of a possible 100, making it the worst heavily traveled bridge in the state of Washington.

For more information about these closure planning efforts, visit the bridge website or call the South Park Bridge Closure Line at (206) 263-9979.

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