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Seattle Releases Magnolia Bridge Study

Wednesday, June 12, 2019

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The Seattle Department of Transportation has released its Magnolia Bridge Planning Study regarding possible options to address the bridge’s aging qualities.

The study reveals four different alternatives ranging from $190 million to $420 million in expenses.

About the Bridge

The Magnolia Bridge (also known as the West Garfield Street Bridge), constructed in 1929 by builder/contractor J.M. Clapp, embodies a concrete warren deck truss, complete with fixed and approach spans.

The main span length extends 87 feet, while the total structure length is 3,008 feet. The bridge also has 15 main spans and 50 approach spans.

Seattle Municipal Archives, CC-BY-2.0, via Wikimedia Commons

The Magnolia Bridge (also known as the West Garfield Street Bridge), constructed in 1929 by builder/contractor J.M. Clapp, embodies a concrete warren deck truss, complete with fixed and approach spans.

Nearly 30 years after the structure was built, a new grade separation structure was installed on the east end of the bridge. Then, from 1960-61, two more projects were completed to strengthen the west half of the bridge by installing steel cross bracing at six locations on the structure and various steel trusses for deck slab stiffening.

In 1974, the eastern half of the Magnolia bridge was retrofitted with steel trusses, much like the rehabilitation completed in 1961. In the '90s, the bridge received further rehabilitation: adding new ramps in 1991 and correcting landslide damage in 1997 through the installation of new steel cross bracing and deck support structures.

On Feb. 28, 2001, the Nisqually earthquake hit the Seattle area, bending almost half of the bridge’s total concrete lateral braces beyond repair. The braces were replaced with tubular steel bracing that same year.

Today, it’s reported that the bridge serves 17,000 ADT and three King County Metro bus lines, averaging about 3,000 riders every weekday.

The Plan

In 2017, the Levy to Move Seattle funded a 10-bridge planning study that included analyzing the 90-year-old Magnolia Bridge for various transportation scenarios, environmental impact, mobility, access, cost, construction duration and ultimately impact.

On June 6, SDOT held a community engagement meeting to discuss the In-Kind Replacement—a recommendation made in 2006 from a four-year planning study—and three alternatives.

The possible project routes include:

  • Alternative 1: A new Armory Way Bridge into Magnolia and a new Western Perimeter Road to Smith Cove/Elliot Bay Marina ($200 million to $350 million);
  • Alternative 2: Improvements to the existing Dravus Street connection into Magnolia and a new Western Perimeter Road to Smith Cove Park/Elliott Bay Marina ($190 million to $350 million);
  • Alternative 3: Improvements to the existing Dravus Street connection into Magnolia and a new Garfield Street bridge to Smith Cove Park/Elliot Bay Marina ($210 million to $360 million); and
  • Alternative 4: In-Kind Replacement of the existing Magnolia Bridge adjacent to its current location ($340 million to $420 million).

According to a technical memo released by consultants SCJ Alliance (Lacey, Washington), the two options that performed best among all comparison metrics and sensitivity analyses were Alternatives 1 and 4.

What’s Happening Now

Following last week’s meeting, K5 News reported that the community favored the most expensive option, Alternative 4. However, over the last decade, funding has failed to be identified to advance the alternative beyond 30% design.

Transportation officials have also gone on the record to say that the city doesn’t have enough money for any of the options without significant outside investments from state or federal partners.

According to former Seattle Mayor Mike McGinn, all the proposals under consideration run in direct opposition of the city’s climate goals as well.

“SDOT refused to consider any bridge replacement option that did not facilitate a dramatic increase in driving,” Mcginn Tweeted out last Thursday.

“Does our city government care in the slightest about climate change? They are planning on—indeed planning for— increasing our carbon emissions. Disgraceful.”

Other members of the community also expressed worry that the city could create its own fifth alternative, being that the Magnolia Bridge would be demolished and no alternative routes created.

While the debate continues, SDOT is working with the community and other agencies to propose creative funding ideas and transportation crews are continuing to complete regular inspections on the bridge in question.


Tagged categories: Bridges; Bridges; Construction; Department of Transportation (DOT); NA; North America; Program/Project Management; Project Management; Research; Upcoming projects

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