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Ballard Bridge Seismic Retrofit

Last updated on March 17, 2014

The Ballard Bridge Seismic Retrofit Project was finished 6 weeks ahead of schedule and approximately $1.8M under budget.


The Ballard Bridge (flanked by its approach structures) as seen from the east.

The Ballard Bridge carries 4 lanes of vehicular traffic, plus two sidewalks, over the Lake Washington Ship Canal between Interbay to the south and Ballard to the north. It is composed of three portions: a 295 foot long central portion and the north and south bridge approaches of 758 and 1801 feet respectively. The central portion (called a bascule) opens to allow ships taller than 44’ to pass between Puget Sound and Lake Washington on the Ship Canal.

Retrofit Project Overview

The Ballard Bridge Seismic Retrofit Project was part of Seattle’s city-wide program to upgrade its bridges. This project will prevent the Ballard Bridge approaches from catastrophic failure in a higher design level earthquake (with an expected 1,000-year return period) and will allow the bridge to remain fully operational following a lower design level earthquake (with a 100-year return period).

Nearly all work was done beneath the bridge and was not be visible from on top.

The seismic retrofit included the following types of work in strategic locations:

  • column jacketing
  • reinforced concrete seat extensions, restrainers, plinth retrofits, pier diaphragm bolsters and girder strengthening
  • replacement of longitudinal restrainers
  • addition of steel longitudinal blocking and steel deck joint restrainers
  • replacement of knee bracing with steel pier diaphragms.

Construction began in July of 2012 and finished in January of 2014. In general, work was classified as “on land”, “over water” and “in water”. The contractor completed all the “in-water” work (pier reinforcement and subsurface column jacketing”) by May 2013. The “on land” work (new steel diaphragms, concrete restrainers, longitudinal blocking, deck joint retrofits and seat extensions) took place under both the north and south approaches simultaneously through most of the project. The “over water” work activities were much the same as those on land, but were done primarily after the in water work was finished, from scaffolding erected on the contractor’s custom built barge.

Bridge History


Note the wooden timbers in the approach structure to the left.

In 1917 construction of the Ballard Bridge (designed by A.H. Dimock) was completed, with wooden bridge approach structures.

In 1939 the wooden bridge approaches were completely replaced with concrete and steel. A fascinating film made during that re-construction may be seen here.

In 1958 the north ramp was widened to provide access to and from Leary Way NW

In 1982, the bridge was placed on the U.S. National Register of Historic Places.

In 1989 the Loma Prieta earthquake struck San Francisco and in 1994 the Northridge earthquake struck Los Angeles.

In 1994 SDOT added seismic restrainers and replaced the steel deck grating on the bridge as part of a city-wide program.

In 2002 SDOT carried out an electro-mechanical rehabilitation to update the operating portion of the bridge.

In 2006 SDOT evaluated Seattle’s bridges, assessing their vulnerability to seismic events and the importance of these routes to Seattle area traffic. That evaluation resulted in a decision to seismically retrofit the approaches to the Ballard Bridge, as well as several other structures.

In 2009 the engineering firm of Berger ABAM began design work on the Ballard Bridge seismic retrofit and in 2012 the permitting for the project was concluded.

Project History

4/18/2012 – The Ballard Bridge Seismic Retrofit bids were opened, with the lowest of 9 bids accepted totaling $7,092,370 – almost 5% under the Engineer’s estimate.

5/8/2012 – The low bidder, Quigg Brothers Inc. of Aberdeen, WA, was recommended to receive the contract.

6/1/2012 – The contract with Quigg Brothers was executed.

7/30/2012 – The contractor began mobilizing on site.

9/11/2012 – The contractor began erecting scaffolding at the north abutment.

10/1/2012 – The contractor began in-water work.

4/1/2013 – The contractor finished all the in-water work; in one “fish window” rather than two.

8/20/2013 – The contractor essentially finished work on the north side of the Ship Canal.

2/24/2014  – The contractor essentially finished the work “over-water”  and on the south side of the Ship Canal.

3/14/2014 – The Final inspection is held.

Project Construction Impacts

A key design criterion for Ballard Bridge seismic retrofit project was to minimize impacts on traffic across the bridge; as a result most of the work was done from down below.

Vehicular lane closures were to have been limited as follows:

  • no southbound lane may be closed between 4:30AM and 10:00AM
  • no northbound lane may be closed between 3:00PM and 10:00PM
  • no two lanes be closed at the same time (except during full closures, covered below).

In addition, only one sidewalk or the other was to have been closed between 7:00PM and 6:00AM (but never both sides at the same time).

The project retrofit work was also allowed 3 full weekend long closures of the bridge to all vehicular traffic. (This was same number of full closures used during the replacement of the approaches on the Fremont Bridge in 2007). If needed these closures (on non-consecutive weekends) were to have been between 10PM on Friday and 6AM on Monday morning and would have been announced at least 2 weeks in advance.

As it turned out however, the seismic retrofit project never required a full closure of the bridge.
The Ship Canal Trail (which passes underneath the southern approach to the bridge) was to have been closed for up to 30 consecutive days at some point.  However, this too was avoided, by building a structure over the top of the trail under which bicyclists and pedestrians could safely cross.

The project created both noise and vibration, particularly so during the removal of certain structural elements. Normal work hours on this project were 6AM to 4PM Monday through Thursday, though work also took place on Fridays, at night or on weekends at times.

Environmental Considerations

SDOT conducted environmental reviews of the Ballard Bridge Seismic Retrofit Project to consider impacts associated with social/economic issues, biological resources, bicycles/pedestrians, historic/cultural resources, visual quality, land use, wetlands, and noise and vibration.

If you have any questions regarding the environmental permitting or associated protection measures on this project please contact: Mark Mazzola, SDOT Environmental Coordinator, at 206-733-9117 or mark.mazzola@seattle.gov.

Contemporary Projects

SDOT’s staff worked to minimize impacts of the Ballard Bridge Seismic Retrofit project by coordinating activities with other projects in the area:

Project Budget & Funding

The total estimated project cost is $15.5M, which includes engineering, geotechnical work, structural design, permitting, and right of way management in addition to the construction.

The project is funded by Bridging the Gap, a nine-year levy for transportation maintenance and improvements. The $365 million levy was passed by Seattle voters in November 2006. The goal of the program is to create a strong foundation for Seattle’s transportation future by reducing the infrastructure backlog and investing in major transportation projects.

 

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