King County Road Services - Capital Improvement Program
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South Park Bridge #3179 - Replacement Project
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Project No.:
300197
Project limits:
14th/16th Ave S. over Duwamish River
Current phase: Construction start
Project type:
Bridge
Thomas Bros. Map No.:
625b3
Project description
Construct a new moveable bridge over Duwamish Waterway parallel to and downriver of the existing bridge. The bridge replacement project will also realign the intersection of 14th Avenue South and Dallas Avenue South/South Sullivan Street, construct natural water treatment systems such as a rain garden, build roadway and drainage facilities, relocate conflicting utilities, restore riverbanks by creating gentle slopes for tidally influenced areas and planting riparian vegetation.
Why is King County doing this project?
The existing bridge was built in 1929-1931 and closed on June 30, 2010 due to its severe deterioration and vulnerability to earthquakes. The original foundation piles were not driven deep enough, making the bridge susceptible to settlement and resulting in the tilting and cracking of the main piers. The mechanical and electrical systems that operated the bridge were unreliable and required repairs frequently. With lanes narrower than standard, the bridge carried up to 20,000 vehicles daily with 14% being truck traffic.
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| Status as of
May 21, 2013 |
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Both in-water bascule piers walls are under construction. Decks on two of the four approach spans are complete. All nine girders of the third approach span (span 2) connecting the land-based pier to the in-water pier on the south side were set on April 15-16, 2013. Both abutments are constructed. Reconfiguration of 14th Avenue South, Dallas Avenue South, South Sullivan Street and South Sullivan Place is complete. Both bascule spans and trunnion frames are assembled and painting of these structures is underway at nearby site. Machinery and electrical fabrication is nearly complete. Drainage systems are in place. Demolition of the south half of old bridge is nearly complete. Construction of the rain garden is under way. Utility tunnel between main in-water bascule piers is complete. Pedestrian rails are almost fully fabricated.
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Environmental informationThe South Park Bridge spans the navigable channel of the Duwamish Waterway, which is used for industrial, commercial, and recreational purposes. The natural habitat in the project area has been extensively altered through human activity. Urban landscapes in the form of landscaped backyards, parks, street trees, and undeveloped steep slopes are the primary terrestrial habitats in the vicinity of the project area.
To reduce environmental impacts during project construction, certain in-water work must be completed during a 6 1/2 month work window between August 1 and February 15th annually. Some of this work involves removing about 352 creosote-treated piles that serve as pier protection for the existing bridge. They will be removed/cut off and replaced with steel piles, thus improving water quality. Removal of the existing approach bridge piers will remove 671 square feet of structure from intertidal areas of the Duwamish River used by migrating salmonids.
The project-wide mitigation plan will include shoreline enhancement, including removal of bank armoring, creation of new intertidal zone, and riparian planting, which will partially offset affected functions and values within the Duwamish Basin, and water quality treatment for impervious surfaces.
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See also
Environmental compliance for bridge activities
King County Annual Bridge Report
Overlegal truck permit
Road closures
Road standards
Seattle bridges
Title VI information
WSDOT Historic Bridges
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How does the CIP work?
The Road Services Division Capital Improvement Program (CIP) contains all design and construction and studies for improvements on roads, bridges or transportation facilities in the unincorporated areas of King County. We have a glossary to help explain our terms and jargon.
Information from the Road Services Division's Web site is available to people with disabilities in alternate formats upon request by calling 206-263-6482 or 711 for the TTY relay service.
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