Bridges

What we do

Some of Seattle's bridges make connections over bodies of water, like the West Seattle Bridge. Other bridges, like the Magnolia Bridge, are viaducts that make connections over valleys. Some bridges, like the Fremont Bridge, serve all travel modes and others are limited to foot or bike traffic, like the W Thomas St Overpass.

SDOT owns, inspects, maintains, and/or operates nearly 280 bridges. Bridge program work includes:

• Bridge Painting Program: Painting steel and other metal on bridges protects them from corrosion and rust. The typical life of bridge paint is 18 years.
• Bridge Load Rating Program: Managing the safe weight capacity of bridges is an important element to bridge safety. Activities include analysis of the weight capacity of bridges, field verification tests, and monitoring of instrumentation on deficient bridges.
• Capital Improvement Program: Some bridges require major  rehabilitationor replacement to ensure they remain safe and available to the traveling public. Capital projects often involve a multi-year planning, design, and engineering process.

This Capital Projects and Roadway Structures 2018 Annual Report provides information about SDOT's key structural assets: bridges, retaining wall, stairways and areaways.  Combined, these assets represent over $8.3 billion in replacement value. The report also highlights capital improvement projects that were completed or underway in 2018. 

Bridge openings

In the city, there are7 vehicular moveable bridges over navigable water, of which 4 are owned by SDOT. Federal law requires bridges open for marine traffic, with few exceptions. Seattle is part of the US Coast Guard 13th District. More information is available at www.uscg.mil/d13/.

Seattle's moveable bridges

Here is a list of vehicular bridges in Seattle that open for marine traffic.

Bridge opening schedule

Bridges open on request between 7 AM and 11 PM. From 11 PM to 7 AM, bridges open by appointment only. The average bridge opening, from the time street traffic stops to the time it resumes, lasts about 4 minutes. The Spokane St Swing Bridge openings last about 10 minutes.

Seattle's Ship Canal Bridges - University, Fremont, and Ballard Bridges - have restrictions in place during the morning and afternoon peak commute to help keep street traffic moving during busy hours. These 3 bridges stay closed to marine traffic on weekdays, from 7-9 AM and from 4-6 PM, except for federal holidays but Columbus Day and for any vessel of 1,000 gross tons or over. See the federal regulation for Lake Washington Ship Canal bridges here. Information on Montlake Bridge openings is available here.

How to request a bridge opening

· Between 7 AM and 11 PM, vessels should contact the bridge by radio (Marine Channel 13 or call (206) 386-4251) or use a whistle signal: one long, one short.

· The US Coast Guard requests pleasure vessel use a whistle signal from 7 AM to dusk.

· Between 11 PM and 7 AM, bridge openings are by appointment only, and should be requested no less than 1 hour prior to the opening.

· For openings by appointment, the bridge operator will wait 15 minutes after the appointment time before contacting the vessel on Marine Channel 13. If the bridge operator doesn't receive a response, the operator will leave for the next appointment. · For state- or county-owned bridges, visit www.kingcounty.gov/ or www.wsdot.wa.gov.

Bridge Seismic Retrofit Program  

Safety for the traveling public is our number one priority. Every bridge is built to the earthquake standards of the time it is designed and receives ongoing maintenance. The bridge seismic retrofit program is one type of investment which goes above and beyond basic maintenance to bring sturdy but older bridges up to modern standards. The program is implemented in tandem with the basic bridge maintenance, regular inspections, monitoring, preservation, and repairs we perform continually to keep bridges safe.

We worked with industry subject matter experts to develop our Bridge Seismic Retrofit Program in 1990 and have since continued to work with experts to update and revise our Bridge Seismic Retrofit Philosophy, Policies, and Criteria. We are currently working on the latest revision of this document. In phase one of the program (1990-2005), we completed seismic retrofits on 23 bridges. In phase two (2006-2015 - thanks to the voter-approved Bridging the Gap Levy), we completed seismic retrofits on 7 bridges. 

We are currently in phase three of the program which is fully funded through the voter-approved Levy to Move Seattle.  

At the beginning of the Levy to Move Seattle, we estimated 16 new seismic retrofits could be completed based on the costs and level of effort to implement seismic improvements in phase one and two. It was always understood we would need to perform more complex modeling, inspection, and analysis to determine the specific improvements needed for each bridge listed in the Levy to Move Seattle. Similar to when one is preparing for home repairs, cost estimates often change when you take a deeper look and consider current codes. This happened when we did analysis for phase three of the Seismic Retrofit Program and higher costs were revealed. The change was because 1) estimates were based on older bridge projects which were completed first because they had simpler needs, and 2) engineering best practices have advanced in recent years and newer modeling assumptions help us to better understand how the soil around bridges would react to a large earthquake. The analysis led us to realize 5 of the bridges required much more complex investments to achieve current earthquake safety standards.

Knowing what we do now, we are focusing on the 11 bridges where analysis confirmed the investment makes sense. We are still committed to taking care of the other 5 bridges, and our plan is to conduct future evaluation to determine the best type of investment for each bridge (such as extensive seismic retrofits in a future phase of the program, or other kinds of rehabilitation or full replacement if that makes more sense). The planning going on now, sets us up for possible grant and new funding opportunities as they become available. 

Vehicle weight restrictions on bridges