Contractor crews will replace 28 steel anchor cables on the Interstate 90 floating bridges on Lake Washington, between Seattle and Mercer Island. The cables stabilize the bridges and help keep them in place.
Why is WSDOT
replacing anchor cables on the I-90 floating bridges?
The cables must be replaced every 25 to 30 years to maintain the safety and integrity of the bridges. The cables are subjected to years of pressure and stress from wind, waves, currents and changing traffic loads. Over time, the cables corrode, rust and fray.
Each cable is 2-3/8 inches in diameter and made up of dozens of steel wires wrapped around each other. One end is hooked to an anchor, or large concrete structure on the lake floor. The other end is fed into a floating pontoon where it is tightly secured and tensioned.
There are a total of 108 cables on the I-90 floating bridges:
- 56 on the eastbound Lacey V. Murrow Memorial Bridge
- 52 on the westbound Homer M. Hadley Memorial Bridge, including the express lanes and pedestrian/bicycle trail
Most of the 28 cables being replaced in this project were installed between 1983 and 1991. They range in length from 335 to 745 feet. Laid end to end, 15,630 feet of cable will be replaced, or just shy of three miles.
How will the work be done?
For each anchor cable being replaced, a specially trained commercial deep sea diver must descend and locate its anchor embedded in the lake floor. Using an underwater cutting torch, the diver will disconnect the cable attached to the anchor. The cable will be winched to the surface and spooled.
Another diver will descend to the bottom of the lake with a new cable and securely attach it to the anchor. The other end of the cable will be fed into a pontoon, then tightened and secured. This process will be repeated until all 28 cables are replaced.
To learn more about anchor cables replacement work, watch our videos from a similar project completed in 2015.
The End Result
Replacing anchor cables on a regular basis preserves the structural integrity of the bridges, stabilizes the bridges during storms and ensures the safety of the 132,000 commuters and freight traffic who use I-90 to cross Lake Washington each day.
- Preservation: This work helps preserve and extend the lifespan and stability of I-90, which is one of only two routes across Lake Washington.
- Traffic: Worn cables pose a higher risk of snapping during a windstorm, which could lead to a long-term closure of the bridges, disrupting traffic for the thousands of drivers who use the bridges every day.
- Economic: Replacing cables on a regular basis ensures that the bridges remain open. It is an important link to the Port of Seattle, downtown business areas and the Interstate 5 corridor. An unexpected closure of the floating bridges due to cable damage or failure will disrupt the Puget Sound economy as commuters and freight are delayed reaching their destinations.
What is the project timeline?
- August 2017: Project is scheduled to be advertised for competitive bidding.
- Spring 2017: Construction is scheduled to begin.
- Fall 2018: Construction is scheduled to be complete.
|Financial Data for PIN 109024M, 109024N
||Amount ($ in thousands)
|2003 Gas Tax (Nickel Funding)
|2005 Gas Tax (TPA)
|Pre-Existing Funds (PEF)
The total estimated cost for this project is $5.8 million.
How can I get more information?
back to top