Friday, February 10, 2017

Why do we close the Hood Canal Bridge during powerful weather?

By Doug Adamson

When you drive cross the Hood Canal Bridge, we want you to do so with the confidence that knowledgeable and skilled crews are ensuring the bridge is safe and operational. When inclement weather hits western Washington, we pay particular attention to our floating bridges. The SR 104 Hood Canal Bridge is unlike our other floating bridges like I-90 and SR 520 in Seattle because they cross a lake and are not subject to tidal forces. Not only is the Hood Canal Bridge subject to the daily stresses of tidal swings, but in bad weather fierce winds and wind directions intensify those water forces being exerted on the bridge. The pressure is strong enough that it could damage key components of the bridge, especially in the center of the bridge where the bridge's movable parts operate the drawspan.

This video shot from the Hood Canal Bridge control tower shows the violent shaking that occurred during a powerful windstorm. Notice that once the drawspan opened, the shaking stopped as it relieved pressure on the bridge.

When do we close the Hood Canal Bridge?
We watch winds closely at the Hood Canal Bridge and use automated systems to inform us when wind speeds are on the upswing. When winds reach or exceed 40 mph for 15 minutes or longer, our crews consider closing the bridge to traffic and opening the drawspan to relieve pressure on the bridge. Strong tides, wind directions and driver behavior also play a role in their decision. If drivers of high-profile vehicles like semis and box trucks are being buffeted by wind and waves, it's time to consider closing the bridge. We never take that decision lightly, as we are very aware of how critical the Hood Canal Bridge is to businesses, residents and communities, but we believe public safety must come first.

Crews monitoring weather
We have key equipment that monitors wind conditions of the bridge. Our crews see real-time wind speed, peak gusts, and direction. When winds pick up, they monitor conditions closely from the control tower and stand ready to respond.

Why can't you tell me when the bridge will reopen?
While we regularly check weather forecasts, it is extremely difficult to pinpoint when the weather will calm down. The decision on when to reopen the bridge to traffic is based on real-time conditions. We need to make sure the severe weather is behind us or we face the possibility of damage to the structure. During high winds, it also can be very difficult to close the drawspan. Since both ends are being pushed by wind and tides, it could be compared to trying to thread a needle while your hands are shaking.

"But the wind is not that bad!"
We often hear that comment from frustrated drivers waiting for the bridge to reopen. While that may be the case on shore, it may not be the case on the bridge. Topography is key. Areas of the shore can be sheltered, but the Hood Canal Bridge has no windbreaks. Consider the force of winds and waves on that expansive open water.

We want to emphasize that we understand the importance of the Hood Canal Bridge. It is the only span between the Kitsap and Olympic Peninsulas. We also understand that the alternative is to drive a long way around the canal via Mason County. Our job is to help people move about our state. That allows people to get to their girls basketball game, get home from work, or do business. We want you to be able to get where you are going. At the same time, we need to protect this vital link.

Driver Resources
Drivers can receive up-to-date Hood Canal Bridge information through several resources. Advance notification does not occur for passage of marine vessels associated with the Department of Defense.
  • Social media users can follow updates on Twitter
  • WSDOT Hood Canal Bridge web page
  • WSDOT email and text updates
  • Hood Canal text messages:
    • Send a text message to 468311 with the words "wsdot hood"


Unknown said...

Hello Doug, so how do we begin the process into other options such as a suspension bridge so the Peninsula is not shut down if there is a problem with the bridge and 106 or 101 is also closed?

Kris Springer said...

I want to thank WSDOT for its sensible attitude. The 1979 sinking of the bridge probably helped with that attitude. I have only been on the O.P. for a year and a half, so I am not familiar with very many other closings of this floating bridge due to weather. Living in Port Ludlow, I do use the text app and have found it quite useful. Wondering how prohibitive to population growth on this side of the Sound is attributed to the floating bridge and the Port Townsend Ferry as the only "quick" ways to the other side. I am retired and quite prefer the slower life.

WSDOT said...

We previously looked into whether an elevated structure, such as a suspension bridge, would work for Hood Canal. We found such as bridge at this location would be very costly. The canal at the bridge is more than 300 ft. deep. There also is a great distance between each side. A concrete floating bridge provides a cost-effective solution for crossing a channel with very deep and soft soils in this area.

Pete Murney said...

Good job WSDOT on the video! I think you are using the text alerts excellent way to cascade information to a large group who depend on the bridge. I live in Port Townsend and we drive to Poulsbo regularly.

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