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Cooling down hot moving bridges

Dawn breaking on the Ballard Bridge | Photo by David Johnson

What do you do when the city experiences three consecutive days of 85+-degree weather?

A. Drink a lot of water

B. Cool off your britches with a pool dunk

C. Cool off moving bridges with a water flush

D. All of the above


Admittedly, any of these answers is right – though our Roadway Structures bridge crews focus on “C”. That’s because temperature changes cause steel and concrete to expand and contract, a potential problem for bridges that open and close for passage of marine vessels. Too much expansion can create pinch points, where bridge sections can rub – and therein lies the rub, and reason for the flushing.


With this week’s high temps, the cooling truck (like a calming goat, only different) was out Thursday, at all three Ship Canal bridges – University, Ballard, and Fremont – consecutively. The water flushing operations are scheduled when Seattle experiences 2 – 3 consecutive days of at least 85-degree heat. Lucky for us, it didn’t get as hot as THIS looks…

2011 Google Earth Visual | Discover Magazine |

Thanks to everyone for your patience during those 5-10-minute bridge closures! If temps creep up again, expect to see moving bridge gates down, just briefly, for that cooling/flushing truck and our team to work some misty magic!

SDOT Roadway Structures crews using the bridge cooling truck.