A winter and spring of heavy rains plus freeze-thaw cycles is hard on the roadways and leads to the development of potholes: broken places in the pavement. The Seattle Department of Transportation (SDOT) has a page dedicated to the cause, reporting and cure of potholes.
Why are there so many potholes in Seattle streets?
You can expect to see more potholes in the winter and spring, following periods of cold temperatures and rain or snow. Many streets, particularly in the outer areas of the city have a very poor underlying structure, or sub base, which reacts poorly to these conditions. The asphalt heaves upward as the water under the road and in small cracks freezes and expands.
It is helpful for the public to call SDOT and report potholes on streets within the city limits, via 684-ROAD (7623), so the potholes can be filled quickly.
SDOT filled a pothole, but a few days later, there it was again. Why don’t the repairs last longer?
The material used to patch potholes doesn’t stick as well to the surrounding pavement when it is cold or wet, so repairs made in the winter may not last as long as on dry, warm pavement. Pothole repairs made under adverse conditions may not last as long, but the potholes still need to be filled for reasons of safety.
If the cause of the pothole is not corrected, such as water getting under the pavement, pothole patches may fail, or more potholes will continue to form. The long-term solution is to repave the street, and in some cases, to reconstruct the street from the ground up, and from curb to curb. Potholes are also temporary repairs. That said, some pothole repairs last longer than others.