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Since You Asked: Water is the enemy

With the recent snow and rains we've had this winter, it seems like the potholes are a lot worse this year, particularly along Highway 99 near Rogue River. What causes them to be so bad after the winter?

— Chris S., Grants Pass

Those aren't potholes, Chris. They are rubble-ized pavement events.

Seriously, since we obviously know very little about potholes except how they have destroyed the suspension on the Since You Asked company bus (dubbed "Furthest"), we took your query to the officials of the Oregon Department of Transportation, not to say they have a lock on the region's potholes.

Here's what Gary Leaming, ODOT project information specialist, had to say: "Water is the enemy."

OK, he said a little bit more: "Water is the enemy of pavement, plain and simple."

Moisture, either through rain or snow, finds its way into the cracks in asphalt or concrete. In the winter, the intruding water goes through the freeze-and-thaw process. When moisture freezes, it expands, thus causing the road surface and the rock base underneath to loosen. If you multiply that degenerative action many times during the year, you can see why roads begin to have problems, Leaming said.

Then we add to the damage with vehicle traffic. When traffic drives over water-compromised pavement, the weight compresses the moisture into any layer it can find. The resulting hydraulic pressure pushes the water to the easiest exit, which is through any nearby crack — "thus creating the potholes we have come to love to hate," Leaming said.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to youasked@mailtribune.com.