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LOCATION: Northeast 21st Avenue between Sandy Boulevard and Flanders Street
SUBMITTED BY: Michelle Mehr
HOW SHE FOUND IT: Sorry, but we must digress. Before we get to this week’s hole, we’d like to go back to the books and discuss the difference between a pothole and sinkhole. A number of readers (and one city spokesperson) have written in to educate us on this point, so we’re going to share what we’ve learned. (Apologies to Dr. Know for stealing his bit.)
A pothole is a depression in the asphalt formed when rain soaks into the roadway and freezes. Water is one of the very few magical molecules that expands as it cools. Take a look at your ice cube trays if you don’t believe us. Or ask yourself why icebergs float.
This quirk of our universe is a problem for cities in wet, temperate climates, like Portland, where rain seeps into asphalt during warmer storms, then malingers there until a deep freeze. The water expands, cracking the surface of the road, which lets in more water, which freezes again…and so on. Run thousands of cars over the weakened blacktop, and you get a pothole.
Sinkholes are different. They start from the bottom. Rock or soil under the pavement collapses or is washed away by an underground water source, and the asphalt crumbles into the void.
The Portland Bureau of Transportation contacted us about the hole on Southeast 28th Place, between Cora and Holgate streets, that we wrote about last week. We called it a pothole, but a PBOT crew came out and poured (harmless) dye into it. Colored water came out of a maintenance hole nearby. That means there is a sewer leak or stormwater break that compromised layers of material below the asphalt.
“Crews installed a steel plate over the sinkhole for safety and will be excavating and making repairs around April 10,” PBOT spokeswoman Hannah Schafer wrote in her email.
Now, about this week’s hole: It’s not on a main drag. Twenty-First Avenue is sleepy in this section, which might appeal to bikers looking to avoid bustling 20th. But hit this gaping maw on anything short of a full-suspension downhill mountain bike and you’re likely to get bounced.
CURRENT STATUS: Collecting rainwater.
This pothole now advances to the Hole Patrol Winner’s Bracket. Each week through the end of April, WW will select another reader-submitted pothole to move into the Winner’s Bracket, where it will be evaluated by our crack team of asphalt researchers using a proprietary methodology (we’ll probably measure it). The person who submits the city’s biggest pothole will receive a splendid prize. Send your entries to newstips@wweek.com.