Wx and the City
As CWG's Ian Livingston noted last week, the D.C. Department of Transportation began on March 11 a month-long crusade to fill the city's potholes. Deemed "Potholepalooza," the initiative aims to have all reported potholes filled within 48 hours (typical turnaround is 72 hours). Based on some of my bike rides lately, our streets sure need the help.
Why do these potholes form? The answer has to do with the physical properties of water -- including the fact that, unlike many other liquids that contract when they freeze, water expands -- and the fluctuating temperatures of early spring.
Keep reading for more on potholes and an update on D.C.'s efforts to fill them.
The hydrogen atoms between water molecules (each water molecule contains two hydrogen atoms and one oxygen atom) like to link together by forming hydrogen bonds. In liquid water, these bonds are fairly weak and can break and form again and again (here's a video of liquid water in action). However, as the temperature decreases, water molecules slow down, stay bonded together and, if cold enough, eventually freeze into a very unique and stable lattice structure.
March is a great time to form if you're a pothole. Rain and snowmelt seep through cracks in a street and collect in the soil below. Freezing temperatures cause the water to turn into ice, which expands, pushing the pavement up. When temperatures rise again, the ice melts, the liquid water evaporates or seeps into the ground, and a hole is left underneath the pavement. When a vehicle drives over this weak spot, the pavement cracks and drops into the hollow below and voila: a pothole -- not to be confused with a sinkhole or utility cut -- forms. Check out this graphic to see the entire process.
How is Potholepalooza doing so far at filling in these pesky potholes? Within just the first week, over 1,200 potholes have been filled -- 518 on Monday alone. If the weather is just too boring for you this week, you can monitor the city's daily pothole-filling progress at DDOT.
If you happen to hit a pothole with your car and you notice steering problems, low tire pressure, or visible bulges or blisters on your tires, it is a good idea to have a professional check your vehicle for damage and make any necessary repairs. And if you're a cyclist, be especially cautious in avoiding potholes.
Even though potholes are a nuisance this time of year, just be thankful we don't experience frost heaves in D.C....
See Ann Posegate's previous Wx and the City posts.