That title is not hyperbole — we have some weapons-grade potholes going this week. This is my 28th winter in East Central Iowa, and I do not recall a time when the streets were worse than this. There were two holes at the end of my street that were big enough to hold a basketball. (These were cold-patched yesterday, but see below.)
A lot of people here have been complaining about how poorly our streets are maintained, and it’s somewhat warranted. A lot of priorities changed after the epic flood in 2008, and some street repairs were put off because crews were busy with other things. But it’s not fair to complain about the government or the crews on this. Sure, the poor condition of some streets made this worse, but it’s primarily because we’ve had such a deeply cold winter.
Nearly everything shrinks as it solidifies. In fact, there are three exceptions. Bismuth and antimony both expand as they solidify. This is why they are used in type-metals — they don’t shrink and pull away from the corners of the mold. Clearly, though, these are not the issue — you won’t find these out on the streets in any quantity that matters. (I’m guessing you won’t find much of them anywhere at all.)
The third exception is water — good, old-fashioned H2O! This expansion is why you can’t just put a soda in the freezer and leave it. The water will expand and crack the can. Unfortunately, it does the same to the streets. Here’s the general process:
- We live in a somewhat less than ideal world. As temperatures change (not just from season to season, but sometimes overnight), roads and sidewalks expand and contract. This causes cracks to form. It can’t be helped. There are materials that resist this better, but they’ll all crack eventually.
- When water fills the crack (for any reason: rain, melting snow, garden hoses), and then it freezes, the expansion pushed the crack wider and makes it worse. Not a lot worse, but the process then repeats with the larger crack. Every melt/freeze cycle makes the crack a little wider, longer, or both.
- In addition, normal traffic then stresses the cracks, causing damage and creating potholes.
This happens anywhere you get freezing temperatures when things are wet, not just in wintry climes. Mind you, roads are damaged just from the expansion and contraction and normal traffic wear — but freezing is why it’s usually worse after winter.
But that’s not the only factor. Winter here has been colder than normal, and for a longer time, and that’s caused frost heaving. The same mechanism is involved, but in a different way.
Frost heaves happen when ice forms in the soil. The frostline in this part of Iowa is about four feet down, but this year we got to six feet (or more, in places). This means we had freezing temperatures in the soil at or below the level of the water table, so that water starts to freeze. As it does so, it expands, moving up toward the colder temperatures (in a lens shape). Water from the table fills in behind, and the process repeats until a bubble forms on the surface. If this is under a street, it causes the street to push up and buckle. Think of it as a large “anti-pothole.” Hitting it isn’t any better than running your tire into a big hole.
Unfortunately, frost heaves are very susceptible to being hit by plows. Both the plows and the streets are damaged (sometimes quite badly), and things go very bad very fast. They also affect basements, pilings, driveways…and I’m seeing some of that here at the house. The driveway has started to buckle, and it’s possible that my basement or the pilings for the deck may be damaged.
Oddly enough, as cold as it is here, January was the fourth-warmest on record, globally. My boots may be frozen to the pavement, but other parts of the world are experiencing huge heat waves. Alaska is so balmy that animals are out of hibernation early (and starving because there is no winter-kill, making things dangerous). Australia is having a record heat wave. So the global average temperature is high.
In short…the weather sucks this year, EXACTLY WHERE YOU ARE! Good luck!