Not an unreasonable question: “Why aren’t there more storm cellars in Oklahoma?” Megan Garber explains to Atlantic readers something I’ve explained before in less detail:
The ground in central Oklahoma tends to be soft and moist — right down to the bedrock that sits, generally, some 20 to 100 feet below the surface.
Here’s the problem with that when it comes to building basements and underground shelters: Clay is particularly fickle as a foundation for construction. When loamy soils absorb rainwater, they expand. And when the weather’s dry, they contract. This inevitable and yet largely unpredictable variability makes basement-building a particular challenge, since it makes it nearly impossible to establish firm foundations for underground construction.
And while above-ground homes can be built on these somewhat shaky foundations, adding the element of open space in the form of a basement is a nearly impossible feat of engineering. There is a chance your house, its basement surrounded by glorified mud, will eventually simply topple into itself.
One of the houses I looked at before buying this one was about to slide off a hill, possibly for exactly that reason. Same price as mine, for half again the space — for a while, anyway.
But why not…? This is why not:
To mitigate this, contractors have been experimenting with steel reinforcements for basements, bolstering underground walls with steel beams that are drilled directly into the bedrock below. The problem here, though, is that much of Oklahoma’s bedrock is composed of limestone, which, just like the soil above it, absorbs water. And which, when it’s sapped of moisture, becomes chalky.
About the only thing Garber gets wrong in the whole article, in fact, is her placement of Moore in Oklahoma County. It is, of course, in Cleveland County, as is the section of Oklahoma City that was hit before the storm reached Moore.