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In response to
"I think you mentioned that in OK, not so many people have storm cellars. why is that? -- nm"
by
loosi at home
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"The relative dearth of storm cellars in Oklahoma may be partially attributed, as things so often can, to environmental factors."
Posted by
JaxSean (aka JaxSean)
May 21 '13, 18:25
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Ground That's Made of Clay
The relative dearth of storm cellars in Oklahoma may be partially attributed, as things so often can, to environmental factors. The soil in the state is composed largely of clay -- and that's particularly true in central Oklahoma, where Moore is located. ("Soils in the Central Rolling Red Prairies," geologists at Oklahoma State put it, "are dark and loamy with clayey to loamy subsoils developed on Permian shales, mudstones, sandstones and/or alluvial deposits under tall grasses.")
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.
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 (pdf), which, just like the soil above it, absorbs water. And which, when it's sapped of moisture, becomes chalky.
So, you can try to enforce your basement with steel; ultimately, though, the steel will be anchored to rock that is "rock" only in the broadest sense of the word.
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