I grew up, as many did, with the tornado in the Wizard of Oz seared into memory. As a child, I came to understand that on the aproach of a tornado, you ran inside a storm cellar, a hole in the ground dug out for the specific purpose of protection from the wind. It is natural, then, that many of us watching the tornado devastation in Moore this week wondered why more homes and the schools did not have storm cellars. The
New York Times looks into this:
The Web site for the City of Moore, Okla., recommends “that every residence have a storm safe room or an underground cellar.” It says below-ground shelters are the best protection against tornadoes.
But no local ordinance or building code requires such shelters, either in houses, schools or businesses, and only about 10 percent of homes in Moore have them.
Nor does the rest of Oklahoma, one of the states in the storm belt called Tornado Alley, require them — despite the annual onslaught of deadly and destructive twisters like the one on Monday, which killed at least 24 people, injured hundreds and eliminated entire neighborhoods.
The lack of basements can be explained by the geology of Oklahoma and other tornado alley states, as Megan Garber explains.
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 (pdf),
"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.
But this explains why structures don't have full basements, not the 21st century version of the Gale family storm cellar. Nor does it explain the absence of community shelters or shelters in schools. The
NY Times takes this on.
In Moore, the Web site explains that the city has no community shelter because a 15-minute warning is not enough time to get to safety and because, “overall, people face less risk by taking shelter in a reasonably well-constructed residence.”
This is generally true, but not for a storm like Monday’s milewide tornado, which was a terrible reminder of a tornado that caused extensive damage on May 3, 1999.
Curtis McCarty, a member of the Oklahoma Uniform Building Code Commission and a builder himself, said the twister on Monday would have defeated attempts to resist it above ground. “You cannot build a structure that’s going to take a direct hit from a tornado like that that’s going to stand,” he said.
...................
Construction standards in Moore have been studied extensively. In a 2002 study published in the journal of the American Meteorological Society, Timothy P. Marshal, an engineer in Dallas, suggested that “the quality of new home construction generally was no better than homes built prior to the tornado” in 1999.
Few homes built in the town after the storm were secured to their foundations with bolted plates, which greatly increase resistance to storms; instead, most were secured with the same kinds of nails and pins that failed in 1999. Just 6 of 40 new homes had closet-size safe rooms.
Mayor Glenn Lewis of Moore said that since then, the town had strengthened building codes, including a requirement that new homes incorporate hurricane braces. The city has also aggressively promoted the construction of safe rooms and other measures, with more than $12 million from state and federal emergency management funds to subsidize safe-room construction by offering a $2,000 rebate, said Albert Ashwood, the director of the Oklahoma Department of Emergency Management. Still, he said, it has been several years since Moore has received new financing for the program.
......................
Mike Gilles, a former president of the Oklahoma State Home Builders Association, said that he built safe rooms in all his custom homes, and that even many builders who build speculatively now make them standard.
But asked whether the government should require safe rooms in homes, he said, “Most homebuilders would be against that because we think the market ought to drive what people are putting in the houses, not the government.”
Mr. Anselm, the official in Joplin, said that the city had applied to Missouri for emergency funds for safe rooms, but that the state used money from the Federal Emergency Management Agency primarily for disaster relief from flooding. [my bolding]
Lack of money, diversion of public funds, building code resistance, learned helplessness and magical thinking: besides geology, these explain the absence of storm shelters.
