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A Killer F5 Tornado Rips Through Dallas County -- How Ready Are We for this Nightmare Scenario?

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Educated as a meteorologist and engineer, he has made his living as an expert on storm damage, and he likes to be on location when nature's hammer comes down. "I testify in civil litigation, and it's useful for people to know I was there. Lawyers love the fact that I ride out hurricanes on the Gulf. I'm not just some landlocked engineer from Dallas, Texas," the 52-year-old Marshall explains. "I've seen tens of thousands of homes destroyed in my lifespan. You see the same failures over and over again. They occur routinely."

In tornado-struck areas in Texas and Oklahoma, he has seen a surprising number of single-family homes that were not properly constructed and fail to meet building codes that typically require them to withstand straight-line 90 mph winds. A big strike in the Dallas area would no doubt confirm the extent of the problem, he says.

"Anchors. Braces. Connectors. Those are the three things that are so important that so often I see done wrong," he maintains. "Code says you have to anchor the house to the foundation with bolts every 6 feet. You'll find them without a nut and washer on the bolt, or just a washer, or they skip the bolts all together and use cut nails."

In Arlington, in the two subdivisions that sustained F2 damage in the March 2000 tornado strike that also sent a twister into downtown Fort Worth, Marshall found houses where brick walls weren't anchored to the house frame. "Four out of five houses I looked at had some sort of fatal flaw," he says. Houses with attached garages, the prevailing suburban style, are inherently vulnerable. "You have a door panel, 7-by-16 foot that blows in easily, leaving wind inside your garage. That internal pressure helps pop off the roof from below. I see numerous cases where there was increased damage to houses that had an attached two-car garage."

He adds, "The Three Little Pigs did us a great disservice." Brick houses, or rather frame homes with brick veneer, are easily punctured by tornado debris missiles. And in many cases, he finds houses where the brick was not properly tied to the frame, so the brick walls simply fall down. The nursery rhyme, Marshall says, should have had another verse about steel-reinforced concrete—materials that make interior spaces in high rises one of the better places to weather a violent tornado.

Marshall says he is accustomed to taking heat for his views, which become relevant during insurance disputes and court cases with large damage awards at stake. Over the years, he has been knocked as both a shill for insurance companies—for suggesting that water did most of the damage along the Gulf Coast in Hurricane Katrina—and an enemy of the free market. The later was pinned on him when he advocated requiring mobile home parks in Kansas to provide residents with tornado shelters. The mobile home lobby knocked the idea flat, he says.

For a house hit by an F5 tornado working at full force, even well-fastened anchor bolts wouldn't make a difference. But almost all tornado damage occurs at lesser wind speeds, Marshall says.

Experts spent considerable time debating the strength of the May 27, 1997, tornado that swept through Jarrell, north of Austin, and killed 27 people. Storm-damage photos showing clean-swept foundations where 40 single-family homes once stood lent support to the National Weather Service's official finding that the tornado reached F5 intensity.

But in a report the following year, a team from the federal Building and Fire Research Laboratory concluded that the twister was a tamer F3. Homes in the subdivision, which was located on county land and not regulated by building codes, were poorly constructed, fastened down with nails and likely were knocked down and carried away by lesser winds, the report found.

Government safety warnings, developed from experiences in past tornadoes, instruct people to take shelter in a central, ground-floor room of their house rather than attempt to flee. The risks of taking flight on the roads were borne out in the April 10, 1979, Wichita Falls tornado. Twenty seven of the 42 people killed were attempting to escape the mile-wide wedge funnel in their vehicles.

Advice to stay put worked poorly in Jarrell, but extensive reviews of the Oklahoma F5 suggest it served people well there. Emergency officials in Moore estimate that 2,000 people were in the twister's path and took shelter, like the Bernich family, by huddling low in their house's or apartment's interior rooms. Just three were killed, an outcome federal officials describe as remarkable given the tornado's intensity.

Photos and video footage of the damage show trees stripped to their trunks and houses reduced to lumber piles. But a closer look shows many homes survived with a few interior walls standing—just enough space to furnish shelter. "We found that the majority of people who sought shelter inside their homes survived the tornado without serious injury," says Marshall, who worked with a Texas Tech team surveying the damage. In a report on its findings published in 2002 in the journal "Weather and Forecasting," Marshall wrote that in developed areas, tornado damage begets more tornado damage. "As homes broke apart, their debris impacted neighboring homes, compromising them as well."

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Thomas Korosec
Contact: Thomas Korosec