May 31, 2013, 6:08 AM — If the question about tornadoes comes up at his Oklahoma City data center, as it sometimes does, Todd Currie, vice president of operations and general manager at Perimeter Technology, has answers. He even has cutout sample of his roof to show how it is built.
Perimeter's data center was constructed to withstand an EF3 tornado, or winds up to 165 miles per hour on the Enhanced Fujita scale.
To protect against an EF3, Perimeter surrounded the raised floor portion of the data center with 8.5" concrete, reinforced walls. The data center is in the middle of the building, and around it are offices protected by another 8.5" exterior wall.
"It's kind of like of a box within a box," Currie said of the design. They also have data centers in Washington State, Texas and another in Tulsa, two move operations if need be.
The roof is double reinforced and thick enough to withstand the storm's uplift. But the thicker roof also pays dividends in insulating the building and that's helps with cooling, said Currie.
Currie is more likely to get a question about tornadoes from out-of-state customers, people unfamiliar with tornadoes in Oklahoma. The customer questions can arrive for good reason.
Oklahoma experiences more tornadoes per square mile than any other place in the country, but it's also become popular for data centers because of it energy costs and electric grid.
Google is investing some $700 million in data centers in Mayes County, about 130 miles from Oklahoma City.
The area around and to the southwest of Oklahoma City "has perhaps the greatest frequency of tornadoes in the U.S.," said John Snow, a professor of meteorology at the University of Oklahoma. But he said, "tornadoes are still very rare events at any particular location, even in the bulls eye."
"It is just that compared to the rest of the nation, tornadoes are somewhat less rare here than elsewhere," Snow said.
The May 20 Moore, Okla., tornado was an EF5, with winds estimated at 210 MPH, and it struck less than 20 miles from Perimeter's data center.
But the Moore storm was a rare event. About 95% of all tornadoes are below EF3 intensity, and only 0.1% achieve EF5, according to a National Oceanic and Atmospheric Administration.
"It can sometimes take a little education on our part to explain that the true risk of the facility getting damaged by a tornado is very unlikely," said Currie. "Unlike hurricanes or earthquakes that inflict damage over hundreds of square miles, tornadoes bounce along the ground and damage infrastructure maybe a mile wide for a few miles."