During an inspection along Interstate-95 in Prince William County, technician Bernie Sevilla places an ultrasonic transducer atop an anchor bolt. The sound waves show no crack or irregularities in the roads, which are scheduled to inspection every five years.
"I am setting it now to a 100-inch range, and you can see that we have a spike at 51 inches down," he says. "It's reading the length of the bolt, the anchor bolt."
Sevilla and a few other technicians with the Virginia Department of Transportation are using new technology to monitor the state's infrastructure stress. Over time, roads, bridges, and even highway signs eventually begin to wear down under the weight of countless cars and rigs, so staying ahead of maintenance is important.
"I don't know if you could do this type of inspection without this equipment," says VDOT technician Craig Freidline. "We are testing the bolt below concrete level."
To detect problems hidden from the naked eye, the inspection teams employ high-tech devices on hundreds of signs and bridges along the interstate. They use ultrasonic devices, ground penetrating radar and infrared thermographics.
"The way that works is you are looking for what we call de-lamination, which is the separation of concrete into different layers," says Nicholas Roper, VDOT's structure and bridge engineer for Northern Virginia. "So it would indicate where you have a discontinuity, that would mean there is a fissure or a de-lamination there."
Dealing with decades-old infrastructure
No matter how much transportation maintenance any state performs, there is no way to turn back the clock on aging infrastructure. At the D.C.-based think tank Bipartisan Police Center, visiting scholar Emil Frankel, a former assistant transportation secretary under George W. Bush, says bridges on the interstate system are generally 40 to 50 years old.
"The lifetime of bridges is estimated to be 40 to 50 years," says Frankel. "So bridge problems, structural deficiencies, even more serious risks than that, are not unexpected. Many of them are coming to the end of their lives. But the difficulty is what we do about it. We can discover the problems but remedying the problems is quite another issue."
Frankel says the bridges that were built decades ago were not designed to withstand today's standards.
Modernizing the nation's infrastructure carries an astronomical price tag. The American Society of Civil Engineers estimated in 2009 that the five-year investment needed to improve all infrastructures--from aviation to roads, bridges to levees, dams to drinking water--was $2.2 trillion dollars.
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Photos: Stress on local roads and bridges