Mount Rushmore’s New Preservation Technology
Look closely, and you might discover one of Mount Rushmore’s biggest secrets: 8,000 feet of camouflaged, strategically placed copper wiring that has helped engineers monitor 144 hairline fractures in the iconic monument since 1998. But copper’s conductive properties can make the cracks worse during thunderstorms (and besides, copper is so, well, 1800’s). So come spring, 2009, engineers will replace them with 1,000 feet of new, fiber-optic cable—a $250,000 endeavor that will help engineers preserve Mount Rushmore for years to come.
That’s great news for the roughly two million travelers who flock to the state’s top attraction each year—even in winter (the national monument is only closed one day a year: Christmas). The 60-foot-tall famous faces of George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln have seen some wrinkles over the years—not surprising, since countless sticks of dynamite helped carve their visages in granite. And given the area’s extreme temperatures (which can fluctuate from minus 20 to 120 degrees Fahrenheit throughout the year), it’s not surprising that cracks are inevitable.
To minimize the damage, a team of engineers monitors Mount Rushmore’s cracks so they can be sealed before doing real damage. The existing wiring, which measures the rocks’ movement every four hours, has been a good “early warning system,” according to monument engineer Paul Nelson. But the fiber-optic cables will be even better, he says. And now, from a bunker-like station behind the mountain monument, a new computer data collector will check the high-tech cables and detect any potential threats to the structure.
Long before engineers were able to survey the state of mountain from a central computer, the job fell to the original sculptors to preserve the rock as they carved it, applying a mixture made up of white lead, granite dust, and linseed oil to help keep the water out.
“This formula was never written down,” says Nelson. “It was just handed down from maintenance employee to maintenance employee.”
Fast-forward to present day; Rich Barry, an engineer at the monument and part of the expertly trained “Rope Access” squad, fixes any trouble spots by rappelling two stories down the face of Rushmore with a silicone-filled caulking gun under one arm.
“Over time, as technology provides more options, upkeep gets easier,” Barry says. Even though Barry has been up close and personal with all four presidents for nearly 10 years, the site never fails to amaze him.
“The guys that carved this thing did an amazing job,” he says. “It’s a great privilege to be on Mount Rushmore and see the work that close.”