One of the most famous bridges along the East Coast must be demolished as quickly as possible, begging the question: Will the Bonner Bridge along North Carolina’s Outer Banks go out with a bang?
A big, dramatic explosion would definitely be a memorable way to say goodbye to the 55-year-old bridge, but engineers say their plan is just the opposite. That’s partly because flying debris could damage the replacement bridge that just opened a few weeks ago.
Instead, the 2.7-mile bridge on N.C. 12 is going to be painstakingly sawed apart, piece by piece, and carted off on barges. The work has already begun and should take about 10 months, officials told the Charlotte Observer.
“The whole thing will be dangerous, because we are compromising the structure of the bridge as we go,” said the project’s resident engineer, Pablo Hernandez. “We’re doing it in a controlled fashion, but when you cut things loose, they can swing away from you in directions you didn’t predict.”
Here are some of the lesser-known details of the demolition project, according to Hernandez:
- There are oddities lost under the bridge: Over the past 50 years, the state has dropped countless oddities under the bridge to stabilize the sand around the pilings. Boulders, baskets and metal mattresses filled with rock, and gigantic jacks (like the children’s toy), are just a few of the things 30 feet below the surfaces. Some must be removed, but the project’s engineers aren’t exactly sure where some are located, because they were placed on the bottom more than 30 years ago.
- 1,000 feet of the old bridge is being kept intact for a surprising reason: The N.C. Department of Transportation is keeping 1,000 feet of the Bonner Bridge intact at the south end, as a pedestrian and fishing pier. But that is only part of the reason it was saved. Turns out a strong current of water called the Davis Slough flows under that section of the bridge, and removing it would change the flow pattern in Oregon Inlet in ways that could not be easily predicted. Beach erosion and rough currents could result.
The bridge’s end posts have been saved: The 4-foot-long end posts (with marble plaques) at the north end of the bridge were sawed off last week and are being saved as historic artifacts. They will eventually go on display.
The bridge’s bits and pieces will be added to existing man-made reefs: The concrete and metal will be hauled out to sea on barges and dumped into the ocean to enhance four artificial reefs. The sites are 5 to 12 miles off of Oregon Inlet. (No asphalt will be included for environmental reasons.)
- Disturbing marine mammals and reptiles is forbidden during the work: If a dolphin, sea turtle, manatee, whale or any other marine mammal swims up to the bridge or under it during work, everything must stop until the animal has moved away.
- Not all of the pilings that held up the bridge will be removed: Project planners and environmentalist have determined that removing the pilings in marshes at the north end of the bridge will cause harm to the sensitive wetlands and marine life, so pilings in those areas will be cut off at ground water level.