Crews taking down N.C.’s Bonner Bridge
70,000 tons of debris will be unloaded offshore on four artificial reefs
OREGON INLET, N.C. — Old Bonner Bridge is coming down.
About a half mile of the center of the well-worn structure is gone, hauled offshore in massive pieces for its new purpose — an artificial reef.
Over nearly six decades, it endured thousands of vehicles traveling daily over its surface, barges and boats colliding into its pilings, harsh Outer Banks elements rusting the joints and swirling currents nearly taking out its footing.
The new $252 million, 2.8-mile Marc Basnight Bridge over Oregon Inlet opened in February and is supposed to last 100 years. It is made with stronger concrete and steel, able to better resist the elements and boat collisions. Seven of its center spans measure 300 feet wide, much more accommodating for vessels to pass under and stay in the channel. The new bridge won several construction and engineering awards.
In April crews began dismantling the old span.
Everything about the project is large, heavy, demanding and dangerous. No bridge of this size has ever been taken apart before in North Carolina, said Pablo Hernandez, resident engineer for the North Carolina Department of Transportation.
“It’s quite an epic undertaking,” he said. “You have to be very deliberate in how you remove the structures.”
In all, 70,000 tons of debris will be unloaded offshore on four different existing artificial reefs. Each barge hauls about 1,100 tons per load. As of this week, 374 of 1,619 piles have been extracted and 46 of 187 spans removed. Some piles wrenched from the inlet bottom are nearly 6 feet in diameter and 130 feet long.
Crews have removed sections from the north end as well as the middle. The project is expected to be finished in early 2020.
On Monday, Hernandez eased a boat underneath the bridge and pointed high over his head to a small gap in the roadway.
“See that?” he said. “You can see daylight.”
A machine with a six-foot saw blade made that gap along the center line of the span. That cut is the first step in the razing process of each section.
A hydraulic-powered blade cuts through the structure under the roadway called the cap. The blade does not spin and it does not have teeth like a saw. Instead, it pushes through concrete and steel much like a slow-moving, horizontal guillotine, Hernandez said. The technique is safer in the awkward spot high off the water.
“It is a slow, steady force,” he said.
After it’s cut free, a crane outfitted with a giant fork will lift the 100-ton piece of concrete from its place and set it on a barge for hauling offshore.
The toughest part is extracting the tall concrete piles. Large hoses jet water into the bottom around the columns to push away sand. Cranes taller than some lighthouses gradually pull them out.
“There are unknowns in doing that,” Hernandez said. “You don’t know if they’re going to come up easy, or is it going to take more force?”
Saws cut the long pilings into pieces weighing roughly 40 tons for hauling away.
About 1,000 feet of the south end of the bridge will remain in place as a walkway over the water and possibly a fishing pier, depending on federal permits. The structure will also help stabilize channels used by boats, he said.
The Coast Guard is enforcing a rule to keep anglers from fishing within 100 yards of both the new and old bridges. It is too dangerous with large equipment operating and the tricky removal of heavy pieces high over the water.
The bridge is expected to bolster fishing in its new life at the bottom of the ocean.
“It’s quite an epic undertaking.” — Pablo Hernandez, resident engineer for the North Carolina Department of Transportation