Bridge Removal Continues with Guillotine-Like Blades
Crews continue to dismantle the Herbert C. Bonner Bridge, located in the Oregon Inlet of North Carolina. The project is expected to reach completion by early 2020.
Built in 1963, the bridge has served thousands of vehicles over nearly six decades, suffered boat and barge collisions and battled harsh ocean elements and intense currents that, at times, almost caused it to lose its footing.
About the Replacement Bridge
The Herbert C. Bonner Bridge replacement project (later known as the Marc Basnight Bridge) approval was first announced in August 2015, after various legal obstacles from environmental groups halted construction. At the time, the project was reported to begin in the spring of 2016.
Photos: Bonner Bridge deconstruction continues. See the Outer Banks bridge over the years. https://t.co/Iot0iME2Pv— Winston-SalemJournal (@JournalNow) August 31, 2019
Former Gov. Pat McCrory indicated the terms of a settlement agreement reached in June had been met, and the environmental groups represented by the Southern Environmental Law Center—which included the Defenders of Wildlife and the National Wildlife Refuge Association—had dropped all remaining lawsuits that stood in the way of construction.
During building efforts in 2017, however, crews working on the new Herbert C. Bonner Bridge drove a steel casing into the three underground transmission cables that bring power to Hattteras and Ocracoke Islands, causing damage to two of the three cables, according to the Cape Hatteras Electric Cooperative. Because of the incident, more than 7,600 homes and businesses were affected, according to The Virginian-Pilot.
Only a few days after the incident, the contractor responsible was sued by residents in a court action filed before power even returned in many communities.
By May 2018, the firm responsible for the power outage incident, PCL Construction (Denver), reached a $10.3 million settlement with local businesses and residents. Breaking the agreement down, the firm will pay $8.1 million to businesses and $2.25 million to residents and renters in the area affected by widespread blackouts and evacuations that lasted nearly a week after the outage.
The settlement was ordered by U.S. District Court Judge James C. Dever III.
To reach maximum efficiency, the bridge was divided into five regions and consisted of three or four 54-inch diameter vertical concrete cylinder piles, transition and long navigational spans that used a combination of cast-in-place reinforced concrete pile caps with six to 30, 36-inch square concrete piles in a battered configuration to further resist wind and ship impacts.
In total, work on the project, which opened to traffic on Feb. 25, used 690 piles measuring over 15 miles in length combined.
Most recently, in June of this year, Deep Foundations Institute (Hawthorne, New Jersey) announced the $252 million, 2.8-mile Marc Basnight Bridge was the recipient of its 2019 DFI Outstanding Project Award.
The Basnight Bridge team consisted of engineering company HDR, general and foundation contractor PCL Civil Constructors, and owners the North Carolina Department of Transportation. The team is slated to be presented with the award at the DFI 44th Annual Conference on Deep Foundations Oct. 15-18, in Chicago.
The new bridge is expected to have a 100-year service life.
What’s Happening Now
After starting deconstruction in April, the North Carolina Department of Transportation has reportedly extracted 374 of 1,619 piles and removed 46 of 187 spans. In total, 70,000 tons of debris is expected to be removed and unloaded offshore where portions will be used at four different existing artificial reefs.
“It’s quite an epic undertaking,” said Pablo Hernandez, resident engineer for the North Carolina Department of Transportation. “You have to be very deliberate in how you remove the structures.”
In order to remove these piles and spans—some piles reaching 6 feet in diameter and 130 feet long—the crews are using a special machine with a 6-foot saw blade to make an initial gap. The endeavor is also implementing a hydraulic-powered blade.
According to Hernandez, the hydraulic-powered machine doesn’t actually spin the blade, nor does it have teeth like a saw. Instead, the machine pushes through concrete and steel, similar to a slow-moving, horizontal guillotine. The technique is reportedly safer for the high areas over the water.
Once a section is cut free from the bridge, a crane outfitted with a giant fork then removes the concrete portion and places it on a barge for offshore hauling. This is allegedly the toughest part of the dismantling process, as large hoses are also used to jet water into the bottom and around the columns to remove sand, while the large cranes gradually lift them.
The deconstruction project is expected to be complete by early 2020 with 1,000 feet remaining at the south end of the bridge as a walkway and possibly a fishing pier, depending on federal permits.