USA: Initial Dredging Work at Bonner Bridge Completed
Crews with the N.C. Department of Transportation and the Great Lakes Dredge and Dock Company LLC Dredge Alaska completed dredging operations Sunday night at the Herbert C. Bonner Bridge on N.C. 12 over the Oregon Inlet in Dare County.
“I want to sincerely thank all of the hardworking NCDOT crews and the dredge crews for pushing through the harsh elements to try to complete this repair work as soon as possible,” said Transportation Secretary Tony Tata. “I also want to thank the residents of the Outer Banks for their patience during this process, and our outstanding NC Ferry employees for all of their efforts to keep the residents connected.”
Initial scans are promising; however, it will be several days before NCDOT can determine the success of the dredging. Approximately 30,000 cubic yards of sand were pumped during the weekend from the main navigation channel of the Oregon Inlet to the location at Bent 166 underneath the Bonner Bridge where scour, or the erosion of sand from bridge pilings, caused NCDOT to close the bridge on Tuesday, Dec. 3.
Yesterday, crews with NCDOT’s Location and Survey’s Unit conducted an underwater sonar survey of the area around Bent 166. Dive crews also did an initial inspection of the area to assess if the sand is compacting as it needs to in order to properly support the bridge.
To give sand time to settle and compact, NCDOT engineers are currently planning to perform another dive and sonar survey at Bent 166 on Wednesday, weather and current permitting. NCDOT officials will then evaluate data gathered at this time to determine the overall effectiveness of the sand placement and determine the next steps for repairs.
In addition to work taking place on the support structure underneath the bridge, NCDOT is also performing a survey of the deck in the area of Bent 166 to make sure that there has not been any movement of the bridge.
NCDOT awarded a $1.6 million contract to Carolina Bridge Company Inc. of Orangeburg, S.C. last week for emergency repairs on the Bonner Bridge.
Crews will use sandbags and four-foot tall A-Jacks to provide support to the bridge pilings and to prevent further scour from occurring. A-Jacks interlocked together will be placed around the perimeter of the support structure at Bent 166. Crews will then place sandbags inside the line of A-Jacks. An additional two layers of A-Jacks and sandbags will then be placed on top of the base layer for a total of 10-12 feet of additional protection. This will allow sand to collect over the sandbags and A-Jacks, providing additional support to the structure.
Contractor crews have begun mobilizing equipment and materials to the bridge site. NCDOT and the contractor are working together to develop a timeframe for the repairs to be complete.
In addition to the emergency repair work, Carolina Bridge Company Inc. will also begin driving two test piles later this week near the general vicinity of Bent 166. These test piles will allow NCDOT’s geotechnical staff to gather data about the load piles can carry, and will help in the analysis of this situation, as well as for future repairs.
Press Release, December 10, 2013