N.C. Department of Transportation crews conducted several tests and surveys of the Herbert C. Bonner Bridge on N.C. 12 over the Oregon Inlet in Dare County.
These tests allowed the department to gather crucial information to help evaluate the overall effectiveness of the sand placed in the area where erosion occurred and determine the next steps for repairs. Results of the information gathered should be available on Thursday.
As part of the testing, crews with NCDOT’s Location and Surveys Unit conducted an underwater sonar survey of the area around Bent 166. Dive crews also inspected the area to assess if the sand is compacting as it needs to in order to properly support the bridge.
The department also began testing how much weight the bridge piles can carry. Carolina Bridge Company Inc. will drive two test piles into the inlet floor near the general vicinity of Bent 166. As of 4:30 p.m., they had completed one test drive.
NCDOT’s geotechnical staff will use the data gathered, as well as additional surveys, to fully assess this situation and future repairs. Once a full assessment of the bridge’s safety is complete, NCDOT will determine the next steps. According to NCDOT Division 1 Engineer Jerry Jennings, the timeframe for reopening the bridge could be about a week from now or up to 90 days, depending on the findings of the assessment and timeline for repairs.
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.
Emergency Repairs
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 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.
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Press Release, December 12, 2013