The N.C. Department of Transportation wanted to build a new bridge to replace the existing 1950s era swing bridge over the Intracoastal Waterway on N.C. 50/210 in Surf City. This was one of two bridges providing access to Topsail Island, and as such, it was imperative that the structural capacity of the bridge be improved so that the bridge had sufficient capacity allowing for emergency access, hurricane evacuation, and acceptable travel times.
The plan was for the existing bridge to be removed and have the replacement bridge constructed parallel and to the west of the existing bridge. The new bridge was a 3,773 foot, 29-span bridge.
Froehling & Robertson, Inc. was brought on board to provide all subsurface investigations and foundation recommendations. This was accomplished by initially performing roughly forty borings, some in water as deep as fifteen feet.
At the completion of the field work, all collected field samples were returned to F&R’s offices for classification and laboratory testing. This work included geotechnical/index classification tests (e.g. gradation and Atterberg Limits), moisture content tests, consolidations, and triaxial tests.
Finally, detailed recommendations were made to the NC Department of Transportation regarding foundation requirements and environmental factors that must be considered during the bridge’s design phase.