Carolina TEA, as a subconsultant to KCI, is leading the structures design for the seismic study, retrofit, and/or replacement of the US 278 bridges over Mackay Creek and Skull Creek (the Intracoastal Waterway).

The 2,230 ft Mackay Creek east-bound lane is structurally deficient and will be replaced. The remaining bridges (2,230 ft Mackay Creek west-bound lane and 2,823 ft Skull Creek bridges) will be replaced as well. Two causeways within the project limits may need to be widened and may become part of the structures scope of work. The team is tasked with studying the existing bridges to determine the viability of widening and/or retrofitting the existing structures to perform adequately for anticipated seismic levels for the area.

The seismic report was completed in Summer 2020 and included retrofit options, a summary of available outcomes, construction cost estimates, and a Life Cycle Cost Analysis of the options.

A preferred alternative has been selected including a new 8,000 ft long bridge carrying 3 lanes in each direction as well as a 15’ multi-use path, with an on-structure interchange at Pinckney Island – a federally protected bird sanctuary and a USFW boat launch. The bridge will be placed 65’ clear over ordinary high water at the ICWW. Public interest in the project is very high, with many at Hilton Head and Beaufort County desiring a new “Gateway” onto the island, and others desiring a reduction in US 278 capacity.

Replacement options are required to maintain 2 lanes of traffic in each direction as a minimum. Power, water and fiber for Hilton Head Island parallel the bridges in the study corridor and will be impacted by the selected alternative.