The two existing U.S. Highway 17 bridges over the Cooper River were functionally obsolete, with too-narrow lanes, limited capacity and substandard vertical and horizontal ship channel clearance. In an effort to improve traffic safety and increase overall capacity, the South Carolina Department of Transportation (SCDOT) undertook the monumental effort of designing and constructing a replacement crossing.
The ultimate solution – a $531 million, two-and-a-half-mile-long bridge with a 1,530-foot cable-stayed main span – is the single largest project in SCDOT history.
Completing design and construction of a project of this magnitude within a five-year window necessitated use of a design-build procurement method. In addition, challenges stemming from the project's location and its incredible size required a unique approach to such project elements as construction inspection and project controls.
The structure spans the mouth of the Cooper River at Charleston Harbor and replaces Grace Memorial Bridge (built in the late 1920s) and the Pearman Bridge (constructed 40 years later). The bridge links the city of Charleston and the town of Mount Pleasant
The new bridge was designed to accommodate ship traffic to a world-class port, withstand seismic events like Charleston's 1886 earthquake (magnitude 7.3), weather hurricanes like Hugo and be aesthetically pleasing enough to satisfy the discerning public eye. The new structure also meets long-term traffic needs with eight vehicular lanes, and pedestrian and bicycle accommodations.
The new bridge was essentially five major projects in one: two large interchanges, two approaches and the main span. The awe-inspiring, cable-stayed main span boasts a deck almost 200 feet above the water of Charleston Harbor's shipping channel and two diamond towers almost 600 feet high.
SCDOT is the project owner, and the T.Y. Lin International/HDR joint venture provided design review coordination, elements of design review, and full construction engineering and inspection services. A separate team of consultants was responsible for actual design and construction.
On either side of the Cooper River are wetland areas. The Santee-Cooper River Basin comprises the second largest Atlantic coast watershed in the United States and is home to more than 125 fish species, including the federally protected shortnose sturgeon, an abundance of waterfowl and loggerhead turtles. Special concerns center on the nesting loggerheads that lay their eggs on the beaches and find their way back to sea via moonlight. Because a bridge adorned with too many lights could directly and negatively impact the turtles' migration pattern, designers planned limited and directional lighting for the new structure. For these and other reasons, environmental mitigation on the project site was particularly important.
The South Carolina Department of Transportation Received the following 2006 Awards
Palmetto Award for Engineering Excellence, Transportation, Projects Over $10 Million, Engineering Excellence Awards
American Council of Engineering Companies, South Carolina
Merit Award, Outstanding Civil Engineering Achievement
American Society of Civil Engineers
Grand Award, Engineering Excellence Awards
American Council of Engineering Companies
Gustav Lindenthal Medal, Bridge Awards
International Bridge Conference
Outstanding Civil Engineering Achievement Award
American Society of Civil Engineers, East Coast Branch
AASHTO President's Transportation Award, Environment
American Association of State Highway Transportation Officials
Excellence in Highway Design Awards
Federal Highway Administration