By early summer, a newly-completed Cooper River bridge will accentuate the skyline of Charleston, SC.
Officially called the Arthur Ravenel Jr. Bridge, it will be the longest cable-stay span in North America and will connect the city of Charleston and the town of Mt. Pleasant.
The bridge will have eight lanes of traffic — four in each direction — separated by a center barrier with two primary interchanges, one in Charleston and one in Mt. Pleasant.
It will increase the capacity of U.S. 17 and is expected to accommodate growth in the area, improve traffic safety, reduce costs of major bridge maintenance and better accommodate seafaring vessels. It replaces the 74-year-old Grace Memorial Bridge and the 37-year-old Silas N. Pearman Bridge.
The total cost for the bridge construction is $632 million, with an additional estimated cost of $53 million to demolish the two old bridges.
According to Charles Dwyer, project manager for the South Carolina Department of Transportation (SCDOT), the Cooper River Bridge is the single biggest project in SCDOT history. The State Infrastructure Bank, the Federal Highway Administration, and a Transportation Infrastructure Financing Act (TIFA) loan being repaid by the SCDOT, Charleston County, and the South Carolina State Port Authority is funding the project.
Construction began in 2000 with the installation of 425 drill shafts reaching down 240 ft. (73 m) below the river. The shafts’ support columns support the pier caps.
Dwyer said it took a year to complete everything below the water, at which time crews began working on the diamond towers, This phase also took approximately a year and was completed in May 2004.
The bridge spans 1,546 ft. (471 m) between its eastern and western diamond towers. They extend 572.5 ft. (174 m) in the air, making them two of the tallest concrete structures in South Carolina. Each tower was constructed with approximately 22,000 cu. yds. (16,820 cu m) of concrete and 3,700 tons (3,356 t) of reinforcing steel.
Placement of the girders began in March 2003. After the girders were installed on the mainspan, stationary metal deck pans were set between the girders, reinforcing steel was tied between the girders and concrete was spread out to form the bridge deck. To place the concrete across the eight lanes of mainline bridge deck, crews used one of the longest concrete-paving screeds ever designed to spread and finish concrete on a bridge deck. It was manufactured by Bidwell Industries of Middletown, CT.
Dwyer said construction crews are currently focusing on the installation of the cables and the bridge deck, including the railing, signs and lighting on the bridge.
Bridge deck construction began in September 2003. The mainspan, which is the area between the two towers, is constructed of 47-ft. (14.3 m) segments and was assembled in the air. Each segment consists of two edge girders with attached cable anchorages, three floor beams that span between the edge girders and pre-cast concrete deck panels. To provide a shipping clearance, the mainspan deck is 186 ft. (56.7 m) above the mean high tide mark of the Cooper River.
“As each segment of deck was set, two cables, which will hold themainspan in place, were installed,” Dwyer said.
The cables are made of high-density polyethylene pipes to protect them from changing weather conditions and vary from eight to 12 in. (20 to 30 cm) in diameter. Each pipe is threaded with 37 to 91 cable strands and can hold more than 500 tons (454 t). The first cables were set in February 2004.
“As of today we have eight of the 128 cables left to install. Once the cables are in place and the bridge is complete, the cables will be lit with low-level lights at night,” Dwyer said.
The interchange approach bridges are constructed of steel girders with cast-in-place concrete decks. The concrete girders on the ramps in Mt. Pleasant are in place, as are most of the girders for the Charleston interchange.
The bridge includes a 12-ft. (3.7 m) bicycle and pedestrian lane along the ocean-side of the bridge from Morrison Drive to Coleman Boulevard. The bicycle/pedestrian lane runs along the outer edge of the bridge’s tower piers and offers observation sites with benches to enjoy the splendor of the Charleston landscape.
Rock islands were installed in the river to prevent out-of-control shipping vessels from running into one of the main span tower piers. The rock island will stop a ship from hitting the tower by causing it to run aground. Each rock island is approximately one acre above the water and extends down to five acres across the bottom of the riverbed.
Design/Build Services for the bridge are being provided by Palmetto Bridge Constructors, a joint venture of Tidewater Skanska Inc. and Flatiron Constructors Inc. They are independently handling 80 percent of the project’s construction.
Parsons, Brinckerhoff, Quade and Douglas is the lead bridge designer on the project.
To assist SCDOT and the Federal Highway Association in managing such a large infrastructure project, design review and construction engineering and inspection services are being provided by T.Y. Lin International /HDR.
O.L. Thompson Construction Co. of Charleston, SC, is providing all the civil work, such as drainage, grading and paving
Grant Contracting of Columbia, SC, is providing the electrical work.
Drill shafts were constructed by Case Atlantic Company of Florida.
Wando Concrete of Charleston, SC, supplied all of the ready-mix concrete to the project.
Stay cables are being supplied and installed by Freyssinet International, U.S.
According to Dwyer what makes this project most challenging is the size of the project.
“One of the greatest challenges has been to deliver over 300,000 cu. yds. of concrete to the job site in the center of the river,” he said. “So far we have been able to deliver a high quality of concrete to all areas of the job, which has been a tremendous accomplishment.”
Dwyer said the construction plans took into account potential problems and set backs because of hurricanes and other large storms.
“Workers installed additional temporary support cables to protect the bridge in the event of a large storm,” Dwyer said. “In addition, there were built-in costs and extras days for construction assuming there would be storms situations during the construction process.”
And with the storms came delays.
“Each large storm of the summer of 2004 set us back about a week,” Dwyer said. “None of the big storms caused damage to the bridge and the temporary cables have been removed.”
The bridge was approximately 90 percent completed at the start of the new year.
“As soon as the new bridge is open to traffic, the construction permit requires that the Grace Memorial Bridge and the Pearman Bridge be demolished,” Dwyer said. “Concrete portions of the bridges will be disposed to established artificial reefs off the coast of South Carolina.”
He expects travelers are anxiously awaiting the project’s completion.
“We’re all very excited about the bridge opening and expect it to be a big event here in Charleston,” Dwyer said.