In 2003, construction of the new $530-million Cooper River Bridge rose up from the water and off the ground.
Ahead of schedule, cars are expected to begin travelling the beautiful span in 2005.
The Charleston Interchange
The first clues to the construction ahead are red and blue crane booms reaching into the air. As the Cooper River Bridge replacement progresses into its third year of construction, there are more than forty cranes being used to lift and place steel casings, cages, frameworks, as well as steel and concrete girders.
For travelers heading into Charleston from North Charleston on I-26, the results of so much crane activity can be seen just before the Cypress Street on-ramp (after mile marker 219 and almost a mile from where I-26 ends in downtown Charleston). Rising to the right of the roadway, the pier caps for the new bridge’s on-ramp from I-26 eastbound begin their assent.
This on-ramp will be the highest in the four-level Charleston Interchange with 10 ft. (3 m) in diameter columns rising up to 85 ft. (25.9 m) When all the pier caps are in place on the columns and a bent is “straddled” over I-26, the on-ramp’s road deck will be constructed 90 ft. (27.4 m) in the air.
To the east out towards the Cooper River at mile marker 220, rows of columns and large pier caps can be seen stretching out along the Charleston trestle and out to Town Creek. Small pier caps perched upon single columns are in place for the Meeting Street on and off-ramps and the Morrison Drive off-ramp, which will begin in the summer of 2004.
On the ground, Meeting Street between Sheppard and San Souci Streets is undergoing renovations. The Meeting Street improvements include underground utilities, as well as new sidewalks, bus stops, street lighting and turning lanes.
Fraught with challenges, the Meeting Street renovations involve the updating of a road more than 100 years old, said Charles Dwyer, South Carolina Department of Transportation (SCDOT) project manager for the bridge project. The corduroy roadway was built using timbers laid out crosswise with layers of compressed fill.
In September and October crews placed the first two large steel box girders over I-26. Weighing 434,000 lbs. (197,000 kg) and measuring 168 ft. (51.2 m) long, 8 ft. (2.4 m) tall and 9 ft. (2.7 m), the box girders are the largest and heaviest ever placed by SCDOT.
The box girders will support the ramp that extends from the I-26 eastbound ramp to the new bridge.
Views From the Existing Bridges
Throughout 2002, it was difficult to see much of the new bridge construction from the existing bridges, since most of the work occurred in the water or on the ground. By December of 2002, the eleven drilled shafts, the base of the rock islands, the concrete footings and the first level steel reinforcement were in place for both the eastern and western towers. When the 6,250 cu. yds. ( 4,800 cu m) of concrete was placed for each of the two concrete footings –– 80 ft. (24.4 m) wide, 110 ft. (33.5 m) and 18 ft. (5.5 m) deep at their center –– the base of the diamond towers literally emerged from the rocks and started to hint at the size and scale of the tower legs to come.
Week after week in 2003, the tower legs rose segment by segment. Once the base of each tower leg was in place, jumping forms have allowed crews to ascend toward the 575 ft. (175.3 m) tops of the diamond towers.
The next process involves wrapping yellow formwork around the tower legs, setting reinforcing steel within the form and placing concrete. Once the concrete has cured, the form is “jumped” up to the next level. Each segment lifts the tower legs an additional 13.6 ft. (4.1 m).
Early last summer, in May and June, the western and eastern tower legs reached their twelfth segment, extending out to their maximum width of 172.3 ft. (52.5 m).
In August, construction reached the 16th lift of the western diamond tower legs, and the western tower crane was lifted an additional 75 ft. (22.9 m) to a height of 364 ft. (111 m). By the time crews construct the 41st lift at the top of the towers, the tower crane will have been extended 592 ft. (180 m) into the air.
Over the summer, construction began on the crossbeams. At 172.3 ft. long, 26 ft. (7.9 m) wide and 12 ft. (3.7 m) deep, the crossbeam works to stabilize the tower legs at their widest point.
The crossbeam does not support the the bridge’s road deck –– the road deck will be hung from the bridge’s cable stays 15 ft. above the crossbeam, but it begins to offer a horizontal clue to the height of the new bridge’s road deck, scheduled for construction in the summer of 2004.
The tower legs have not been the only bridge elements to rise up around the Grace and Pearman Bridges. Columns rose segment by segment as the new bridge construction worked its way across Drum Island and the existing bridges.
Once the columns are completed and the formwork is available, pier caps are being constructed. One of these pier caps was even built straddling the Pearman Bridge.
Five steps are involved in constructing pier caps: (1) jacks are placed onto the columns to support the pier cap forms; (2) pier cap forms are put into place; (3) reinforcing steel cages are placed within the formwork; (4) concrete is placed around the cage within the formwork, and once the concrete has reached sufficient strength (5) the formwork is stripped to reveal the completed pier cap.
As they are completed, the rows of pier caps being connected with steel girders from Savannah, GA. These large steel girders, weighing 45 tons (40.8 t) and extending 135 ft. (41.1 m), extended across Drum Island from Town Creek to the north of Grace Bridge.
In early October, the placement of of the first steel girders for the new bridge began to extend over the existing bridges. Each girder is approximately 125 ft. (38.1 m) long, 8 ft. (2.4 m) tall and weighs 26 tons (23.6 t). One of the two bridges will be closed as many as five nights a week for the next four months to place the 66 girders reaching from the northwest side of the Grace Bridge to the Southeast side of the Pearman Bridge.
Nearly one-quarter of the approximately 1,900 steel girders have been installed thus far in the project, according to Dwyer.
The Mount Pleasant Interchange
The heights of columns descending into Mt. Pleasant are proof that the new bridge will remain the biggest “hill” in the Lowcountry. However, unlike the steep slopes of the Grace and Pearman bridges, the new bridge will have a 4.1 percent grade. This reduction in the slope requires the new bridge to extend four tenths of a mile farther into the own before touching down.
Beginning the interchange work in Mt. Pleasant, traffic shifts and detours have been constructed. Because the right-of-way for the new bridge incorporates the path of the existing Mt. Pleasant interchange, the right hand exit from the Pearman Bridge onto the Coleman Boulevard was closed and replaced with a new left hand exit ramp last March; the US 17 traffic heading onto the Grace Bridge and off of the Pearman bridge was shifted 20 ft. (6.1 m) in May of 2003.
Shaft work has been completed on the Coleman Boulevard on-ramp along the fingers of the temporary causeway built to the right of Coleman Boulevard as it approaches the existing bridges.
Unlike the existing bridges, the new bridge will also include an on-ramp from Wingo Way and an access road from Wingo Way that loops around under the new bridge. Because it crosses over the existing interchange from the Grace and Pearman bridges, the access road from Wingo Way extending underneath the new bridge will not be completed until after traffic has shifted onto the new bridge in 2005. To alleviate cross-town traffic, the Town of Mt. Pleasant has agreed to extend Wingo Way from underneath the new bridge over to Patriot’s Point Boulevard.
Looking Up and Beyond
In the upcoming months, tower construction is to begin. Ancorage zones will be constructed and complex cable work will begin, noted Dwyer.
(This article appears courtesy of SCDOT. For more information, visit www.cooperriverbridge.org.)
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