This Cat 140H CCA0284 G4 motorgrader is just one of many pieces of Cat iron involved in the project.
Skidaway Island, a barrier island off the coast of Savannah, Ga., bordering Skidaway Straights, which is part of the Atlantic Intracoastal Waterway, is linked to the mainland by Skidaway Narrows Bridge. Part of the Diamond Causeway, also known as the Georgia 204 spur, the bridge is nearly 40 years old and by all accounts, in dire need of repair.
Years of waiting for state officials to fund construction of a new bridge have finally come to an end for the island’s approximately 10,000 residents. The Georgia Department of Transportation (GDOT) agreed to accelerate the replacement of the aging Skidaway Narrows Bridge, awarding a $22.5 million contract to United Contractors Inc., Great Falls, S.C, for construction of a new bridge. Eighty percent of the money comes from federal funds, the other 20 percent from the state.
Out With the Old…
Labeled structurally deficient by the state, the existing bascule bridge is prone to frequent malfunctions, but offers the only way off the island for vehicular traffic. Local lawmakers dubbed the project a priority nearly a decade ago, but a lack of funds and permit problems impeded several attempts to implement the planned replacement. State Sen. Eric Johnson also blamed part of the delay on construction of Whitfield Avenue in Savannah.
However, when the I-35W Mississippi River Bridge in Minneapolis collapsed in 2007, it renewed attention on Skidaway. Considering replacement of the bridge a safety issue, County Commission Chairman Pete Liakakis told local media that the Skidaway Bridge has malfunctioned a number of times — “and they don’t make spare parts. If some kind of disaster hit Skidaway, like a hurricane, we’ve got thousands of people who are going to be in trouble.”
Evacuation concerns aren’t centered entirely on the bridge’s age; there are safety-related concerns emanating from its condition. Barry Dragon, director of the bridge program for the 7th district, refutes the alarm regarding the possibility of a drawbridge malfunction leaving island residents stranded during a hurricane evacuation. Moveable bridges normally don’t break in the “up” position, he noted. “If a hurricane is coming, we authorize the owner to lock down. Generally, that’s eight hours prior to the forecast arrival of hurricane-force winds. We’ve never had a problem as far as evacuating, and I’ve heard every story there is.”
The Skidaway Bridge is one of about 250 moveable bridges in the Coast Guard’s 7th District, which includes Florida, Georgia, South Carolina, Puerto Rico and the Virgin Islands. Today, bridge owners generally prefer high-level fixed bridges to moveable ones, Dragon said. Moveable bridges are expensive to operate and run, in part because they require bridge tenders.
“Their lifespan is the same as fixed-span [bridges], but their costs are higher. All of them are one-of-a-kind; if a part breaks, you have to have it made. It’s not [on] the shelf,” Dragon explained.
Plans also are in place to replace the county’s other bascule bridge, located at Causton Bluff, according to Tom Thompson, executive director of the Chatham County-Savannah Metropolitan Planning Commission. Federal stimulus funds will cover most of the cost of the design of a new bridge.
By replacing the aging structure with a fixed-span bridge, vehicular traffic won’t be interrupted for passing boat traffic. The two-lane concrete bridge will have a clearance of 65 ft. (19.8 m) to allow boat traffic to pass without having to wait for an opening and will help prevent Skidaway’s estimated 10,000 residents from getting stranded on the island.
…and in With the New
Officially known as the Roebling Bridge, the Chatham County two-lane drawbridge over the Intracoastal Waterway is named for Robert Roebling, who donated land on the island for an oceanographic institute. Roebling is the great-grandson of John Roebling, who designed the Brooklyn Bridge, and the grandson of Washington Roebling, who served as the chief engineer during construction of the Brooklyn Bridge.
Its replacement will be a two-lane, high-level fixed-span bridge, constructed parallel to and north of the existing bridge, within the existing right-of-way. The design-build contract includes construction of a bridge and approach on the SR 204 Spur over the Skidaway Narrows, said Craig Solomon, communications officer for the GDOT.
The new high-rise bridge will be 3,220 ft. (981 m) long and 38 ft. (11.5 m) wide, including two 11-ft. (3.3 m) lanes with 8-ft. (2.4 m) shoulders. Bike lanes will be included on the shoulders. The minimum clearance over the navigable channel is proposed at 65 ft. (19.8 m) above mean high water.
Preliminary work on the new bridge began with an engineering test to determine the depth needed for the bridge’s pilings. Engineers applied 1,200 tons (1089 t) of force to a 3 sq. ft. (.28 sq m) concrete pile already driven 30 ft. (9 m) into the ground, with sensors recording the effects. The test was repeated in the water to determine how deep the piles have to be driven there.
County officials and others broke ground on the project July 30, but Solomon said work didn’t get started until Dec. 5, 2010, under the direction of GDOT Project Supervisor Binyam Araya. Expected to be completed by July 31, 2013, Solomon said, and work is currently on schedule.
Staying on schedule could be a challenge. Not only is the new bridge being built without interrupting traffic on the existing bridge, but crews will be working from barges. Solomon said about 40 crew members have to work around heavy traffic while the only existing bridge remains open to allow people to get on and off the island. He also mentions environmental issues involved in working around a body of water.
Several major subcontractors are already on site. Tricor Construction Inc., from Spartanburg, S.C., is working on a reinforced earth retaining wall. Scott and Sons Trucking, Rincon, Ga., is hauling dirt. So far, roughly 15,000 cu. yds. (11,468 cu m) of dirt have been used. Triad Supply Services Inc., Pembroke, Ga., is responsible for seeding and erosion control. Border Rebar LLC, Gastonia, N.C., is overseeing stay-in-place deck forms and furnishing tie rebar steel. Long Engineering, based in Atlanta, is providing civil engineering services.
Several cranes have been employed on the project, including a 100F Link-Belt 150-ton (136 t) crane, 160-ton (145 t) Link-Belt cherry picker, 1610 American 150-ton crane, Link-Belt 238 200-ton (181 t) crane and a 1611 Link-Belt 120-ton (109 t) crane.
The laundry list of equipment working on the job also includes a Cat D25D AOT3 articulated dump truck, a Bobcat T300 B060 track loader, Cat 140H CCA0284 G4 motorgrader, Cat 325 BH29 motorgrader, Cat 420D B8 backhoe, Cat D95XL W9BO3244 D2121, Ford F Series TR 134, Hamm 3307 28135 drum roller, Ice Hammer I-42 and I-46 pile hammers, Komatsu 51PX 2835 dozer, Massey Ferguson 253 4WD tractor, Wacker BP 3534P and two hydraulic pushers.
The last phase of the project involves removal of the existing drawbridge on Diamond Causeway. If work on the new bridge remains on schedule, demolition should begin July 31, 2013. CEG