Progress continues on the Indian River Inlet Bridge in Delaware. The $150 million project is being constructed by Skanska USA Civil Southeast Inc., for the Delaware Department of Transportation (DelDOT). In its second year of construction, the bridge should be complete by the end of 2011.
Work on the project began in September 2009, with funds coming from the Federal Highway Administration (80 percent) and the State of Delaware through DelDOT Transportation Trust Funds (20 percent).
The project is design-build, which allows for one contractor to design, construct and inspect the bridge structure in one contract rather than multiple contracts. The bridge is a signature stay cable bridge with a total bridge length of 2,600 linear ft. (792.5 m) across the Indian River Inlet in the middle of Delaware Seashore State Park. It will include a 900-ft. (274.3 m) clear span over the inlet, with 1,700 ft. (518.2 m) of bridge decking over the land. All supports will be out of the water, which will eliminate conditions that are currently found with the existing bridge.
“The reason for replacing the bridge is the severe scouring that has taken place over the years,” said Dennis O’Shea, assistant director of design of DelDOT. “The Army Corps first reported evidence of significant scouring in the 1980s after an underwater survey indicated that the bridge supports, also known as piers, in the inlet were exposed and undermined.”
During the summer 2010, the contractor began the installation of 152 cable stays, and this portion of the project will continue over the next few months.
“This has allowed for the removal of some of the falsework [supporting form work] as the weight loads are now being carried by the newly installed stay cables,” said Tina Shockley DelDOT’s community relations officer. “Once all the stay cables are installed, precise tensioning will be provided to each cable to allow for even weight distribution of the bridge deck.”
The contractor constructed a form traveler that could be attached to the end of the bridge over the inlet, allowing the bridge deck over the inlet to be built. Shockley explained that for each section, forms are built and concrete is poured and allowed to cure.
Approximately every two weeks, the form traveler moves 24 ft. (7.3 m) to allow for the next concrete section to be poured. Additional edge girders also allow for the installation of cable stays, and plans are for the two sides of the bridge to meet by the summer.
“This 200-plus ton form traveler is designed specifically for the Indian River Inlet Bridge structure,” Shockley said. “It cannot be used on any other bridge. Therefore, following its use on this bridge, it will be disassembled and recycled.”
Since it is unique to the bridge, the design and construction of the form traveler presented a challenge. It required extensive and precise calculation to ensure that the newly constructed bridge could safely support the weight of the traveler and the concrete it would be supporting during all stages of construction.
At this time, the contractor’s equipment list includes two crawler cranes, rough-terrain hydraulic cranes, post-tensioning and stressing equipment, the form traveler, dozers, excavators, manlifts, extendable fork lifts, tower cranes, pump trucks and concrete screed machines.
Shockley noted that the project fell slightly behind schedule in early 2010 due to an unprecedented snowy February that required Delaware’s governor to issue several executive orders declaring states of emergency. Some of the building activities were delayed at that time.
“The weather in general at this location along the East Coast has presented a host of challenges,” Shockley said. “Nor’easters, heavy rains with flooding, foggy conditions, snowy weather and strong winds have challenged workers and the project schedule.”
Roadway approaches to the bridge will be built through another forthcoming contract.
“Due to the need to synchronize the opening of the roadway approaches with the new bridge, and noting that the current bridge construction is slightly behind schedule, the Roadway Approach Project has been slightly delayed,” Shockley said.
The new bridge will have a minimum 100-year design life. It is a four pylon tower suspension bridge design that incorporates cast-in-place concrete and epoxy-coated reinforcement steel. The foundations will be supported on 36-in. (91.4 cm) square piles.
Once complete, there will be four traffic lanes and a pedestrian walkway. The bridge will include two 12-ft. (3.6 m) wide travel lanes, a 10-ft. (3 m) wide outside shoulder, and a 4-ft. (1.2 m) wide inside shoulder in each direction. Additionally, a 12-ft. wide sidewalk will be accessed from the east side of the bridge.CEG
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