Patroon closes at 7:00 p.m. every evening and must be open every morning at 5:30 a.m., Curley says. If the team misses the opening deadline, it will be fined $10,000 every 5 minutes for the first 30 minutes and then $250,000 plus $10,000 for every five minutes thereafter, he adds.

That is one of several concerns for the team. "We have some environmental considerations because there are sturgeon [an endangered species] in the river and two of the piers are in the water," Curley says. To protect the endangered species, no work can be performed during its spawning season from April to June.

"We have over 400 bearings [for the whole project] to replace. The most difficult of these are located in the Hudson River, which is difficult because of the sturgeon and because we are working over the water 80 or 90 feet in the air with very heavy loads," Curley says.

To remove and replace bearings on Patroon at those two piers, the team will work off barges to set up jacking towers on the existing pier footings and jack up the bridge. "These piers carry the main bridge trusses and will require the installation of new bearings with a vertical load capacity of 2,700 kips each," Curley says.

The I-90 project has about 25 piers and all but nine will be demolished and replaced while traffic is maintained, he says. The nine that are not replaced must be brought up to seismic code, he adds.

ANOTHER APPROACH

Meanwhile, under the Transportation Research Board's (TRB) Strategic Highway Research Program (SHRP2) ABC toolkit, another DOT project is on a super fast track. The federally funded $10.2-million project involves demolition and replacement of twin bridges carrying I-84 over Dingle Ridge Road in Southeast, N.Y.—in just two weekends.

Led by the GC, Yonkers Contracting Co., the team is replacing the 134-ft-long and 33.4-ft-wide bridges with two three-lane bridges that are 80 ft long and 57 ft wide with full shoulders. The new bridges include prefabricated bridge elements, supplied by Daily Precast, Shaftsbury, Vt., which are assembled alongside the existing structure and then slid into place.

The first slide—the westbound bridge—occurred Sept. 21 and took only 20 hours with traffic diverted to a nearby roadway, says Bala Sivakumar, vice president and director of special bridge projects at HNTB Corp., project designer and TRB's ABC toolkit developer. DOT is the civil engineer, and Marino, a Barnhart company, is the slide subcontractor.

The team used cast-in-place methods on site for the abutments and foundations and worked below the existing bridge so that traffic would not be disrupted, Sivakumar says. "While that work was going on under the bridge, next to the bridge they assembled the superstructure using precast concrete double-T beams," he adds. After removing the old bridge, the new one was slid onto newly built abutments and the roadway raised about 2 ft to meet the new bridge.

While the slides will be done in two weekends, the entire project including approaches and roadwork began last February and is set for completion in late December. The eastbound lane slide is set for Oct. 19.

"This is a hybrid superstructure, and approach slabs follow the guidelines given in the toolkit," Sivakumar says. "It melds the ABC aspects with traditional construction of the superstructure." This is only the second demonstration project under the SHRP2 ABC program, he adds. The first was the Keg Creek Bridge in Iowa, completed in 2011. "The difference between the Iowa and New York projects is that in New York [precast elements] are being assembled alongside the structure while in Iowa they were assembled in place," he adds.

As for the future, both Sivakumar and McDonald say they see ABC as a small but growing trend nationwide as more and more state DOTs take steps to save costs by, for example, bundling bridge projects together and using partnerships.

On the latter, NYSDOT has met with its counterparts in Massachusetts, Missouri and other states that are also using ABC. "We did a lot of research to see what would work and [shared] lessons learned," McDonald says.

"I think the message is that there is a clear recognition from state DOTs and from the construction and engineering industries and organized labor that there is not sufficient funding to make all the investments that we need to make," she says. "Everybody is being much more innovative and collaborative" to ensure that the funding they get goes as far as possible.