The final pieces of the arch for the new Iowa-bound I-74 bridge have been raised, but the opening of the span is again being delayed.
Two pre-connected segments that form the upper-most "keystone" of the arch were raised by crane around 8:30 a.m. Wednesday.
Though the last pieces are in place, they likely are days away from being freed from the crane that raised them.
“It looks close, but there are thousands of bolts to go,” said Danielle Alvarez, project manager for the Iowa DOT. “Once the crane is moved, the arches will be free standing, and the temporary-support system will be removed.”
While the near-completion is good news, the fact it took until early May is having an impact on the overall timeline for getting the Iowa-bound span open, Alvarez said.
Already a year behind schedule, westbound was expected to open to traffic in the second half of this year. Delays in completing the arch now are pushing that timeline to the end of the year, she said.
Dozens of spectators came and went along the bike path in Bettendorf Wednesday morning to see the historic completion of the basket-handle design arch.
The keystones have four connection points to the other arch segments, and each connection requires about 1,000 bolts. Also time-consuming is the tensioning of the system, which ultimately will result in the removal of the temporary stay cables that have been used to guide the segments into proper alignment.
The 200-foot-tall blue/green towers that supported the cabling system will be moved just downstream as workers shift their attention to the Illinois-bound arches.
As the arches are raised for the second span, the floor system for Iowa-bound lanes will be simultaneously completed.
“We have all six sections (of bridge deck) on the Ben Butterworth Parkway in Moline, and we have a little more work to do before they lift more steel,” Alvarez said.
Making a new appearance in the work zone are cables called hangers, which are attached to the arches and will be connected to the bridge deck as its suspension system.
Much has been learned, Alvarez said, from the building of the first span, especially the arch. While the experience is likely to be helpful in the raising of the second arch, there is a snag.
“The eastbound isn’t as simple as the westbound,” she said. “On the eastbound, the downstream side is heavier, due to the cantilevered bike and pedestrian path.”
The weight of the bike lane on the Illinois-bound span creates a need for the arches to be more robust, Alvarez said.
She expects the installation of the floor system on the westbound span, including its connections to the suspension hangers, will take the duration of the summer.
No new timeline has been indicated for the Illinois-bound span’s completion.
Meanwhile, the Mississippi River channel is closed to commercial navigation for 72 hours (beginning first thing Wednesday) as several cranes and barges, along with a large crew of workers, occupy the work zone. Recreational boaters are asked to used caution and avoid the area entirely, if possible.
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