Though progress has slowed again, the Iowa-bound span of the new Interstate 74 bridge still is expected to be finished this year.
The latest leg of work on the all-important arches is taking "longer than expected," a project official said. The raising of the arches has been rife with complications, which were largely anticipated, given the complicated nature of the design.
A highly precise undertaking, the raising of the arch ribs (segments) for the westbound span has led to a yearlong delay in getting the first bridge span open. At one time, the arch design was pitting the Iowa Department of Transportation, the lead agency on the project, against the lead contractor, Lunda Construction.
For a period last spring and summer, the two parties disputed whether the arches were "constructible" as designed. In late fall, progress picked up, and the arch for the westbound span now is two-thirds complete.
"Our goal remains the same — to open the westbound bridge in the second half of 2020," said Danielle Alvarez, project manager for the Iowa DOT. "The time frame is largely dependent on when the arch is completed.
"We are working toward completing the westbound arch in the spring. While the pace is slower than we’d hoped, we’re doing everything we can, in coordination with Lunda, to get the arch done as quickly and safely as possible."
So far, 20 arch ribs have been raised and one permanent strut is in place on the Iowa-side arch legs. Each of the four "legs" of the arch will get two more segments, then two "keystone" pieces will be raised in the center. Precise alignment is critical in order to make the arch segments meet in the middle, high above the Mississippi River.
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The first permanent strut on the Illinois arch legs is taking longer to install than expected. The struts are lateral braces that supply support and rigidity to the arch system.
In mid-January, DOT officials anticipated the Illinois-side strut would be in place by now. Despite a mild construction season, the strut work isn't yet finished. The delay is largely attributable to the support system for the arches, including cables that guide them to their correct trajectory. The cables have to be raised above 200-foot tall towers that support the arches, and they have to be precisely aligned.
"At this stage, there is a lot of preparatory work involved before an additional arch segment can be erected, including installing the upper cable stays that support the arch and adjusting the cable stays to allow installation of the permanent strut," Alvarez said. "Yes, it’s been a mild winter, but the higher the arch gets, the more challenging it becomes."
Among the challenges in a $1.2 billion project that includes building a major bridge and expanding a local interstate system is the location of the bridge work — both in and high above the channel of the Mississippi River between Bettendorf and Moline.
The safety of ironworkers, towboat captains, cement-truck drivers and everyone else involved is the first goal of the contractor and the DOT, Alvarez said.
"Lunda’s ironworkers and crane operators have been doing a great job installing each arch segment correctly and safely, which is our priority," she said. "It’s important to keep in mind there are certain steps that need to take place for each segment, including installing/tensioning (cable) stays and installing a permanent strut, that take time."
During setting of the first permanent strut, surveys showed the nearly 300 feet of arch segments that extend outward from anchorages near the Bettendorf shoreline on two arch legs are within a half inch of each other in length.
"We do not yet have final survey information (on the Illinois-side arch alignment)," Alvarez said. "While multiple surveys will be performed, the one that determines the final position is the one performed after the next set of stays are installed."