The state line intersection of Illinois and Iowa is banded by the Mississippi River.
Crossings are few, relative to the raw mileage of the river, making each bridge crucially important to commerce, tourism and run-of-the-mill commuting. In the Quad Cities region, a pair of dated structures, linking Moline, Ill., and Bettendorf, Iowa, via I-74, have been carrying more than 75,000 vehicles per day, a figure that is expected to grow to 100,000 by the year 2035. The westbound bridge, which runs from Illinois to Iowa, was completed and opened in 1935. The eastbound bridge was completed in 1959 and opened in 1960. Each has more than lived out its service life.
According to Iowa Department of Transportation (IDOT) Project Manager Danielle Alvarez, this corridor improvement is a long time coming. “About half of all trips between the Quad Cities occur on I-74. We’re at the point where the need we have is exceeding the capacity of the bridge,” Alvarez told Roads & Bridges. “The old structures are outdated and don’t even have shoulders. The new bridge will have four lanes in each direction along with wide shoulders for better maintenance access and reliability.”
In a joint effort, the Iowa and Illinois Departments of Transportation are in the process of erecting a new I-74 crossing adjacent to the old one that will offer more capacity and better travel times, strengthening the linkages between these two states.
The I-74 Mississippi River Bridge project is part of a regional strategy for improving access across the river in the Quad Cities. In addition to the bridge itself, the project includes interchange ramp reconfigurations and local roadway improvements. Construction began in July 2017 and is anticipated to take place over 31/2 years. The new bridge will be more than twice as wide as the existing bridge, providing four lanes in each direction. A multi-use path on the bridge will connect to paths in Bettendorf and Moline. Between Middle Road in Bettendorf and Avenue of the Cities in Moline, I-74 will be expanded to three lanes in each direction with additional lanes at select locations.
Contractors are employing both coffer dams and coffer cells to set piers in the river.
Though the project limits define only a 5.5-mile corridor, letting has been split into seven contract blocks, each comprising a crucial piece of the overall project puzzle.
The entire Quad Cities region is seeing significant development, from residential building to business district expansion, and the I-74 Bridge is playing a big part in that. The organization of the multiple areas of the project was based on a decision related to what is, in essence, an accelerated construction schedule—a billion-dollar one.
The Iowa DOT is the lead agency for the bridgework and all river work. To date, a $322 million contract has been let to Lunda for bridge construction; a $30 million contract went to Civil Constructors for westbound viaduct work in Bettendorf; and $2.7 million was let to Valley Construction to address local road improvements. Two more road contracts are to be let in the future, which will comprise widening and reconstruction of I-74 in Iowa.
On the Illinois side, $82 million went to Kraemer in June 2017 for reconstruction from the riverbank to 7th Avenue, and Walsh is spearheading an $84 million job, let in September 2017, which follows 7th to Avenue of the Cities. The means and purpose for arranging the project in this manner is a reflection of both fiscal diligence and an effort to minimize impacts on existing traffic patterns in and around the project zone.
“Quite a bit of the new construction is off of existing alignment, because of the kink in the existing roadway, which has allowed us to make progress without massive disruptions of existing traffic patterns,” George Ryan, corridor manager and VP of infrastructure solutions for construction management general consultant Wood Group, told Roads & Bridges. “This was initially conceived as an eight-year project. It was then reduced to five years, and then reduced even further to three-and-a-half years of construction. So in big terms we’re talking $1 billion of construction in less than four years, which is quite an aggressive schedule.”
The existing, aged structures buckle up and outward across the river, so designing the new bridge on a more direct trajectory has allowed project contractors to set up a kind of loose assembly line of project staging, by which traffic flow is not expected to be impacted until 2019.
The new bridge’s alignment will make for a more direct link between Moline and Bettendorf, eschewing the old structures’ winding footprint and allowing for expansion of I-74.
Working in a marine environment of any kind bears its inherent challenges—some of which were limned in our previous coverage of the Dale Gardner Veterans Memorial Bridge—but each project is unique. As such, the I-74 Bridge project is one of a kind in “bridging” the river’s divide. Both coffer dams and coffer cells are being employed to set the in-river pier locations.
There will be four arches spanning the navigation channel, two for each structure. Each will be comprised of 15 segments, which vary in length between 36 and 65 ft. The arches will be supported on two exterior stiffening girders supporting floor beam lines which transfer the loads from the deck through the cables to the arch.
There are 15 spans that take I-74 from the abutment on the Illinois shore to Pier 16 just north of the Iowa shore. The spans vary from 148 ft to 203 ft 10 in. long, except for the main river span, which measures 795 ft. Each direction (eastbound and westbound) of the bridge will include a roadway width of approximately 72.5 ft supported on seven girder lines. There also is a 14-ft attached bike trail supported on three lines of girders. The full deck width in each direction is 93 ft 115/8 in. There are another 16 spans that will take the I-74 from Pier 16 to Abutment 32 on the north side of Mississippi Boulevard in Bettendorf. There are seven girder lines taking the 60-ft roadway width (plus variable ramp widths) from Pier 16 to Abutment 32.
Concrete design strengths between 3,500 and 7,500 psi are being employed for various portions of the river crossing structure. Aside from more standard structural concrete mixtures, this project also uses self-consolidating concrete for select portions of the arch ribs and pier columns. The deck over the river (from shore to shore) is 8 in. with a further 2-in. wearing course. North of Iowa’s shore, the deck is uniformly 8 in. thick.
At press time, structural steel for the I-74 crossing was being set on the Illinois shore, which will then expand to meet the Iowa side approaches, as shown here.
On the horizon
“The westbound structure is what we need to open first,” Alvarez said, “so that is where Iowa’s focus is in 2018. The new bridge is finally becoming reality this year. It’s getting easier to see how the bridge will fit into the communities on each side and benefit motorists crossing the river. The new westbound structure is coming along great and construction crews are working day and night to build the substructures in the river.”
Over on the Illinois side, contracts are in their initial stages, but priorities are set and benchmarks for stage completion are looming.
“Our primary focuses this year are to widen I-74 for about 3/4 mile south of Avenue of the Cities and to reconstruct 19th Street,” Ryan Hippen, construction field engineer for the Illinois DOT, told Roads & Bridges. “We’re making significant progress. Both should be completed by the end of this construction season.”
On the Iowa side, recent developments have included setting the first 20-ton steel girders north of the Moline shore; extended pedestal pours for interior piers 12 and 13, which are the arch piers between the two new bridges and will hold two arches each; and the setting of structural steel for span 3 over Grant Street. Moreover, the westbound viaduct deck is now nearly complete.
“What we’re doing is a great improvement for capacity,” said Alvarez. “It’s a really great thing to tie the communities together and really enhance mobility within the Quad Cities.”
Crews pouring the deck for the westbound approach in Bettendorf.