The Iowa DOT is leading a $163.6 million project to widen I-35 by adding new lanes, bridges, and interchanges for a safer and more reliable travel experience. The construction will address heavy traffic and weather challenges, aiming to improve infrastructure for better connectivity and competitiveness.
Photo courtesy of Vern Benson, Iowa DOT
The Iowa Department of Transportation (Iowa DOT) is overseeing a $163.6 million project that will widen I-35 from four to six lanes for 9 mi. between Ankeny and Huxley.
The Iowa Department of Transportation (Iowa DOT) is overseeing a $163.6 million project that will widen I-35 from four to six lanes for 9 mi. between Ankeny and Huxley. Construction includes building five new bridges, including two interchanges.
"Once construction is complete, this corridor will be a much safer route, with the increased capacity, full width paved shoulders and the wider median between the lanes," explained Scott Nixon, Iowa DOT construction engineer. "Some additional safety improvements are being made at the two reconstructed interchanges. They include new ramps with improved geometric features; improved sight distances entering the side roads; and turn lanes for side road traffic entering the interchange ramps."
The construction also will improve travel reliability.
"Iowa DOT plans to add a third lane of traffic in both directions between Ankeny and Ames, which will reduce maintenance and congestion," said Nixon. "The first phase of this project involves adding three lanes from Ankeny to just north of Huxley. The initial bridge project began at the Elkhart interchange, with new pavement built on I-35 southbound 36th Street north to NW 134th Avenue."
Photo courtesy of Kory Vorwald, C.J. Moyna and Sons LLC
This section of Interstate 35 currently carries an average of 53,000 vehicles per day and is expected to increase to 103,000 vehicles per day by 2045. The current four-lane corridor is one of the heaviest traveled four-lane sections of roadway in the state.
According to Nixon, motorists can expect to see intermittent nighttime lane closures for the duration of the project, as well as complete closures occurring periodically for bridge beam setting. During the daytime hours of travel, commuters will experience several lane shifts and temporary barrier rail with reduced shoulder widths throughout the project.
Nixon noted that constructing multiple bridges and two interchanges is a major undertaking.
"The corridor was divided in half, due to the size and scope of the work involved in the reconstruction. The bridge subcontractor for both contracts is United Contractors Inc. and Subsidiaries from Johnston, Iowa. They have had multiple crews working day and night to remove existing bridges and construct new ones.
"We limited when certain bridges could be removed in the staging of the projects, so that local traffic could continue to travel to either side of the interstate during construction. This has required the contractors to perform the work within tight time frames to allow all the work to be completed within the number of working days on the contracts."
Nixon explained the main construction challenges involve dealing with motorists and the elements.
"Traffic on I-35 is very heavy, particularly during the morning and evening commute times. Material deliveries to the site must be done from side roads during off-peak hours. Any lane closures required on the mainline of I-35 are required to be done at night. During bridge demolition, both directions of I-35 were completely closed, and traffic detoured. This occurred for two nights during the demolition of the existing bridge, and for two nights for the setting of the beams on the new bridge being constructed this year.
"Like anywhere in the Midwest the weather is always a factor. This spring and early summer we experienced numerous rain events and even had a tornado go through the project, which took out a major electrical transmission line that parallels I-35."
Currently, grading contractor and prime C.J. Moyna and Sons is working on grading the new ramps at an interchange that will be fully reconstructed next year on this project. A portion of the new ramps are outside the footprint of the existing interchange, and crews are working on portions that do not affect traffic.
The interchange is required to remain open until the spring of 2025 due to other Iowa DOT projects in the area. In addition, the bridge subcontractor, United Contractors Inc., is placing reinforcing steel on the deck of the new bridge over I-35 and pouring the deck.
Most of the drainage structure work has been completed, as well as a majority of the grading that can be performed this year. A major item of work already finished is the construction of a new reinforced concrete box culvert that will serve as a pedestrian tunnel under I-35 on the Heart of Iowa Nature Trail.
"The trail is on an old railroad bed, and the tunnel was constructed under the bridges that carry I-35 over the trail," said Nixon. "Once traffic is switched from the existing lanes onto the new southbound lanes, the existing bridges will be removed, and grading will be done over the trail tunnel and new lanes will be paved on the new grade."
Crews have yet to pave the new southbound lanes. The paving subcontractor, Flynn Company Inc. of Dubuque, Iowa, placed granular subbase material on the finished grade and then began PCC paving. The goal is to have as much paving completed this year as possible and get traffic onto the new southbound lanes by mid-year in 2025.
Project milestones have included completion of the culvert extensions, pipe extensions and the trail tunnel, so that grading work could commence. A significant event will occur next spring, when the contractor is able to close the interchange with Iowa Highway 210 and start reconstructing the ramps and overhead bridge.
Another major milestone that will occur next year is getting traffic on the new southbound lanes. This must take place so the contractor can remove the existing southbound lanes and start constructing additional lanes adjacent to the new southbound lanes for northbound traffic to be staged during the northbound reconstruction project, which will start in 2026.
To construct the new bridge at 315th over I-35, the contractor was required to build temporary detour pavement in the existing median between the existing southbound and northbound lanes. This was necessary due to the new center pier of the bridge being in the existing southbound lanes. The work called for many nighttime lane closures for grading the median and paving the detour. Once traffic was switched, the bridge contractor had full access to the center pier and was able to begin construction.
Ryan Kipp, vice president of CJ Moyna & Sons, said a number of steps are involved when building a new structure.
"They include installing temporary pavement to shift southbound I-35 traffic to allow the construction of the median pier. Grading the berms on the east and west side of I-35 also is necessary, along with constructing the bridge abutments, setting PCC beams, installing formwork, installing reinforcing steel, pouring the PCC deck, constructing concrete barrier rail and bridge approach pavement."
Kipp noted that construction of five bridges, including two new interchanges, must be carefully choreographed.
Photo courtesy of Kory Vorwald, C.J. Moyna and Sons LLC
"Bridge work is scheduled to coincide with the Iowa weather. The larger concrete pours were scheduled to avoid the cold winter months. Multiple crews are dedicated to the project to ensure work is completed in a timely manner. A schedule that accounts for grading, bridge construction, paving, etc. is developed at the beginning of the project to identify the critical milestones that need to be achieved to ensure the project continues to move forward."
The grading work on the entire corridor consists of 1.75 million cu. yds. of earthwork, and 238,000 cu. yds. of topsoil. Equipment required includes Mobile Track Solutions and Caterpillar earthmoving equipment; KPI-JCI aggregate crushing equipment; Guntert & Zimmerman and GOMACO PCC paving equipment; Link-Belt lattice crawler cranes; and Mack trucks with side dump trailers for on-road hauling.
Regarding materials being used, said Kipp, "The majority of the pavement is being processed and crushed for re-use as aggregate subbase on the project. There also is a large amount of concrete and steel reinforcing being placed for PCC paving, RCB construction and bridge construction. Asphalt is being used as temporary pavement, and the installation of concrete and steel pipe is necessary for drainage."
As work continues on the project, Kipp said having the opportunity to serve motorists in the area is a privilege.
"It's exciting to partner with Iowa DOT to construct the infrastructure to benefit Iowa and the entire United States. I-35 is a major north-south corridor to move goods throughout North America. We understand the important role that infrastructure plays to ensure that Iowa and the U.S. remain competitive in the global marketplace." CEG
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