Iowa DOT Achieves Major Milestone During Construction of Dual, Divided Freeway in Council Bluffs
A First for Southwest Iowa: Council Bluffs Moves Closer to Easing Congestion by Completing Region’s First-Ever Dual, Divided Freeway
In southwest Iowa, motorists are now able to access a section of the region’s first-ever dual, divided freeway (DDF). This modern freeway system is being constructed on the south side of Council Bluffs, along the overlapping section of Interstate 80 and Interstate 29, as a way to improve safety and mobility for those traveling through the area. The DDF physically separates through traffic on I-80 from traffic on I-29 destined for Council Bluffs, creating I-80 express lanes and I-80/I-29 local lanes.
Open since March, the reconstructed lanes on westbound I-80 and northbound I-29 span three miles between the East and West System interchanges. Westbound motorists on the three local outside lanes will be able to exit at various points while vehicles traversing the three inside express lanes can enjoy minimal interruptions during their highway cruising.
The DDF design is intended to reduce crashes and other issues caused by merging traffic between tightly spaced interchanges. Once the system is fully operational, it is projected to reduce annual crashes by as much as 21 percent and fatal and injury crashes by 18 percent.
“The dual, divided freeway will be a big change for drivers in the region,” says Scott Schram, Iowa DOT District 4 Engineer. “However, the growing pains of change will be worth it in the long run because this will improve safety and ease congestion.”
The $125 million highway overhaul is an eight-year-undertaking that began phased construction in July 2013. HDR is serving as the project’s program manager and general engineering consultant, and is also assisting Iowa DOT with design engineering. Geotechnical engineering support is coming from Terracon and Jacobs. Thus far, three of four construction contracts have been awarded – two to Hawkins Construction Company and one to Peterson Contractors, Inc.
A Project of Necessity
For over a decade, the Iowa Department of Transportation has been working to reconstruct I-80, I-29, and I-480 in the Omaha-Council Bluffs metropolitan area. Originally built in the 1960s, the outdated design of these high-traffic corridors require modernization to keep pace with future population demands.
The I-80/I-29 project is a key component of a comprehensive interstate redesign known as the Council Bluffs Interstate System Improvement Program. The $1.6 billion program, which began construction in 2008, aims to modernize 18 miles of mainline interstate highway and 15 interchanges by 2024.
Overview of the I-80/I-29 Overhaul
The DDF construction scope consists of building four separate roadways – two roadways for traffic in each direction. Three lanes in each direction will be dedicated for I-80 Express and three lanes in each direction for I-29/I-80 Local. The 12-foot-wide lanes are to be separated by a concrete median barrier, along with 10-foot-wide shoulders with an additional 2 feet of clear distance to the barrier railings.
To construct the roadway, workers first laid 12 inches of special backfill comprised of granular materials on top of the earth subgrade, then placed a 6-inch layer of drainable granular subbase. After compaction of the materials, crews poured 11 1/2 inches of Portland cement concrete pavement.
“Most of the pavement was constructed with paving equipment using GPS paving control systems instead of the traditional string-line setup,” adds Schram. “The pavement transverse joints are reinforced with 1 1/2 inches of smooth epoxy-coated dowel bars and the longitudinal joints are reinforced with #5 deformed epoxy-coated rebar. A 4-inch subdrain is used under the pavement to collect water within the drainable granular subbase and carry it to the storm sewer intakes.”
The project corridor’s sandy subsoils can retain a great deal of moisture due to a high water-table. This is due to the area’s proximity to the Missouri River, which is bordered by extensive wetlands and deciduous forest. Consequently, earthwork and geotechnical issues have posed considerable project challenges. To minimize settling times and control the overall schedule, lightweight foam concrete and wick drains have been implemented.
In late 2018, workers substantially completed the second phase of construction. This project segment included three new bridges and a new 24th Street exit for I-80 eastbound travelers. The construction crews also fully rebuilt the I-29 southbound/I-80 eastbound local lanes spanning between the Missouri River Bridge to just east of Indian Creek. At the completion, five total lanes were opened for eastbound I-80 traffic just west of the Missouri River Bridge, easing congestion on this bridge linking Iowa to Nebraska. The I-80 eastbound traffic now connects to I-80 express lanes before gradually merging back into existing conditions east of the 24th Street interchange.
The I-80/I-29 highway improvement project will enter its third and final phase in August. The DDF’s eastbound I-80/southbound I-29 segment – located between the 24th Street interchange and the East System Interchange – is expected to open in Fall 2019. The entire project is expected to wrap up by June 2021.
“Maintaining traffic in this busy corridor is a challenge,” Schram comments. “Building in the clear and shifting traffic to new pavement when it’s complete are among the solutions to this obstacle. We also have to minimize ramp closures and impacts to businesses.”
State transportation planners chose a DDF design over simply widening the interstate for three key reasons: it offers greater flexibility to travelers, it effectively mitigates traffic congestion, and it is proven to boost the safety and efficiency of transportation networks.
Traffic flow can be hampered not only by congested exits, but also by lane closures caused by crashes or road maintenance. On a DDF, traffic is kept lighter due to the separation of express and local lanes because the usual merges and exits are more spread out. This separation helps reduce the usual rush-hour pileup or holiday traffic jams that typically occur. The barriers between all roadways are also built with breaks and gates, which provides access to emergency personnel vehicles and allows traffic to be shifted to different lanes if an accident does occur.
Other roadway elements will support the state’s goal of enhancing traveling safety for motorists.
These include color dynamic message signs to assist with emergency notices and wayfinding, and overhead guide signs to aid traffic navigation. In addition, interchange areas will be illuminated by high-mast tower lighting while the medians between the local and express lanes will be brightened by energy-efficient LED luminaires.
The project also aims to accommodate future traffic growth and planned development in the area. Noteworthy landmarks along the I-80/I-29 corridor in Council Bluffs already include the Mid-America Center (the region’s premier entertainment and convention center) as well as the Western Historic Trails Center, the Westfair Amphitheatre, and the Council Bluffs Recreation Complex. Travelers also use this thoroughfare to access a variety of shopping centers, casinos, hotels, restaurants, truck stops, gas stations, and more.
According to project officials, planned development in the region includes expansion of the River’s Edge Pavilion at Tom Hanafan River’s Edge Park, construction of a new Google Data Center in the Omaha area, and the addition of a new wellness center at Iowa Western Community College. Also, transportation planners project significant residential growth occurring at the east end of the Council Bluffs area and the surrounding rural communities in the years to come.
The Omaha-Council Bluffs metropolitan community has much to look forward to as the I-80/I-29 dual, divided freeway project draws closer to completion. While these highway improvements are vital to supporting the region’s continued population growth and economic demands, most importantly, they fulfill the state’s mission to promote traveling safety, efficiency, and convenience.
Photos courtesy of the Iowa Department of Transportation