Decades-Long Corridor Trouble Spot Receives Face-Lift
Passing just east of the City of Boone, Iowa Highway 17 is a busy, north-south arterial roadway that connects several rural communities in north-central Iowa. One particular section of the highway with an adjacent at-grade railroad crossing has proven to be a significant trouble spot for many decades. Two critical factors account for many of the problems along this corridor — the proximity of the Union Pacific Railroad yard which results in extensive crossing delays and safety concerns for motorists, and a misaligned section of the highway that causes unnecessary vehicle conflict points and additional railroad track crossings. Snyder & Associates was tasked by the Iowa DOT with performing a realignment study that would also assess the practicality of constructing a grade separation over the UP tracks to alleviate delays and improve safety.
One goal of the realignment study was to evaluate the viability of the project to ensure it’s technically, legally, and economically justifiable. The study also allows for providing stakeholders a clear picture of the proposed project. Our team performed an extensive analysis of the area and developed several alternatives for consideration. To create these viable options, our team took into account the commercial and industrial traffic from the nearby Boone industrial park, as well as the desire to keep business, farm, and residential disruptions to a minimum.
Grade-Separation Overpass Recommended to Minimize Traffic Delays & Increase Safety
The selected project configuration not only separates Iowa Highway 17 vehicle traffic from crossing the Union Pacific Railroad at an at-grade crossing, but it also provides for the closure of two additional crossings. Beginning just north of the US 30 interchange, this extensive project proposes reconstructing and widening approximately ½-mile of Iowa 17. A new 410’, four-span overpass will carry vehicle traffic over 210th Street and the Union Pacific Railroad tracks. To meet the future growth needs of the Union Pacific freight traffic, the bridge was designed to accommodate a third railroad track.
Continuing north from the overpass, a new roadway will be constructed to link up with 200th Street. From there, Iowa 17 will turn east along the existing alignment of 200th Street to intersect at the existing Iowa 17 location. In addition to the new bridge and roadway alignment, S Avenue and 200th Street will both be reconstructed from their current gravel base to pavement to meet the predicted increase in Annual Average Daily Traffic. A new street will also be constructed from the existing 210th Street to serve as the connection between 210th Street and Iowa 17.
Complex Challenges & Practical Solutions
As part of the work carried out by the Snyder & Associates team, the new roadway alignment was created while navigating complex private property obstacles, environmental concerns, and topography hurdles. The remainder of the technical design work included stormwater drainage design, erosion control, and input sessions with the public to receive feedback and address concerns.
The new roadway configuration also required extensive coordination with utility providers in the area. A major ITC Midwest high-voltage transmission line was directly impacted by the realignment and had to be moved. Similarly, numerous gas and water line relocations were required to accommodate the plan.
Snyder & Associates subsidiary, Shuck-Britson, was enlisted to design the overpass bridge. To speed the settlement of the bridge embankments, the design team incorporated the creative use of wick drains, also known as Prefabricated Vertical Drains (PVD). Wick drains act as drainage paths to help divert stormwater from the clayey conditions and consolidate the soil faster. The close collaboration between our team members created an efficient dynamic that helped keep the design process on track.
Understandably, many of the property owners that could potentially be affected by any changes were concerned with how the project would impact their homes, farm operations, and overall land values. To that end, our team held several public engagement sessions preceding design decisions to fully explain the project scope. Our designers listened to the concerns of the public and used that input to guide the design process.
Financial Guidance & Realization of Impact in Action
Funding a transportation project of this expanded scope typically requires numerous sources. The Snyder & Associates team assisted Boone County in applying for and receiving Iowa Clean Air Attainment Program (ICAAP) funding to cover their portion of the project cost. Because the project would also close two railroad crossings, Union Pacific Railroad covered a significant portion of the estimated $14 million project expense.
Snyder & Associates was the primary design consultant on the project, while subsidiary Shuck-Britson provided structural bridge design. The services provided by our firm and sub-consultant team covered every aspect of this extensive project, from preliminary roadway design to management of public participation. When completed, the new roadway alignment is projected to improve traffic safety and reduce vehicle travel times.