January 18, 2022

When traveling through O'Hare International Airport (ORD), the general public may not realize that getting to their destination within Terminals 1, 2 or 3 via the Elevated Parking Structure, Surface Lot C, the Hilton Hotel and even the CTA Blue Line requires you to walk through one of seven pedestrian tunnels. These access points are located underneath the Terminal lower Level Roadways and were constructed in 1977 of cast-in-place reinforced concrete varying in lengths. The interior of the tunnels were originally lined with terrazzo finishes, tile walls and drop ceilings. In between the drop ceilings and the tunnel top are infrastructure utilities, and in between the tunnel top and lower level roadway subgrade, are general site utilities for storm, sanitary, water, and electrical.

Over the last decade, the existing tunnels experienced significant leaks during heavy rain events. This fact resulted in repeated maintenance, drying and cleaning of the interiors spaces, and, on occasion, the temporary closing of a tunnel by the Chicago Department of Aviation (CDA). The toll of the leakage over time also caused damage to the interior finishes. Past attempted localized repairs were not fully effective; therefore the CDA made the decision to implement a permanent and long-lasting solution.

Initially, Epstein's civil engineers were tasked with evaluating the existing conditions of the seven Pedestrian Tunnels to determine the source of water infiltration, and provide recommendations to remediate the infiltration. The scope of that work consisted of:

  • 3D laser scanning surveys of the interiors of each tunnel
  • Creating a 3D BIM model in Autodesk Revit of each of the tunnels
  • Analyzing the existing groundwater conditions in the adjacent areas of each of the tunnels
  • Investigating the potential source of water infiltration
  • Developing remediation options with preferred solutions
  • Creating a sample test area for the polyurethane injection
  • Providing construction documents for the selected remediation options
  • Providing Construction Phase Services

These design improvements consisted of:

  • Lining of existing storm sewers systems affecting the tunnels
  • Replacing failed or collapsed storm sewers systems affecting the tunnels
  • Replacing deteriorated sidewalk surfaces in the Terminal areas affecting the tunnels
  • Removing tunnel architectural wall and ceiling finishes
  • Conducting structural inspection of the walls, and floors
  • Injecting polyurethane to provide soil densification outside of the tunnel walls
  • Repairing concrete walls and ceilings
  • Replacing all tunnel expansion joints
  • Replacing existing architectural finishes and architectural renovation of all pedestrian tunnels

In addition, Epstein's interior architects and engineers were then selected by the CDA to design a complete interior renovation of the Pedestrian Tunnels in conjunction with the Water Infiltration Remediation project that was already in progress by Epstein's civil engineers.


The project construction was phased, resulting in a situation where the water infiltration remediation and the interior renovation projects were highly integrated, said Laura Rebbe, AIA, LEED AP BD+C, Epstein's Vice President and Project Manager. Because of this, both projects were permitted and released for bid as one single project.

For the architectural design of the tunnels, Epstein's interior architects conducted several charrette sessions with the CDA to finalize the concept. The inspiration was Chicago a city that is vibrant, continuously changing, modern, but with a rich history, and a leader of the sustainable movement in the U.S. Additionally, the theme of each tunnel followed the same color scheme of the terminals they are leading to. As such, Terminal 1 features blue gradient wallpaper and images of the Chicago skyline, lake, river and flag; Terminal 2 features orange gradient wallpaper with images from the Chicago Theater District; and Terminal 3 features green gradient wallpaper with images from Chicago parks and green roofs.

The design intent focused on several approaches.

Epstein's design team eliminated the inherent symmetry of the tunnel by creating an asymmetrical design. We accomplished this by extending the equally-spaced metal panels past the center of the tunnel while creating a higher ceiling. Furthermore, the lighting scheme supports this design by introducing pendant fixtures in between the metal panels and using a linear fixture on the opposite side.

The asymmetrical design also creates a passive side and an active side. The active side features curved corrugated metal panels and pendant lighting fixtures, while the passive side has a continuous wood finished wall surface with linear lights and a lower ceiling.

Finally, the Epstein design team broke up the linearity by introducing LED screen areas at regular intervals in every tunnel. Each features a different floor finish pattern as well as a different lighting scheme.

In addition to Epstein's design services, the interior renovation scope also includes:

  • Developing energy efficient and effective lighting concepts and systems
  • Modifying and upgrading the mechanical system serving the project area

These tunnels are the primary connection arteries for passengers and public arriving by the CTA Blue Line or parking in the garage, as well as guests of the O'Hare Hilton. The previous tunnel space was a very uninviting welcome to O'Hare, Laura said. This project put an end to the CDAs constant maintenance of these areas, with regard to water infiltration. Of equal importance, this project also provides the airport with a beautiful, welcoming first impression for the traveling public!

Lastly, this project is a grand example of the unique services and capabilities of Epstein, highlighting our engineering acumen at determining and solving a vexing water infiltration issue, as well as our design talent at taking a dark and utilitarian piece of infrastructure and re-imaging it as a new and vibrant public access space.