Terminals 2 and 3 Air-handling Unit Replacement at
O'Hare International Airport

Project of The Year: Industrial

Forty-two air-handling units have been replaced in terminals 2 and 3 at O'Hare International Airport in Chicago.

The project also included the replacement and-or modification of the city's electrical switchgear, installation of new motor control centers and installation of supporting electrical services for the new equipment and existing equipment.

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The fire protection sprinkler system was added in terminals 2 and 3 penthouses. During the phased demolition and reconstruction of the penthouse air handling unit systems, a temporary air handling system that included cooling, heating and electrical power was also provided.

Had Old Equipment

The work involved replacing existing penthouse HVAC equipment that was originally installed in the 1960s.

The mechanical equipment rooms were congested, poorly illuminated and did not allow adequate access for equipment/systems maintenance. Existing structures were so aged that common tasks required special care to prevent the infiltration of noise and water to public areas.

The project had several requirements.

Airlines and airport operations could not be affected, and all existing services were to remain completely operational so that airport users were unaware of the renovation other than what could be seen on the roof.

System quality that was equal to or better than existing systems was to be provided.

Coordination was necessary with other Department of Aviation and airline construction projects in progress in preparation for O'Hare's expansion.

The new systems were oversized in terms of physical size and capacity to accommodate future terminal expansion. The points of connection between new and existing systems occasionally conflicted in terms of size, type and orientation.

The equipment was hoisted using operational aircraft gates as crane and truck staging areas, and day-to-day coordination was required between the contractors, airlines, control tower personnel and Department of Aviation staff.

Full security screening was applied to workers, materials, equipment and trucks.

Temporary System Installed

A temporary HVAC system was installed that provided year-round climate control to all spaces with systems out of service due to the project.

The temporary system included the installation of two 250-ton, 50,000-cu.-ft.-per-minute rooftop units.

They were put on a temporary steel structure constructed on the penthouse roof. The units were located on opposite ends of the structured and connected by a 72-in.-dia., double wall spiral duct system.

Temporary supply and return ducts connected the spiral system to existing zone duct penetrations at the penthouse floor and allowed for demolition of the penthouse area for each phase of work.

The orientation of the replacement air-handling units created logistical conflicts.

Originally, demolition and replacement of two air-handling units on opposite ends of the penthouse was the goal. The related mechanical, electrical and plumbing systems crossed over or under new or existing work.

This resulted in physical limitations that created numerous construction, operation and maintenance issues.

An alternative plan was developed that consolidated the scope of work that allowed for simultaneous demolition and replacement of five to six air-handling units per phase. This resulted in savings of $225,000 and 90 days of work.

Physical space was limited, yet five to six new air handling units that were 12-by-25-ft. each, related equipment and up to 80-person crews were to be accommodated in an area that was about 6,000 sq. ft. Staggered start times, shift work and weekend work allowed individual trade crews to concentrate on their respective tasks in sequence.

The Department of Aviation wanted to tie the existing campus temperature control system monitoring into a new open-protocol temperature control system, and the new BacNET open-control temperature was installed.

The jury said, "The issues of dealing with the city of Chicago's bureaucracy are always extensive, yet this project was delivered 90 days early. The project was on a 24-hour/seven-day-a-week schedule. It was diabolically challenging.

That it was done on time was a miracle."