Reaching for the Sky

New Air Traffic Control Tower will be Tallest in the Country

by Sheila Bacon

Talk about high-profile.

When the new air traffic control tower at Hartsfield-Jackson International Airport in Atlanta is finished, it will be the nation's tallest. Flanked in 680 precast panels, it represents a sizable concrete job as well.

The 398-ft.-tall tower - scheduled for completion in October 2005, with the Federal Aviation Administration occupying it five months later - will replace the airport's current 232-ft. tower. The existing tower sits in the path of the airport's future international terminal, one part of Hartsfield-Jackson's long-term expansion plans that also include a fifth runway and another terminal.

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Jacksonville-based Gate Precast is the precast subcontractor on the 81,000-sq.-ft. project, casting the panels at its Monroeville, Ala., plant. The panels range in size and shape, with the largest measuring more than 9 ft. tall, 13.5 ft. wide and 3 ft. thick and weighing nearly 49,000 lbs., said Joey Langham, Gate's project manager.

Casting efforts for the tower consumed 20 percent of the Monroeville Plant's capacity, Langham said. Luckily, material for the job was allocated before the current concrete shortage could impact cost and delivery.

Plenty of Panels

The 6,000-psi precast panels define the structural system of the tower's stem. Starting at level four, each 30-ft. level of the stem is made up of 40 panels: 12 outside flat panels, 12 for radius corners panels and 16 interior wall panels. The stem continues up through the cab, which will house air traffic controllers and associated equipment. Steel forms the structural support system for the cab, which is also flanked in architectural precast panels.

Since precast is such a large and crucial part of the job, Gate Precast started working closely with general contractor Hensel Phelps within two weeks of the general's notice to proceed. Six months of meetings, approvals of drawings and panel fabrication preceded the start of precast installation.

Sequencing of work on a job such at this is critical, said operations manager Allan Bliesmer from Hensel Phelps' Dallas, office. If a construction or scheduling glitch occurs in one area of a large office complex, for example, crews can shift gears and continue working on another part of the job. On the ATCT, however, the only way to go is up. If a piece of precast doesn't fit, the entire project is halted.

Fortunately, efforts to keep the job on track paid off.

"Gate has done a tremendous job," Bliesmer said. "They've worked with us on a buildable and aggressive schedule."

Hensel Phelps is no stranger to challenging projects. The general contactor built Orlando International Airport's ATCT - until now, the nation's tallest at 345 ft.

Tower Teamwork

Gate Precast and Precast Erectors of Hurst, Texas, started erecting panels at the Atlanta tower's fourth level March 24, finishing at level 10 before the flare of the cab on June 7 - a pace that could be met only by closely coordinating schedules and working in tandem with the rest of the project team.

Mark Ledkins, Gate vice president of operations, expected complete erection of the tower's precast to be finished in late November or early December - before the originally scheduled date of Dec. 15.

Hensel Phelps crews constructed the first three levels of the tower's stem with poured-in-place concrete, requiring extensive coordination with Gate to ensure a smooth transfer to the precast system. Gate created full-size templates of the cast-in-place building footprint that included all rebar locations so crews could easily blend the two systems.

Both contractors used the carefully drafted templates to design the cast-in-place and precast forms. The transfer went smoothly, despite as little as .25-in. tolerance at the connection points, Langham said.

The stem and cab panels are lightly sandblasted to provide an enhanced surface for paint adhesion.

Gate is the precast subcontractor on two other related structures: a three-story base building at the bottom of the ATCT, which will house offices, administration space and the tower's mechanical and electrical services, and a one-story engine generation building housing emergency power. Gate subbed out the precast work for a 120-vehicle parking structure for FAA employees.

Hensel Phelps is the general contractor on all three projects.

Project Team:
Owner: City of Atlanta's Department of Aviation
General Contractor: Hensel Phelps Construction Co., Orlando
Precast Subcontractor: Gate Precast, Jacksonville, Fla.
Erection Subcontractor: Precast Erectors, Hurst, Texas

Useful Sources:

For more information on other projects under way at the airport in support of the fifth runway can be found by visiting the following:

http://www.atlanta-airport.com/default.asp?url=http://www.atlanta-airport.com/sublevels/airport_info/fifth.htm