Phase 1a Extension

Built by a joint venture between the Tempe, Ariz., office of McCarthy Building Cos. and the Phoenix office of Kiewit Corp. under a construction manager at-risk contract, the Phase 1a extension will be supported by 55 caissons at depths of 60 to 125 ft. Crews will demolish several small buildings and perform extensive potholing to ensure the extensive site utilities and old foundations are accounted for, says Mason Williams, McCarthy-Kiewit JV deputy project manager.

Two existing taxiways need to be extended by 80 ft to allow the new guideway to pass underneath. Each taxiway will be demolished, excavated and rebuilt separately, each under a tight six-month time constraint to prevent any delays to air traffic and to ensure both aren't closed at any one time. In addition, the first taxiway needs to reopen by November before the second is begun so that both taxiways are open for the busy holiday travel season, Kotchou says.

"Once we get the substructure up with the two abutments, we will backfill and pour a waste slab to build the bridge extension on soffit dirt to accelerate the construction process, instead of doing the traditional method of digging the whole thing out and doing falsework," Williams says. Once the new structure is tied in with the existing taxiway, crews will excavate the temporary dirt to release the new bridge extension.

The new guideway will tie into an existing abutment from the first phase, to continue a 6% grade descent to about 30 ft below taxiway level, parallel to an existing roadway. Once past the taxiways, the guideway rises 40 ft above grade to pass over the passenger concourse. Since the terminal is open 24 hours, construction of the track over the gate connector can only occur in brief three-hour windows each night.

High Security

The entire new length of track runs parallel to an active runway and taxiway, so timing and sequencing of work is essential. "The closure of a taxiway or any interruption to airport operations requires a higher level of communication beyond just scheduling the work—it must also be integrated with ongoing airside operations," says Dennis Tucker, McCarthy vice president.

Every construction worker has to submit to a background check before being issued an ID badge, and is bussed in each day to specific security checkpoint gates to access the jobsite. If there's an emergency, they can't call 911—the airport has its own rescue station. Fortunately, the job has had zero incidents or recordables to date, says Joseph Brunsman, McCarthy-Kiewit project manager. The project will see 300 to 350 workers on site at peak.

The airport allowed the taxiway S construction zone to temporarily become 'land-side', meaning outside of the high security area. "it's a more efficient way to construct at an airport, saving time and most likely money," Kotchou says. A perimeter fence approved by FAA security was erected around the entire taxiway construction zone.

The City of Phoenix mandates LEED certification when the project opens in early 2015. Sustainable efforts include the use of certified wood products, separating trash and the use of building materials incorporating recycled content. These efforts, along with recycling concrete and asphalt from the demolition as fill, has helped the team reach the cusp of LEED-Gold, Brunsman says. The site is situated on an old river bed, so excavated cobble is also being crushed on site for reuse as fill.