Gulfport-Biloxi Int'l Fixes Deteriorating Touchdown Zones

Despite extra challenges from a mid-project military event and an unusually large pool of stakeholders, Gulfport-Biloxi International Airport (GPT) finished a $13.6 million runway reconstruction project last year - on time, on budget and without any interruptions to commercial airline service.

The main component of the project was replacing two deteriorating touchdown zones on the airport's concrete primary runway - a 2,000-foot section on the northwest end and 1,500 feet on the southeast end. At 9,002 feet long, and 150 feet wide, Runway 14-32 accommodates commercial airliners, heavy cargo planes and military aircraft. GPT's other 4,935-foot runway handles only general aviation traffic, because it's too short for commercial traffic. 

"It was a very complicated project with a lot of moving parts," reflects Jim Foster, assistant executive director for the Mississippi airport. "A lot of people came together to make it happen."

During the project, work crews:
  • removed roughly 18,000 cubic yards of concrete;
  • repaired 22,000 feet of runway joints and cracks;
  • hauled in 14,000 cubic yards of soil to re-grade the runway safety area;
  • installed about 19,000 cubic yards of new concrete; and 
  • applied 315,000 square feet of new runway markings. 

"There were so many critical points where had something gone wrong, it would have thrown us off our timeline and interrupted airline operations," Foster recalls. "But in the end, we experienced no flight delays. We opened up the runway on time every day."

Team members from Neel-Schaffer, the engineering company that designed and coordinated the project, recall the effort it took to pull that off. "It was one of the most complicated projects we've ever worked on, in terms of the logistics involved with doing the work and keeping the airport running at the same time," says Kreg Overstreet, the company's senior project manager.

The airport maintains schedules with four major airlines and served more than 662,000 passengers last year. It's also home to the Air National Guard Combat Readiness Training Center and the Mississippi Army National Guard 1108th Theater Aviation Sustainment Maintenance Group. 

As such, the military paid for $6.6 million of the project, which covered all costs for two new aircraft arresting systems and 43% of the runway reconstruction. (Research showed that military aircraft account for 43% of the runway's annual traffic.) A grant from the FAA Airport Improvement Program funded the remainder of the project, with GPT footing 10% of that portion, Foster reports.

Lots of Moving Parts

The magnitude and complexity of the project's original scope ramped up considerably during the planning stages. For starters, discussions with the Air National Guard revealed that the military planned to upgrade the runway's two aircraft-arresting systems to meet updated safety requirements. Waiting to do that work would have meant displacing the thresholds as well as tearing up and reinstalling the concrete in the touchdown zones, so it made more financial sense to do both projects simultaneously.

"Combining the projects killed two birds with one stone," Foster explains. "Replacing the arresting systems as a stand-alone project would have required doing all this coordination between agencies twice. It would've doubled the complications, and cost more, too."

Further complicating matters, the Air National Guard was holding a large-scale operations exercise October 27 to November 7 - near the middle of the project's timeline. The event would include more than 51 military units from 23 states and one allied nation, including a large number of aircraft that engage in simulated warfare operations. Given the huge economic benefit that the annual Operation Southern Strike brings to the surrounding region and GPT, it was critical to phase the project so a full-length runway was available during that 11-day span, Foster explains.

Another challenging factor was the large contingent of stakeholders involved. GPT, the Air National Guard, commercial airlines, general aviation tenants, contractors and about a half-dozen offices and divisions of the FAA had to communicate and cooperate to make the multi-phase initiative possible. 

Changing the runway grades to bring them into compliance with FAA regulations introduced yet another project element: upgrading the medium-intensity approach lighting system.

Foster knew it was crucial to move quickly, because the FAA normally programs projects of this magnitude three to five years in advance. "The key was starting early," he recalls. "From the time we identified what the problem was, we had well over a year of planning before we bid the project and got the funding lined up - and coordinated with the FAA, the airlines, general aviation tenants and the military."

In retrospect, Foster says that getting ample lead on the project and planning it in phases were critical factors to success. So was sticking to the plan.

"This is the first time I've seen a plan follow the timeframes laid out with minimal problems," he reflects. "Issues always crop up in major projects; but this one was well thought out. We stuck to the plan and got it done on time."

Foster also notes the value of partnering with an engineering firm that was knowledgeable about GPT, hiring contractors that had specific experience with airport projects and maintaining good communications with all the stakeholders.

Problem Areas

Deteriorating concrete in the main runway's touchdown zones, which were about 15 years old, spurred the project. Airport operations personnel first noticed the problem in early 2012, when a slight hump appeared in each touchdown zone, where the asphalt and concrete sections abutted. "We thought it was a construction defect with the way the joint was designed," Foster recalls.

Actually, a condition called alkali-aggregate reactivity - a chemical reaction between the aggregate and the highly alkaline cement used to make the concrete - caused the problem. The reaction causes the concrete to expand, which eventually leads to cracking and spalling. While both results are negative, the latter generates unacceptable levels of debris on runways, Overstreet notes. 

"When the concrete touchdown zones were installed around 1999, no one knew this was a problem," Foster explains. "But we've come to find out that this problem has occurred at airports all over the country. Now, they test aggregate to make sure it will not react."

After considering six strategies for resolving the problem, project stakeholders agreed that a two-step plan would be the most cost-effective and least-disruptive option. First, GPT would temporarily extend the available runway length by rehabilitating 14-32's two 1,000-foot-long overrun sections, which were in poor condition and no longer met FAA safety standards. Contractors would perform as much work as possible at night to minimize disruptions. Typically, commercial flights landed before 11 p.m.; but if any arrived later, contractors had to wait to start working.

To hold costs down, the temporary overruns were installed with a thinner concrete section, designed to support aircraft operations projected for the 143-day project vs. a longer typical lifespan. After construction, the paved overruns were left in place to serve as an extended runway safety area. "Since we were replacing the touchdown zones, we decided to upgrade our overruns at the same time," Foster explains. "Had we decided to do that in a different year, we would have had to displace the end of the thresholds again."

The selected option also allowed the airport to maximize available runway length - which varied from 7,000 to 7,500 feet during the project - through the use of declared distances for commercial takeoffs and landings on the runway. (Declared distances allow airlines to calculate the baggage and passenger restrictions required to enable safe takeoffs and landings on shorter runways.)

Temporary navigational aids were required during phases when a runway threshold was displaced. Commercial airlines require some form of vertical guidance in order to use the runway. Because the glide slope antennas were temporarily decommissioned during construction, the airport used temporary precision approach path indicators to provide vertical guidance.

Step By Step

Planned in six phases, the project ran from mid-July to mid-December. Daily coordination among all the affected parties was required to stay on schedule; for the most part, work progressed without a hitch, Foster reports. The biggest hiccup occurred when crews pulled up more asphalt sub-base than expected while removing the runway's nearly 1-foot-thick concrete. "But we reworked things on the fly and dealt with it," Overstreet relates. "We ended up putting down more econocrete, which is a lean concrete used as a leveling course."

Overstreet praises the cooperation exhibited by all the parties involved with GPT's runway renovation, noting that when large projects like it unravel, an uncooperative team member is usually the culprit. "If you don't have everyone pulling together ... it can wreck the whole show," he notes. "From the airport, R.C. Construction (the primary paving contractor) and the Air National Guard to the airlines, the general aviation tenants and the FAA, everyone worked together. That's the number one reason we were able to keep this thing moving and finish on time and on budget."

Another key to success: effective communications across-the-board. "With as much communication as we had and as much planning as we did, you can always do even more communicating," he reflects. "You need to communicate as much as you can and as often as you can to as many people as you can - make sure everyone is in the loop."

While Forster acknowledges that the project was stressful, he also considers it a great experience. "My old boss said you should only have to do something like this once in a career," he says. "It's the kind of thing that's really a challenge, but by the time it's finished, you're glad you were able to participate in it. It's always great to overcome a good challenge."