Project Case Study: Safer safety zones

March 2006 » Feature Articles
Environmental conditions at busy general aviation, commercial, and military airports directly affect operational safety and efficiency. For example, groundcover in the safe zone areas surrounding runways and taxiways influences factors such as aircraft damage caused by wildlife and foreign objects, water drainage, soil erosion, maintenance operations, and emergency response.

Artificial turf eliminates foreign object damage, drainage, maintenance, and emergency response problems on airport runways and taxiways.

BY JOE DOBSON

Project
Improvement of airport safe zone areas

Product application
Replacing infield grass with artificial turf from Air FieldTurf controls environmental conditions to improve airport safety and operations.

Environmental conditions at busy general aviation, commercial, and military airports directly affect operational safety and efficiency. For example, groundcover in the safe zone areas surrounding runways and taxiways influences factors such as aircraft damage caused by wildlife and foreign objects, water drainage, soil erosion, maintenance operations, and emergency response. To address these problems, projects at several major airports, including Boston Logan International and Honolulu International, installed sections of artificial turf as an alternative to natural vegetation, asphalt, or concrete.

Foreign object damage control-As airports grapple with foreign object damage (FOD) control, they seek effective ways to keep the debris and wildlife off of runways and taxiways. For example, Honolulu International Airport experienced shutdowns of a particular runway every time a large aircraft taxied by. The site contained large amounts of loose coral and a jet's engine exhaust would scatter the coral onto the runway and taxiway. This was deemed a major FOD hazard and the airport consistently faced the expense and challenge of closing the taxiway to perform proper cleanup. In June 2003, the airport's personnel installed an artificial turf called Air FieldTurf, which eliminated the problem.

Another FOD-control problem arises because the natural vegetation that surrounds many runways creates an environment that attracts birds and wildlife. According to the Federal Aviation Administration (FAA), aircraft wildlife strikes are a serious cause of aviation-related accidents and fatalities. Between 1990 and 2004, there were more than 59,000 wildlife strikes to commercial and military aircraft. Use of artificial turf in place of natural vegetation creates a ┬ôsterile┬” environment in the safe zones of runways and taxiways by eliminating food sources and natural habitats, which deters FOD caused by animals and birds.

Water drainage and soil erosion-Ponding of water is not a welcome sight to those who maintain and use an airport's infield.

After a heavy rain, soil on runway and taxiway shoulders can become saturated and leave standing water. Ponding of water is a potential hazard for transiting aircraft because it may cause hydroplaning, which can cause an accident or serious damage.

When artificial turf is installed on a properly prepared sub-base, water percolates through it and is quickly gone. For example, Air FieldTurf permeable turf percolates at a rate of 60 gallons per square foot per hour. In an FAA test of Air FieldTurf 's drainage characteristics, pooled water penetrated through in 2 to 3 minutes, and was completely gone within 5 minutes. After 30 minutes, the area was dry to the touch.

At Boston Logan International Airport, 9,000 square feet of Air FieldTurf was installed on a prepared base in a taxiway safety area that had experienced significant erosion problems. Boston Logan chose Air FieldTurf because of its drainage characteristics and its ability to be installed on top of a prepared subgrade. The artificial turf ultimately alleviated the problems of rutting, drainage, and erosion and did not require alterations or additions to the airport's stormwater drainage system or subgrade.

Airport maintenance-Closure of operational areas is required for mowing and care of natural surfaces. Often, grass cutting is performed during night shifts when air traffic is suspended. But in the low-light conditions, maintenance workers often drive mowing equipment over runway light cans and knock down navigational signs. Another problem that occurs with traditional groundcover is that, if the soil is soaked and not amenable to mowing, the task must wait-and the grass gets higher and exceeds FAA regulations. Artificial turf obviously alleviates all of these maintenance costs and challenges.

Emergency response-To determine how well artificial turf would perform if an infield accident occurred, causing fire in the safety area, experts at the FAA's William J. Hughes Technical Center thoroughly tested Air FieldTurf in simulated fire, heat, and smoke scenarios. The top 1/2 inch of the 2-inch turf fiber was exposed and was doused with various flammable liquids, including JP-8, which has a very low flashpoint. Test conditions were unable to cause the turf to act as an accelerant-even in the presence of 10-mph winds. The exposed top fibers melted instantaneously, yet only down to the layer of the sand infill. The sand acted as a barrier or oxygen snuffer. It absorbed the jet fuel, removed the oxygen content, and broke the fire triangle. Its quick burnout was notable, but also of importance was its quick drainage of water out of and away from the turf surface.

Turf composition and installation

Artificial turf is made from polyethylene fiber that is 120 microns thick. The turf is produced with a depth of approximately 2 to 2-1/2 inches and held in place with approximately 1 inch of silica sand infill, which is brushed into the turf to firmly ballast and anchor the turf system to the surface it covers.

Installation of artificial turf normally should be accomplished during an airport's overnight shift. The subgrade may be prepared to be a load-bearing or a non-load bearing base. The turf also may be specified as permeable or non-permeable, depending upon the site's drainage requirements.

Installation procedures vary according to manufacturer specifications.

For example, Air FieldTurf is first anchored to a 6-inch by 6-inch curbing made from recycled plastic, which abuts against the runway's or taxiway's asphalt shoulder. This curbing is anchored with 16-inch-long by 5/8-inch-diameter steel rebar and has a 2- inch by 1-inch notched recession. The turf carpet is glued to this recession and is secured further with nails. The opposite end of the turf is buried in a 12-inch-deep trench, pegged, and backfilled. The trench-buried turf, in combination with the curbing header, gives the surface a firm footing.

The artificial turf also allows markings to be embedded into the turf. Another collateral benefit of the turf is the view it provides from above. Because artificial turf is evergreen in all seasons, the safe zone contrasts with the adjoining asphalt or concrete runway or taxiway. Such contrast gives a clear landing target and enhances pilot visibility significantly.

Artificial turf seems to outlast asphalt by a factor of three and, if there is minimal maintenance performed on the turf, that number usually increases to a factor of four. In addition to its attributes compared with asphalt and natural grass, there is much to be saved on the maintenance and care of the landscape it replaces.

Joe Dobson is vice president of Air FieldTurf, Milford, Mich. He can be contacted at jdobson@airfieldturf.com.


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