LaGuardia Addresses Unique Rubber Removal Needs

Roughly five times per year, crews work from midnight to 5 a.m. removing rubber deposits from the two main runways at LaGuardia Airport (LGA) in New York. They work through the night until the break of dawn because that's the only time the airport slows down enough to allow access. They also come more often than at other airports.

"Because of the shorter runways at LaGuardia, rubber builds up quicker than it would on longer runways," explains Ron Marisco, a spokesman for The Port Authority of New York and New Jersey, which operates the airport. "Thus, our operations staff there has instituted a process by which derubberization is conducted five times annually - far more than typical at airports with longer runways. While not required, such frequent work is done out of an abundance of caution by safety-conscience staff."

Shorter runways - 7,000 feet at LaGuardia vs. up to 12,090 at Los Angeles International, for instance - require more sustained braking during landings, which leaves more rubber on the runway surfaces. The volume of aircraft at LaGuardia - 379,000 total flights last year - further compounds the effect.

Regular removal of rubber deposits is vital to preserve proper braking performance and directional control for aircraft using the runways.

The type of aircraft landing also affects rubber removal needs. When widebody aircraft account for more than 20% of the total aircraft mix on a particular runway end, the Federal Aviation Administration (FAA) recommends upping removal frequency one level. (See chart 24.)

Double Duty

The FAA lists four recommended rubber removal techniques in its Advisory Circular on the subject (AC 150/5320-12C): high-pressure water, chemical solvents, high-velocity impact (using abrasives) and mechanical grinding. LaGuardia's contractor, Hi-Lite Markings, uses pressure washing and chemical solvents.

The company's pressure-washing unit, a tractor-trailer called the Hydro-Blaster, sprays water pressurized at 17,000 to 20,000 pounds per square inch - powerful enough to dislodge rubber deposits but not harsh enough to damage the runway surface, paint or joints, explains Brian Becker, director of sales and marketing for Hi-Lite. The vehicle is built in-house and includes a 48-foot drop-deck trailer that holds a water tank with an air-gap backflow prevention device and filtering system that filters water down to one micron, says Becker. The trailer can cruise at highway speeds when in transit, but moves just 30 feet per minute when it's cleaning. Employees must attend more than a year of training before operating it on runways.

The chemical solvent Hi-Lite uses is called Hurrisafe 8035. "Each ingredient used in the formula was chosen after exhaustive testing to ensure that Hurrisafe as a completed formula was readily biodegradable, contained no hazardous air pollutants and contained no ingredients that would cause problems upon disposal," specifies Bobbie Pettit, director of technical services for Hurrisafe. "Knowing that our product is used on the runway where runoff will go directly into the surrounding soils, it was important that Hurrisafe was readily biodegradable so we did not have any danger of contamination to any water source such as nearby wells, rivers and lakes."

Dissolving rubber residue from aircraft tires presents particular challenges because it changes its composition when it is deposited on the runway. What's left behind, explains Pettit, is synthetic rubber and natural rubber, which is thermoplastic and becomes soft and sticky with heat. Both, she notes, are easily dissolved with Hurrisafe's formula.

About 550 gallons of the product are used for a single 150,000-square-foot touchdown area at LaGuardia. Four areas, two on each runway, are typically cleaned - one per night - during the airport's five to seven annual rubber removal events, bringing its estimated chemical use to roughly 8,000 gallons per year.

Blast Away

Hi-Lite's two-part process begins with the Hydro-Blaster spraying water to cool and wet the touchdown area of the runway that will be cleaned. Then, an applicator and vacuum truck sprays Hurrisafe 8035 starting at the center and working out toward the edge lines. The chemical is left on the runway just long enough for the applicator and vacuum truck to make its next pass.

Next, the Hydro-Blaster begins at the centerline of the area and washes a 6-foot-wide path at an average pace of 30,000 square feet per hour. Once the Hydro-Blaster has cleaned a few passes, the applicator and vacuum truck stops applying the chemical solvent and returns to start vacuuming. This prevents debris and runoff from reaching nearby soil or turf areas, notes Becker.

The truck continues alternating between applying the chemical ahead of the Hydro-Blaster and vacuuming up potential runoff after it. The applicator and vacuum truck contains a drain system that allows runoff water to be emptied into approved wastewater treatment systems while catching solid waste inside a hopper for disposal elsewhere.

The combination of the pressure washing and chemical solvents creates a "fast, environmentally safe and effective method," summarizes Becker. Using its two-method process during five-hour work windows available at LaGuardia, Hi-Lite can clean one touchdown zone - roughly 50 feet wide and 3,000 feet long - per night.

The Airport's Approach

The FAA cautions airport operators about the variety of rubber removal methods available: "The ultimate success of any method will depend on the expertise of the equipment operator. Results can vary from completely ineffective to a situation where all rubber deposits are removed, but the underlying pavement is significantly damaged."

It urges airports to require contractors to demonstrate their effectiveness by cleaning test sections. It further warns that visual inspection is not a valid evaluation method of their work and recommends tests conducted with continuous friction measuring equipment.

LaGuardia management acknowledges the advantages of Hi-Lite's dual approach - especially for its particular runway surfaces.

"Runways at LGA have grooves to channel water and ensure increased traction for a plane's tires," notes Marisco. "Eventually, the rubber deposits left behind from numerous landings and also takeoffs can fill the grooves and cause a slick surface. We've found that applying pressured water and chemicals at proper levels to the runway works well to unclog the grooves and maximize the traction on the runway surface."