Cushioning the Fall

Safe playing fields are built upon carefully considered subsurface conditions and an equally solid grasp of the exciting advances in artificial turf products. Using several brands of synthetic grass, one of the country’s largest and most extensive playing field renovations is underway throughout New York City’s five boroughs on sites that conceal generations of urban debris.

Take the Field Inc. is a non-profit group upgrading New York City’s public school fields through a combination of private and public finance. Work is nearing completion, with 37 of 44 fields already refurbished, the large majority under the direction of the architecture and engineering firm of LZA Associates.

Success was achieved by performing “triage” on each project individually, says Dan Marguiles, project manager for LZA, a division of The Thornton-Tomasetti Group. Take the Field visited 52 schools with a representative from the Board of Education, and they rated them on a scale, Marguiles says. They all had unique conditions, and you can’t plead ignorance of what’s below ground.

Poor soil, construction rubble, old landfills, subsurface storage tanks, underground streams, and inadequate storm-water systems were among the impediments to creating stable, long-lasting playing surfaces that drain efficiently. LZA Associates met the challenge in part thanks to extensive experience designing airports, which are notorious for being sited above unsuitable materials.

Anyone can come in and take five feet off every site, and if you do that, every site would cost $6 [million] to $10 million dollars, says Marguiles. That wasn’t an option for Marguiles, who preferred to see each total renovation, including fences and bleachers, come in at under $2.5 million. Typically, we tried to reuse as much of the existing materials as we could, improve the structural performance, and isolate the voids. Preventing differential settlement by improving storm-water performance is the key.

Cost-effective ground improvement options included simply removing old fill and replacing it with lighter weight fill, using rollers weighing several tons to compact the soil, or Deep Dynamic Compaction, repeatedly dropping 12,000 lb. weights from cranes to the ground surface, compacting earth and materials at significant subsurface depths.

Leaping Forward

Aiding the goal of proper drainage, the latest generation of artificial turf systems offers superior drainage qualities. Water runs down into a network of herringbone-patterned, channeled drains under the playing surface and then to the edge of a track. Instead of sheeting off the surface, water enters the storm-water system at a slower, more controlled pace, avoiding puddling and allows playing to resume only an hour after a rain.

Artificial playing surfaces have advanced considerably since the days of AstroTurf, which earned a reputation for causing carpet burn and more serious injuries. Padding systems have since grown more complex and currently receive glowing press, with many professional football players now preferring the new artificial turf to natural grass.

Better footing, more cushion, less abrasion, and reduced maintenance costs are only the most common accolades. Marguiles is also an enthusiast for artificial grass, but he remains a skeptic in negotiation. Although artificial turf manufacturers each like to claim their system is unique, Marguiles says most of them offer comparable products, some of which they might not even actively market.

The challenge, he counters, is getting any given manufacturer to meet your needs and your budget. Some are going to give you their C product, and charge you the A dollars, Marguiles warns.

Sitting down with a turf sales representative can be a dizzying experience, particularly when purchasing a field used for multiple sports with different requirements. Injury criteria, skid resistance, and shock attenuation are some of the factors to be consideredand detailed in generic engineering specifications before bidding openly.

One decision is whether specs should call for padding with 100 percent rubber infill or a combination of rubber and sand. While Marguiles recognizes that an all-rubber infill offers superior performance in many sports, Take the Field Inc. specified the all-rubber infill. Though turf manufacturers would argue that sand-rubber combinations have been enhanced to prevent degradation, Marguiles was concerned that sand can shift, leading to an uneven playing surface.

Cushion

Shock attenuation, or absorbency, hinges on a G-Max scale that rates the hardness of a playing surface, which become harder over time and puts athletes at risk. The ASTM sets a general accepted level of protection for the user at a maximum G-Max rating of 200. Take the Field Inc. specified a G-Max rating of 130 over the life of the warranty, with a rating of 105 at installation, increasing the likelihood the product will perform for at least 10 years without flattening or otherwise degrading.

Too many products on the market give a 200 G-Max, says Marguiles. They give you 150 or 170 initially, and then in five years, Boink!’ We have multiuse fields in almost every case, where a soccer player and a baseball outfielder may be using the same area. You want to ask: What is a good range everyone should be playing on?

Natural-grass die-hards should note that artificial turf is considered a sustainable product because of its good drainage and because it typically contains recycled rubber. And, of course, less maintenance is needed with the new turf systems. But in some cases, LZA determined that staff were doing an excellent job of maintaining their existing grass fields, which, Marguiles says, are most appropriate when dedicated to one sport.

The baseball diamond at New Dorp High School in Staten Island was one such field. Marguiles says the New Dorp crew, working in support of the school’s championship teams under a tight budget, had turned maintenance of the ragged field into an art. It was an even surface even though it was half grass, half weeds, he says. No bald spots, pretty nice.

Turf Makers Compete

Even professional football players, who long complained that the first generation of artificial turf was little more than a green carpet, are warming up to the new high-tech turf, saying it really does feel similar to grass. More NFL stadiums and practice fields are using the product, including a recent installation of FieldTurf at Giants Stadium in New York.

SRI Sports Inc. partnered with Take the Field Inc. to upgrade 12 outdoor athletic high school facilities so far, including South Bronx High School and Adlai Stevenson High School. Some fields also received a Relay track by SRI Sports. The firm’s AstroPlay product comes with an infill of rubber or optional light sand and rubber. Also available is the SRI’s nylon Root Zone for improved shock absorption and infill stability.

Another player in the synthetic turf market is A-Turf, which has completed more than 1,000 synthetic grass fields worldwide using the Regupol underpad and is backed by a coast-to-coast network of installers. A-Turf features three infill and two conventional synthetic grass systems suited for football, soccer, lacrosse, field hockey, baseball, and multi-sport areas.

Meanwhile, the 2012 Turf System is constructed exclusively for SafePlay International Inc. by Polyloom Corporation of America. The company says olefin fibers are softer and less abrasive than monofilament nylon fibers. The fibers do not absorb moisture and are highly stabilized to prevent ultraviolet degradation and fading. Among SafePlay’s four recent projects in New York City are an outdoor soccer/football field for Thomas Jefferson High School and a soccer/football/baseball field at Christopher Columbus High School.