One of football’s biggest stars is often ignored: the field the game is played on.
There’s a lot more to a great field than grass or dirt. Just ask Donny Jones, regional vice president of FieldTurf.
Jones has overseen the installation of several synthetic turf fields for NFL stadiums. Players overwhelmingly prefer playing on artificial turf compared to natural grass. Twenty-one NFL teams now use FieldTurf synthetic grass, and nearly half of all NFL stadiums use synthetic turf.
Jones sat down with Washington Rock and explained how each layer of a synthetic turf field is important to the whole. He also explained why Washington Rock’s sports field aggregates have been the product of choice for high-profile field installations like CenturyLink Field.
Underneath the Surface: The Layers of a Synthetic Turf Field
In the world of professional sports, a well-built sports field means safer game play. The NFL and other sports agencies provide specific guidelines for how a field must be constructed.
The NFL’s guidelines are so important that fields are examined and certified 72 hours before each game. Fields that don’t meet the standards have to be fixed and retested.
As shown in the diagram above, the main layers of the field are the compacted native soil, the stone foundation, the e-layer pad, and the infill that sits between the synthetic grass blades.
The Field’s Foundation: Permeable Aggregates
To drain well and last a long time, a synthetic turf field needs a great foundation. That’s where permeable aggregates come in.
“Permeable” means that water is able to pass through the foundation, and “aggregates” are the technical term for stone products. FieldTurf uses a specific gradation, or formula, of permeable aggregates to accomplish two tasks: helping the field drain and creating a level, stable playing surface.
Drainage pipes are integrated into the stone foundation to help divert water away from the field.
Donny Jones explains that it quickly becomes obvious if the wrong aggregates are used because “the turf will mirror that top level of stone.”
Jones has come to trust Washington Rock Quarries to produce permeable aggregates that are consistent and high quality.
“Washington Rock’s quality control and their key to detail really helps us produce the best base that’s permeable, smooth, and level,” Jones says.
The Field’s Airbag: E-layer
E-layer pads are like the airbags of a field. Located just below the synthetic turf and above the foundation, the pad is a layer of rubber that cushions a player’s fall.
Because rubber is so light, FieldTurf adds Washington Rock’s e-layer stone to their e-layer mixture. This adds ballast to create a pad that is “soft yet firm,” Jones explains.
The process of installing the e-layer pad resembles the spreading of asphalt. A forklift holds a bag of e-layer mixture above the field’s foundation and deposits it onto the field in a long line. Then another machine compresses the material and levels it out. Crew members use special tools to smooth out any imperfections.
Washington Rock’s e-layer stone is made to meet a strict sieve size and has to be 100% dry. Otherwise, the moisture in the rock could ruin the e-layer mixture and force the crew to tear up the pad.
FieldTurf has used Washington Rock’s e-layer stone on many projects throughout the Pacific Northwest, including the following:
- Brighton Playfield in Seattle, WA
- Garfield High School in Seattle, WA
- Glacier Peak High School in Snohomish, WA
- Husky Stadium in Seattle, WA
- Lynnwood High School in Bothell, WA
- Phil Johnson Ballfields in Everett, WA
- Sam Barlow High School in Gresham, OR
- Sehome High School in Bellingham, WA
The Field’s Topsoil: Infill
Rolls of synthetic turf are placed on the field and unrolled. Then the edge of each piece of turf is sewn to the edge of its neighbor, creating a giant patchwork quilt of sorts. Once this turf quilt is perfectly smooth, it’s secured in place using stakes.
At this point, the synthetic turf lacks just one finishing touch: infill. Synthetic turf is just like a carpet but with glossy grass blades instead of soft carpet fibers. Those grass blades would not remain standing long without the help of infill.
Infill is like topsoil for the field. Usually, it’s a combination of sand and a springy component, like crumb rubber, coconut husk, or cork.
The infill sand provides ballast, weighing down the carpet so that it doesn’t ripple. The sand also acts like a cushion and tempers the springy material so it’s not too bouncy.
“One of the reasons that we use Washington Rock with our sand is because it meets the high quality standards that we demand,” Jones says.
The infill is spread in layers on the turf field, then brushed to the bottom of the carpet with a special machine. A typical field contains 150–375 tons of infill sand mixed with a springy material. The depth and evenness of the infill is tested as part of the field certification.
FieldTurf has used Washington Rock’s infill sand on many projects throughout the northwestern United States, including the following:
- Autzen Stadium in Eugene, OR
- CenturyLink Field in Seattle, WA
- Eugene Civic Park in Eugene, OR
- Husky Stadium in Seattle, WA
- OSU Softball Complex in Corvallis, OR
- Portland Timbers’ Providence Park in Portland, OR
- Puyallup Valley Sports Complex in Puyallup, WA
- The Dome in Anchorage, AK