Selection and installation
Selection, specification and installation of synthetic turf are by no means rocket science, but done hastily, can lead to unsatisfactory or even disastrous results. Ideally an owner will involve a licensed design consultant with significant synthetic turf experience early on to help guide them through the process. A good consultant will never direct an owner to a particular system without clearly understanding their project goals and budgetary constraints, the needs of the intended users, and the owner’s ability to manage and maintain the system. No one vendor or system is perfect for all situations, but with education and careful consideration, an owner can receive a field that is well conceived, specified and constructed to best serve its intended users.
The first step is to determine if “ersatz grass” is actually warranted. Synthetic turf is a tool that can help accommodate additional usage, alleviate wear on other existing fields, extend the playing season and provide playing space in inclement weather. In some situations it may be a matter of keeping up with the Joneses.
The types of sports, levels of play, and nonsport activities, such as graduations and concerts, can all impact the system. Other important considerations include the funds available for installation and the resources required for long-term maintenance and replacement.
Different combinations of fiber height and face weight with varying infills will perform differently, and should be designed to fit the needs of the highest intended use. The configuration of these components can vary greatly for a 15,000-square-foot field for physically challenged youth and a FIFA 2-STAR Certified soccer pitch.
Synthetic turf field bases typically consist of a network of drainage pipes and crushed stone overlaying a prepared subgrade. Their function is to provide a stable and free-draining substrate that quickly removes excess water from the surface.
Creative design may also allow the base to serve needs beyond compliance with local stormwater management criterion. In the spirit of sustainable site development, bases may, for example, capture excess stormwater from other parts of a facility to promote groundwater nourishing infiltration or reuse for irrigation or other nonpotable uses, such as toilet flushing. With proper design consideration, owners may take advantage of the open excavation to install a ground loop geothermal system to heat and cool adjacent field support buildings.
Alternative base systems, such as AirField or Brock PowerBase, may be able to replace the pipes and stone in some situations. Depending on annual rainfall, freeze/thaw cycles, stormwater regulations and other site-specific conditions, these systems may not be adequate by themselves. Be sure to consult with a qualified civil engineer or landscape architect to be certain.
When replacing an existing sand-based field with synthetic turf, it may be possible to remove the sod and reuse the rootzone and drainage system as a base for the new field. This can save money and resources and allow the owner greater flexibility to return to natural grass at a later date. Make sure to properly test the rootzone for stability and infiltration rate and consult with a design professional who has previous experience with these types of renovations.
A conventional sand-based medium may also be considered when building a synthetic field from scratch; especially when the field installation is a one-time grant situation for a municipality that may not have the budget to replace the turf in eight to 10 years. Utilizing these base materials gives the flexibility to remove the turf, incorporate organic matter and seed or sprig the field for continued use.
Turf backings generally consist of two layers. The primary backing is a fabric designed to accept the turf fibers during the tufting process. Secondary backings are glues that secure the fiber to the primary backing. Historically made from latex or polyurethane, secondary backings can be difficult to separate from the primary backing, making recycling technically difficult and financially infeasible. Manufacturers have begun to experiment with heat-applied polyethylene backings, which are made from the same polymers as the fiber and are far easier to recycle.
Fibers are typically made from polyethylene and serve to hold the infill in place and give the field the look of natural grass. Fibers can be slit film or monofilament. Slit film fibers are made from wider extrusions that are slit like an onion bag to give a grass-like appearance. Monofilament fibers are single extrusions that are bundled together to achieve this same appearance.
Recently, synthetic turf vendors have spent a great deal of time marketing monofilament fibers, and the market has responded by moving in that direction. Intended to be thicker and more durable than slit film, monofilaments have not been without their own issues. In certain instances the fiber manufacturers still recommend the tried and true slit films due to their proven record of durability.
Whichever type is chosen, a fiber that remains upright will generally last longer than one that is allowed to lay over. When a fiber lays over, it is more susceptible to degradation from UV rays and damage from the friction and abrasion of shoe interaction. Footwear consideration is also a key to longevity. Although it may be counterintuitive, a 360-pound lineman wearing the proper cleats will do far less damage than a 60-pound child wearing sneakers. To keep the fibers standing upright, select the combination of the shortest fiber length and greatest infill depth to accommodate the specific field use. Periodic maintenance will also extend the life of the field.
A review of scientifically based literature and recent statements from the EPA and CPSC indicate that there is little need for concern with the use of SBR rubber infill; there are, however, alternative products to consider. Thermoplastic elastomers (TPE) exhibit great performance characteristics and can be recycled, but are significantly more expensive. Coated sands have also gained favor due to manufacturer claims of cooler surface temperatures. Recently introduced organic infills made from pre-consumer recycled coconut husk are also gaining in popularity. Though their longevity cannot yet be predicted, FIFA 2-STAR testing protocols completed by Labosport indicate very positive ball and cleat reaction, as well as reduced surface temperatures. These systems do require additional maintenance, and an owner may want to consider the installation of irrigation as they can become dusty and abrasive when dry.
The synthetic turf industry in the U.S. and Canada often takes cues from what’s happening in Europe, including the push for systems that utilize pads in combination with shorter carpet and less infill. Pads range from the conventional e-layers, rubber sheet goods and composites, such as Brock’s PowerBase. In addition to added player protection, a pad can positively impact performance, such as limiting ball bounce and imparting positive energy restitution to the athlete. While initially more expensive, a pad can last several replacement cycles. This means lower replacement costs and less environmental impact.
If budget permits, an irrigation system can be beneficial. Traveling systems are typically less expensive, but do not provide the swifter application and uniformity of an inground system. In addition to cleaning the field and providing limited cooling capabilities, irrigation can also increase performance and aesthetics. Applying water prior to an event can create a firmer and faster playing surface. It also can prevent the buildup of the static electricity that causes the black infill to creep up the fiber blades, which looks unattractive on TV.
Check the options
There are many synthetic turf vendors that are capable of providing commercially acceptable products that can meet many different needs. The key stakeholders should hear presentations directly from the vendors prior to trying to differentiate between the systems and system components that best fit their particular situation.
Warranties vary for each manufacturer. They typically state allowed uses and use hours and require the owner to provide a minimum level of maintenance. In addition to standard warranties, some manufacturers offer “third party” or “insured warranties.” Prior to purchasing a field, have an attorney or insurance specialist closely examine all aspects of the warranty, particularly its limitations. Don’t assume that everything is covered.
Installation quality control
The best way to procure a long-lasting, highly functioning, synthetic turf system is to have high-quality materials properly installed by a qualified and experienced specialty contractor. There are excellent contractors who may have experience building thousands of parking stalls and hundreds of miles of roadways. This does not qualify them to undertake a field project; a demonstrated history of successfully installing bases and coordinating turf subcontracts does.
The removal of an improperly designed or constructed field that does not meet user needs is far more expensive and time consuming than taking the steps to do it right in the first place, and it is preventable if the specifications are the right match for field use and the installation and oversight are done correctly the first time.
Patrick Maguire is principal for the Boston-based sports division of Stantec Consulting. Stantec Sport specializes in landscape architecture and civil engineering services for outdoor athletic facilities and sport venues.