Most sports fields have a flat grade or are slightly crowned. Architects can design the drainage system for surface slope drains, but in most cases, all that is required is a system beneath the grass to capture water to allow it to flow off the field. Geographic location, rainfall, and snow melt determine how surface water is handled. If necessary for an environmentally sensitive installation, for fields and other applications, builders can use gravels with a higher permeability than road base, which allows the surface water to permeate the ground rather than run off. This is helpful in courtyards of multi-family properties where hardscape calculations are necessary, and many commercial properties in which too much surface water is present.
It is also important to consider sports field cushioning and the desired outcome, as sports use requires a surface soft enough to prevent injury, but not too soft as though playing on a pillow. Soccer differs from football, which differs from baseball in terms of field cushion. Field hockey, rugby, cricket, and many other sports require different cushioning approaches based on how the ball is intended to roll or bounce, how the players impact the surface, and how groundskeepers must maintain these surfaces.
The least expensive and most popular form of cushioning is crumb rubber infill on top of the turf; this can be researched for its many problems including heat, sticking to clothing, splashing up during use, and overall displacement, which requires maintenance. Cost, availability, and ease of install make crumb rubber the go-to product. Other systems use padding between the base layer and the turf. While it costs more to install, this padding eliminates any maintenance as it relates to safety. The padding is set in place under the turf and does not move.
Finally, heat is a major concern for synthetic grass installations, as these surfaces can reach up to 66 C (150 F) and, in some cases, even higher. While some limited technology exists to allow the yarn fibers to reflect sunlight, the research has found a maximum of 20-degree temperature drop benefit at most. Infill products (which are distributed on top of the synthetic turf) can absorb moisture and then slowly release the trapped water through evaporation, which has a great effect on surface temperatures. Irrigation systems can be designed and installed specifically for the purpose of wetting the infill to its saturation point.
When considering synthetic grass installation in sports fields, drainage, cushioning, and heat all need to be addressed during the design phase and properly implemented during installation.
Commercial pet lawns
Commercial pet lawn systems need a turf with a high drain rate, but this is just one variable. Traditional synthetic grass has a urethane backing and must be hole-punched to drain. The urethane-backed turf flow rates are approximately 762 mm (30 in.) per hour, and while this may sound fast, some products can provide more than 25.4 m (83.4 ft) per hour, making pet cleanup much easier.
With this much water flowing, one concern is how to get the water below the turf. Drain tiles are placed between the road base or, in the case of apartments and condominiums, concrete sub-surfacing, to create a void between the turf backing and the sub surface to allow water to freely flow. These tiles are 12.7 to 25.4 mm (0.5 to 1 in.) in height and not only allow for the required vertical drainage to get water below the surface, but also for fast horizontal rates, which send the flow completely out of the area.
It is smart to start with a high drainage rate on the backing and then create a void, which allows the water to flow. Through research and development, synthetic grass producers have identified a few problems with pet excrement and synthetic grass. The ability to clean and flush the surface is determined by two factors: the length of the turf fibers and the amount of infill required.
Most synthetic grass for lawns and sports fields have 44.5 to 50.8 mm (1.75 to 2 in.) and taller fibers. These heights allow for the beautiful look of natural grass, but also allow for cushioning infills as well as the use of cleats on the field to help reduce injury. It is important to place 1.4 to 1.8 kg (3 to 4 lb) of infill on these tall fibers to get them to stand up. This normally results in 19 to 25.4 mm (0.75 to 1 in.) or more of infill. This is a good formula when designing sports surfaces on which a ball ought to bounce and roll, mimicking natural grass. Sports fields have head impact standards, which must be satisfied based on a given jurisdiction’s codes and standards. Each installation must be designed for its intended use. The exact product and the choice of cushioning are determined by the use of the area and the desired playing conditions, both strategic specific to each game and for safety to the athlete.
However, pet parks require a different formula to fit their different needs. Proper pet turf for dogs is 25.4 to 31.8 mm (1 to 1.25 in.) tall and 1417 to 1700 g (50 to 60 oz) thick. This shorter pile height and thickness helps with keeping feces on top of the fibers for easy cleaning. It also allows for less infill to be used, normally just 0.5 kg (1 lb). Less infill means less area to hold onto urine or feces and a shorter distance for flushing through the turf. There are certain types of infill which help. Standard round silica sand is the best infill for most synthetic grass installations. If odor or bacteria is a concern, there are other options. Zeolite is a volcanic ash which traps odors and is used in many applications like horse stalls. Antimicrobial additives have been used in coatings of silica sand to eliminate any bacterial growth. Whether it is a dog park or dog lawn at a pet-friendly hotel, it is important to make sure the turf drainage rate is high, use drain tiles to create a void between the backing of the turf and the sub-surface, choose turf which is short, thick, and designed for pets, and specify the installer only uses 0.5 kg (1 lb) of infill.