This posting is excerpted from the Bay Friendly Landscape Designer blog (http://www.bayfriendlyblog.org/2014/07/synthetic-turf-friend-or-foe.html#more) written by Corrie Lindsay, Sr. Landscape Architect at Firma Design Group.
My name is Corrie Lindsay. I am a Licensed Landscape Architect and Bay-Friendly Qualified Designer, with professional certifications in irrigation design as well as stormwater pollution prevention. I’ve been designing with Bay-Friendly principles before I knew of the Coalition, because I believe it enables the true beauty of the Bay Area to shine. I do what is right for our environment and I try to share my stewardship with others. But when it gets to the topic of synthetic turf I find it difficult to know which stance to take, particularly considering the recent drought.
The average turf lawn (1,000 sqft) annually consumes approximately 50k – 60k gallons of water. Based upon a 0.3115 gallon. per square foot, for a half inch of precipitation, watered 182 days (every other day). Turf’s thirsty character is why Bay-Friendly offers public “Lose Your Lawn” talks. However, there are recreational situations that require mowed lawn. When we talk about an entire soccer field, we are looking at 75,000 sqft of mowed lawn, which is a staggering 4,263,656 gallons of water per year or 77 typical front lawns. That refers to a typical Kentucky blue rye grass with poor distribution irrigation type numbers, but it’s more prevalent than the average consumer realizes. With the Bay Area ground water table dropping more than a foot every year, snowpackat an all-time low, climate change at work, federal farming water allocations being cut by the government, and our local water boards limiting use & raising rates, Water is no longer a limitless resource. But is synthetic turf the answer?
There are two solutions to the typical water consuming soccer field. Personally, I would design it as a natural turf field, but I would use a lower water use grass species. Rye grass is a cool season turf at an AVG. of 80% evapotranspiration (ETO). A simple warm season grass such as a Bermuda grass is only 60% ETO—a 20% savings in water consumption simply by selecting a different species. There are many native grasses on the market, but not many of them can handle the wear and tear of recreational sports. A possibility would be a fescue blend, which can get you down to 50% ETO or 55% ETO, but it comes with a risk of not preforming well with increased use. So the choice of turf species is really going to depend on demand. The more the turf gets used, the more wear and tear means more resources to repair it. Fertilizer applications to promote growth bumps up a turf’s water consumption. A traditional irrigation system has an average of 50% Distribution Uniformity (DU), but a newly designed low precipitation overhead system can reach an average DU of 70%. This is an additional 20% of water savings. With a professionally designed system and a climate correct grass species a typical soccer field can have a 40% reduction in water use. That is still 1,705,462 gallons of water consumed per year or about 31 typical front lawns.
Synthetic turf could save 1.7 million gallons of water per year? WRONG. That is a common misconception. You have to irrigate synthetic turf. People often overlook this. In the athletic field design world, we call them cooling systems. At extreme conditions a synth turf field can reach upwards of200 degrees Fahrenheit, which will melt the rubber cleats right off your feet. This means a cooling system is required in hot climates. Typically six high pressure water cannons are run for 10 minutes before a sporting event. Each cannon puts out 100 gallons a minute, so in 10 minutes a field receives six thousand gallons of water. Note: this is for extreme situations only and can easily be avoided, especially if the level of play is not highly competitive. It’s more of an issue in the Central Valley as opposed to the Bay Area, but the cooling systems can also serve as cleaning systems. Blood, snot, urine and stomach acids all find their way onto any field and synth fields have to be washed down. The most common practice for a cooling / cleaning system is a hose bib for spot treatments, which from a water use stand point is an acceptable practice. An average hose uses 8-12 gallons per minute, so if someone cleans an area for fifteen minutes they use about 150 gallons. Incidents may be more or less, so for this purpose we will say 150 gallons per day for 365 days, which is 54,750 gallons per year. Compared to the most efficient field it’s a savings of 1.65 million gallons per year, enough to water 30 typical lawns
That statistic led me to second guess myself. Maybe we should be using synthetic turf? If you are as concerned as I am, let me help you take a deeper look into the evolution of the synthetic turf market. Typical concerns included, lead in the rubber fines, chemically produced landfill bound material and silica leaching into the soil. These were all valid concerns in the 80’s when Astro turf was the leading manufacturer. Thanks to the EPA and other regulation boards products now on the market contain 0.00% lead. The fibers are made of polypropylene and/or polyethylene and come in a slit film or monofilament version. These are the same chemical compounds as PVC pipe that you put in the ground for your irrigation systems. Then there’s the infill material; which used to be cryogenic rubber or recycled rubber and silica carbide (sand). This material is still on the market today and can tend to have some small trace amounts of pollutants, but all products meet EPA standards and local testing minimums. There are alternatives, such as cork which has shown to reduce heat island effect by 30%. Rather than chemically produced silica carbide there is a naturally mined replacement called Zeofill which is the geologic mineral zeolite mainly from quarries in Nevada. The manufacturers have come up with a plastic material equal to drip irrigation held down with cork and rock. It has reduced the carbon footprint of a synthetic field production by 66% because the infill is now natural without any chemical production. According to the manufacturer, this type of application would be appropriate up to a high school level.
The other half of this argument is the base preparation. Modern synthetic field base prep is more complicated than building a road and can impact the top 24 inches of soil not including drainage systems. Various synthetic geotextiles and pads are placed in a sandwich with different sized rock fines. For contact sports like football the field has to meet certain impact regulations. The test measures shock-attenuation and is called a G-max test. A synthetic foam or pad is used to obtain lower levels of G-max. This Synth material can be another product that is landfill bound and increases the carbon footprint. An alternative to the shock pad or drainage pad is a 100% recycled material called GreenFoam. Used in playground areas, this pad is recycled from non-contaminated postindustrial cross link closed cell polyethylene foam. The pad can also be recycled post field life, but it comes with an 8yr warranty. The Pad is necessary for playground areas, and rugby & football which have higher G-max requirements. For lower impact sports like soccer, baseball, field hockey, lacrosse or ultimate frisbee the base pad is not required. A field with the correct installation and maintenance of a sand base can easily meet G-max requirements. Native local sand and crushed gravel mixes can create an excellent synth base with a very small carbon footprint impact.
Drainage systems are crucial to the success of any competitive field. Without drainage a field will destroy itself whether it is synthetic or natural turf. The systems for the two separate types of fields are the same. Sand channel slit drains, flat drains, capillary action systems or water re-use for irrigation. The systems can be as complex as you want them, but cannot be compared to each other because they can be used in a natural or synthetic field. The one difference is that natural turf fields have a growing medium with organic matter and are capable of building a healthy living system as opposed to a barren one. During the construction of a synthetic field topsoil is removed, herbicide is sprayed and in the winter expansive soils are lime treated. Lime treatment is the death to all soils. Once a soil has been lime treated there is no rehabilitation. The soil can be re-used as structural fill, but it would require too much to amend it. Lime treated soil loses all its cohesive properties and has a PH around ten. Soil sulfurs can be added to amend the PH back to seven, but without cohesiveness the soil remains inhospitable to organisms and fungi. It’s imperative to avoid lime treating during synthetic field installation. If a project site has extremely expansive soils, please consider a natural turf field. It will be difficult to achieve a competitive (level) field in an expansive soil situation. One of the ways to avoid this is proper construction scheduling. Excavation, drainage and base prep all have to occur without rain. If proper drainage systems and a compacted base are in place before a rain event, the field will not be compromised. Another topic to mention is non-toxic herbicide alternatives. Heavy applications of round-up can be more detrimental to a soil than lime treatment.
In conclusion synthetic turf fields are a solution to water conservation. Applications specifically relate to recreation. From backyard play areas to high school fields, synthetic turf is a solution to consider when the correct products and procedures are in place. Natural turf recreational fields can be designed to minimize water consumption and will reduce heat island effect. The tradeoff is up to the consumer. Project location, conditions and amenities will determine if a project will be synthetic or natural turf. Now I am comfortable designing either type of field because I know both of them have their benefits. Most important to the Bay-Friendly Coalition is to correctly identify your recreational needs. Use the local school or parks facilities for your recreational needs and lose your lawn! If you choose to create your own recreational space please consult a professional and always ask for the latest eco-friendly products.