Part 2: Watering Synthetic Turf
By Randy Gaddo
Last month, I looked at the issue of whether or not synthetic-turf fields should require irrigation; basically, the decision has to be on a case-by-case basis, and there are many variables to consider.
Part II of this series is based on the premise that, if the decision is made to put an irrigation system into a new synthetic field, or a natural-turf field retrofitted with synthetic turf, there are various systems to choose from, and I have sought out experts in the field.
In talking with them, I discovered some new perspectives on the original question—to irrigate or not to irrigate—that I think are important.
The conclusion to the previous article was that the question does not have a simple “yes” or “no” answer. It is very much a function of local desires, budgets, competing resources, and the resolve to engage in long-term operations and maintenance of the systems. Anyone looking at synthetic fields should carefully weigh the topic of irrigating them.
The Cooling Effect
One of my sources for the original article was Greg Parker, a landscape architect, who is also a member of the Synthetic Turf Council and very knowledgeable on issues surrounding irrigation. With a background in urban planning and 35 years in the business, he knows the topic from the ground—well, really, below the ground—up.
“When I was in college, one of my professors once said that people don’t start off planning to fail, but they do fail to plan, and that has stuck with me all these years,” he reflects. “You would be shocked at how little most people know about how to move high volumes of water under high pressure for irrigation, and if you get it wrong, you can rarely make it right because of the expense to do so.”
High volume and high pressure are the key words here because they are what’s needed in an irrigation system for synthetic turf. In order to obtain any of the goals expected from irrigating synthetic turf—especially cooling—a large volume of water has to be put evenly on the entire field in a short period of time.
Cooling fields is one of the main arguments for irrigating synthetic fields, which can reach temperatures of 120 to 130 degrees; however, in order to reduce that temperature 10 or 20 degrees, a large amount of water has to be dumped evenly across the whole field—and quickly because players will want to play immediately. And the cooling effect only lasts about an hour, maybe less.
A normal 3-inch supply line looping the field and regular irrigation heads aren’t going to distribute the high volume of water necessary to do this. Also, it isn’t desirable to have regular pop-up heads scattered across the center of the field because the crumb rubber or newer organic in-fill material will interfere with players’ performance. Parker notes there are both manual and automated systems available.
Automated systems consist of pop-up systems of turf guns that can be snapped into a quick-connect and operated electrically from an irrigation system, or turbine-driven or pull-along portable machines.
A manual system can be as simple as the installation of quick-couplers around a field and dragging a hose around to cool or clean the field. Another popular system consists of large water cannons that are operated manually; one at each end of the field can generally do the job. These guns shoot enormous geysers that distribute water down the field, but they have to be physically moved to get total coverage.
“The difference between an automated and manual system is speed,” notes Parker. “An automated system can cool a field in about 15 minutes; it will take much longer to do it manually.”
Parker emphasizes that the best method is to over-engineer the water supply and delivery system, including the pump station, because inevitably the water supply will be tapped for other uses.
“As a new park or sports complex or stadium is built out, people will begin to poke straws (water lines) into the supply line, and all of a sudden you’re not going to have the pressure you need,” he says. “It’s better to over-engineer the system from the start to make it last.” Other sources for this article suggested that the cost to irrigate a synthetic field can double the cost of irrigating a natural-turf field.
This leads back to the central question: Do you really need to irrigate synthetic fields? Parker estimates that the cost will be between $175,000 and $350,000 for proper irrigation, depending on design fees, site conditions, and the unpredictable.
I posed the question: How is a parks and rec professional tasked with a cost-benefit analysis supposed to determine if irrigating a synthetic field is necessary, and if so, what kind of system is best? I suggested it would be great if there was a checklist of some sort to provide the questions that needed to be asked.
Parker said he didn’t know of such a checklist, but agreed it would be helpful; he offered to produce one based on his experience. Generally, a checklist helps determine what you have versus what you need versus what you can afford. That checklist is attached to this article. The checklist was reviewed by the other two experts I talked to for this article. The result is what I hope will be a helpful guide.
Jeff Graydon is the Senior Associate Director of Athletics at Princeton University in New Jersey. He has been an employee at the university since 2006, and before that was a contractor there since 1976. He has been involved in many new and renovated field projects, both natural-turf and synthetic and has definite and passionate opinions on irrigation of synthetic fields.
“The first synthetic-turf field we irrigated was a football field in 2006,” he recalls, noting that it was a natural-turf field converted to synthetic and that the “big guns,” water cannons, were used because the university didn’t want small heads all over the field. “We thought we needed irrigation for heat control and to clean the field; however, we turned it on maybe twice in 10 years. We discovered that with hose bibs and a good hose we could go out and do what we needed to do—and we didn’t have to winterize them like we did the big gun system every winter.”
Graydon says that the field was replaced this year with new synthetic turf, and it was not irrigated. “Our football season starts August 20, so we may only get a few hot days where the fields would get hot enough to think about watering them, and if needed, then we could do it manually with hoses.”
Graydon also points out that using any kind of irrigation system to cool a field may cool it down for maybe an hour, but “Then you have hot, wet turf, and when it dries out, you have hot turf again. Fortunately, in our college environment, students don’t have to practice at two in the afternoon; they can practice earlier in the morning or later in the evening.”
Drawing a parallel to another safety measure regularly exercised by teams, Graydon notes, “We don’t play in thunderstorms either.”
The exception that Graydon notes is irrigation for field hockey, which uses short, nylon-turf material. “Irrigation has become the norm for field hockey because field consistency is so important in that sport for ball control,” he says. “Uniform ball bounce and a non-directional roll are important, and you want the ball to stick to the field, so when fields are wet, they perform much better for field hockey.”
He explains that when Princeton needed to retrofit a natural-turf field with synthetic turf, the best irrigation method was two moveable water cannons, starting in the center and moving to each end. Princeton used about 12,000 gallons of water each time the school watered in the peak season in September and October. “If we’d only used one, it would have been dry at one end by the time we reached the other end,” he says.
As for the cleaning benefits of irrigating fields, he notes that in New Jersey, “We get ample rainfall that washes the fields clean,” explaining that hand watering and rainfall, plus the cleansing action of sunlight, safely cleans away sweat, blood, or other foreign debris.
If an irrigation system needs more than hose bibs and standard hoses, Parker says that his company introduced a manual system two years ago, using a large quick-coupler that connects to a high-volume hose similar to hoses used by firefighters and in jet fueling. He says that with a system of three coupler boxes on each side of the field and two water guns, two men can cool a field in 15 minutes, more or less, depending on how fast they run from box to box.
Another key point that Parker makes is that properly grooming synthetic fields to maintain consistent performance and safety is important, no matter what type of watering system is used. “Not everybody knows how to groom fields,” he says. Keeping the turf leaves brushed and the in-fill evenly distributed is critical.
“It takes three or four hours to properly groom a field,” Parker says, adding that it takes someone who is competent and has the time to do it. “If you’re not going to properly groom the field, you may as well not build it.”
Worth The Investment?
Michael Krones, with a Ph.D. in Agricultural Engineering, is also President and Principal Designer with Hydro Designs, Inc. He specializes in non-potable, water-related projects, including development and maintenance of synthetic- and natural-turf irrigation systems.
Krones agrees that in many cases irrigating synthetic fields is not entirely necessary, and, in fact, many parks departments can’t justify doing it from a cost-benefit standpoint. He also makes the point that irrigating hot fields can cause more problems for players because as the water evaporates, it creates humidity and, as we all have heard, it’s not the heat, it’s the humidity.
However, he goes a step further and makes the somewhat alarming statement that “I will be surprised if synthetic fields continue as they are.”
Newer in-fill materials have lessened the issue of heat gain on fields. In-fill is the material that is worked down into the synthetic turf to keep it standing rigid, and also to act as a shock absorber when players hit the ground.
Crumb rubber in-fill—generally tires but more recently tennis-shoe soles—has been the status quo for years, but has been the subject of inconclusive claims that they carry health risks due to a petroleum base. Rubber can also store and transmit heat.
Newer “organic” materials include rice husk, cork, coconut shells, and a combination of the two called cococork or corkonut. These materials don’t get as hot as rubber and tend to shed the heat more quickly. So irrigating to cool the surface (which isn’t all that effective anyway, according to our experts) isn’t necessary. “With organic in-fill, irrigation is only needed to keep dust down,” says Krones.
He mentions a project in which a park district decided on a synthetic field during conceptual phases six years ago; then they became concerned about the heat gain and were looking at irrigation, and heard about organic in-fill to reduce heat gain.
However, the in-fill vendor cautioned the district about the need for moisture content. “They gave me a change order to put irrigation on it,” Krones explains. “The budget blew them away; it more than doubled the cost of the irrigation system for this park. Each sprinkler needs about 300 gallons per minute and lots of pressure to get the water out quickly. We went from 4-inch mains to 6-inch mains; from 130 gallons per minute to 300; from 70 psi [pounds per square inch] to 115; and made a huge increase in cost.”
Roughly estimating, he notes that irrigating one synthetic field is like irrigating three natural-turf fields, due to the need for high pressure and high volume to achieve fast and even distribution of water.
Another environmental issue that may drive a decision to irrigate artificial turf is water usage. As Graydon points out, water is going to become (or has become) a number-one commodity in the U.S. and around the world. It becomes a matter of sustainability. Is unnecessarily irrigating a synthetic field environmentally irresponsible?
A rhetorical question perhaps for the scope of this article, but still an important one that should be considered.
Randy Gaddo served for 15 years as a director in municipal parks and recreation after retiring from 20 years in the U.S. Marine Corps. He earned his Master’s degree in Public Administration and is now a full-time photojournalist living in Bay Minette, Ala. Reach him at (678) 350-8642 or firstname.lastname@example.org.