Extreme weather conditions render artificial surfaces unplayable, as they do natural turf playing surfaces. That's all I have to say about that before we get entwined in that never ending debate about artificial verses natural turf.
Snow and ice doesn't pose a threat to your artificial surface if left alone and permitted to melt naturally but, as Bill Pomfret from UK artificial carpet manufacturers and installers, Thornton Sports, explains; "Snow and ice can result in a pitch being unsuitable for use due to the risk of damaging the surface and the health and safety implications." This view is echoed by Matt Magee, who is the Marketing Director for artificial carpet manufacturer, TigerTurf (UK) Ltd; "The turf structure will freeze in conditions lower than minus five degrees centigrade. It is not advised to use the surface in these conditions."
Further clarification is given by Sean Colbert, who is the Area Manager for artificial surface manufacturers, Playrite. "Just like any outdoor facility, a synthetic surface of any specification will be susceptible to extreme weather conditions, such as harsh frost. Low winter temperatures will allow for the freezing of any moisture present in the infill of the carpet. A vast majority of outdoor carpets will contain a sand component, and such aggregate at the base of the carpet is likely to retain moisture for some time, especially during the winter months. Low temperatures will allow this moisture and, consequently, the sand to freeze. This can severely inhibit the playing and draining characteristics of the carpet and pose a Health and Safety risk to the users of the facility."
Regardless of the weather conditions, many sports facilities will want to see a financial return on their investment in an artificial sports surface, which means maximising play all year round. If it's covered in snow it needs to be removed, or does it?
"In terms of snowfall, we recommend that if there's just a relatively light dusting, the best way to try to clear the surface is actually to play on it," suggests Bill Pomfret. But what constitutes a light dusting of snow? 0.5 cm according to TigerTurf's Matt Magee; with the caveat that the surface can be played on as long as the line markings are clearly visible. He does, however, recommend that users take extra care during periods of adverse weather.
If you do have snowfall greater than a light dusting, what's the best way to remove it? The Sports and Play Construction Association (SAPCA) Code of Practice for the Maintenance of Synthetic Sports Surfaces suggests the use of brushes or wooden scrapers, advising against the use of metal shovels or scrapers as they may damage the surface. Realistically, any sharp edged scraper, irrespective of the material it is made from, will pose a potential risk to damaging seams or the carpet itself.
Hand tools are fine for clearing snow on small areas, such as a single tennis court, but larger areas, such as a full size pitch, will require a lot of manpower or something more mechanical. The SAPCA guidelines advise against mechanical snow removal equipment, but doesn't state why!
Bill Pomfret has a more realistic and practical approach; "A pitch can be cleared with a snow plough that has been fitted with a rubber edged snow guard. Note, however, that it is important to clear the snow to a height of approximately 5cm only, as the frozen turf could be easily damaged if the snow is ploughed too deeply. Brushes can be used to clear the remaining 5cm of snow from the surface. However, be aware that the infill may still be frozen."
As an experienced practitioner of groundsmanship, Mark Freeman, who is the Head Groundsman at Loughborough University, has a wealth of knowledge and expertise. As he is responsible for the sports surfaces at a sporting university with elite level athletes, he has to keep the surfaces in play as often as possible, mindful of player safety. Mark points out; "Removal of infill during snow clearing has often been cited as a potential problem, but this is minimal compared to the amount of infill on the surface and has little effect on the carpet. In fact, if the snow is pushed to the fence, most of it can be redistributed by brush once the snow has melted."
Sean Colbert adds; "Extreme care needs to be taken in the case of this [heavy snowfall] and, if the practice is to be attempted, it should be done in degrees, and in the direction of the seams to help avoid damage. Issues in the past with this method have been running out of space at the edge of the surface to store the removed snow, and removal of infill that needs to be replaced - at an expense - when temperatures have returned to normal. It should also be remembered that the removal of the snow may only reveal a frozen pitch beneath that may itself be unplayable."
Can you play on a frozen surface?
So, what if that scenario comes true, you clear the snow only to find that, indeed, the pitch is frozen - can you still play on it? Again, it's a question of to what degree the pitch is frozen, is it just frozen, or rock hard solid frozen?
"Typically, the surface will be required for use before the surface has had a chance to melt. If a good foothold can be achieved in the infill (by using studded shoes), and it is safe to do so, then the pitch may be used," says Bill Pomfret. "However, heavy use of a frozen pitch should be discouraged, as the fibres become brittle at low temperatures and, therefore, may be damaged. Furthermore, the shock absorption of the fibres is reduced, increasing the possibility of injury being caused to the players."
The SAPCA guidelines concur on this issue, adding that players should be made aware of the fact that the degree of shock absorbency the surface can offer will be substantially reduced, and that Health and Safety should be a primary consideration.
Bill continues; "in cases where heavy rain falls on a frozen pitch, or snow and ice thaw quickly, the field may become flooded, as the frozen sand infill prevents the water draining. A pitch flooded in this way should not raise concern as the pitch will drain when the infill has thawed."
How can you prevent frost occurring in the first place?
It is possible to pretty much guarantee a 100% frost free surface if you cover the surface with an appropriate cover before the frost appears. In truth, this is a lot easier said than done - even small areas, such as tennis courts, will require a fair amount of effort to cover and uncover. Then you have the problems of storing the covers whilst the surface is in play. The larger well-heeled sports facilities may have an inflatable dome that can be erected on the surface, but it is likely to interfere with play as a high lobbed ball will probably hit the ceiling of the dome and stop dead in its tracks.
So, what can you use to prevent frost occurring? It's perhaps easier to say what you can't use. Everyone contacted for information for this article from carpet manufacturers to maintenance contractors, end users, SAPCA and in-house staff said a big emphatic 'NO' to the use of rock salt and chemical de-icers on artificial turf surfaces.
"Rock salt and chemical de-icers should NOT be used, as they can damage the UV stability of the surface," said Bill.
Sean Colbert is in agreement; "The use of rock salt or similar products must be highly discouraged, the various contaminants within this salt break down and sit at the bottom of the carpet, possibly affecting drainage and causing standing water. Not only that, the various nutrients within the salt will provide a resource for various mosses and algae to form within the surface. This is likely to lead to problems with the pitch for years to come."
What is the best method then? Tim Jenkins from Amenity Land Solutions (ALS) narrows it down to two types of product; "For customers with synthetic surfaces, clearing them of frost at this time of year can save fixtures and secure revenue. Two products can be considered ice melt (urea based) and pure dried vacuum salt. Again, it is a case of identifying the types of artificial surface you have, as urea based products may be okay on asphalt, acrylic, rubber and so on, but are best avoided where artificial turf carpets are concerned."
"Only pure dried vacuum salt (PDV) should be used on carpets, and surfaces should not be played on during extremely cold temperatures, as there may be a possibility of damaging the fibre or carpet backing," says Sam Breeden, Managing Director of artificial maintenance company, Sweepfast Ltd. "Urea based de-icers have the potential to damage the latex backing [of the carpet]," he suggests.
So, what is pure dried vacuum salt?
"An option in the past has been to use a salt on the freezing playing area," explains Sean. "What's very important to remember is that the salt used needs to be a certain variety, in the same way that only certain infills in the carpet are fit for purpose. Salt needs to be near a human consumption standard - sometimes known as vacuum dried salt - as this product will be extremely low in any contaminants, and will act more readily and quickly on any frost build up."
Mark Freeman uses PDV salt and summed up his regime thus; "We've been putting pure dried vacuum salt on all of our artificials for the best part of twenty years, with the blessing of the installers. There are times to use it and times not to, but that comes with experience, we have even used water to wash away frost and remnants of snow on the water-based pitch, but timing is critical."
"We have also used snow ploughs, snow blowers, push squeegees, tractor mounted brushes, and students with plastic shovels and buckets to remove snow, but a lot depends on the depth and type of snow; I sound like British Rail. We have tried urea once before but found it fairly ineffective."
"PDV salt works well, but doesn't last very long, as it is soon flushed away with the melting ice, so keeping surfaces frost free comes at a price."
Ultimately, it is down to the budget available to prevent or remedy a frozen surface, that dictates whether or not a venue will remain in play.
"Some drawbacks of this will inevitably be the cost of the process, as well as the fact that the product will only work for so long and only down to a certain temperature," says Sean. "These conditions may be acceptable to the operator of the surface if they have a specific important event at the facility."
Environmental effects of using De-icing agents
Are de-icing products harmful to the environment? The environmental impact of using salt to de-ice roads has been reviewed by the Environment Agency, and gives an indication to the effects that using salt on an artificial sports surface would likely have on the environment.
"Salt, or sodium chloride, is the most commonly used material for de-icing roads in winter," say the EA. "Whilst there are minimal short-term impacts to the ecology of watercourses, the salt intake is not prolonged enough to cause significant long-term damage. As salt from roads tends to enter watercourses during a thaw, the salt is diluted relatively quickly."
"Road run-off contains low levels of many potential pollutants which, in some cases, require treatment through interceptors or settlement ponds in the drainage system before it enters watercourses. We [The Environment Agency] have worked with the Highways Agency on this for many years to reduce the impact of road run-off in the UK."
"We do sample streams in the spring, and have found no evidence of significant impact on wildlife from river salt intake. A study was undertaken on the effects of road run-off, including salt input, between 1998-2003. It concluded, for motorways and trunk roads at least, that the use of road salt for de-icing doesn't seem to have any significant impact on river ecology."
The use of urea as a de-icing agent, however, requires greater attention, especially if the outfall of a sports pitch drainage system flows directly into a water course, as is the case with many artificial pitches.
The Environment Agency's Pollution Prevention Technical Information Note, produced in December 2010, states that the environmental impact of urea is that it breaks down to ammonia and nitrates in the water environment, with the ammonia being toxic to aquatic life, even at low levels.
The Technical Information Note comments that there is a 'presumption against the use of urea unless [the] area to be de-iced drains fully to a treatment plant or is fully contained'. From this statement it could be inferred that PDV salt is the safer option, from an environmental stand point.
How much PDV salt do you apply?
A full sized pitch will require a lot of PDV salt, as much as one tonne according to Sweepfast's Sam Breeden. TigerTurf's Matt Magee suggests a rate of 0.15 kg m2 when using PDV salt.
Marie Cooksey recommends that you obtain guidelines from the contractor who installed the pitch, and the manufacturer of the carpet. This is a prudent approach, as it should ensure that you don't carry out any procedures that could affect the warranties on the pitch.
Summing up frost management on artificial surfaces Bill Pomfret says; "Overall, the best course of action if a pitch is covered in snow or ice, is simply to allow the surface the thaw. However, if user demands deem this not possible, be careful to follow these guidelines to protect your pitch and the players upon it."
This article is not the definitive answer to the best way to prevent or solve frozen artificial turf surfaces, as it isn't backed up by hard scientific research. A materials scientist would be better placed to explain the effects of different chemicals on the stability and longevity of the various materials that form the artificial turf carpets available today. That said, the carpet manufacturers who contributed to this article gave recommendations which are more than likely based on scientific research by the aforementioned materials scientist.
Finally, I would like to give the last word to one Head Groundsman, who will remain anonymous, who in a blunt but matter-of-factly manner stated; "To be honest, it is a load of old cobblers, if the snow comes thick, you're knackered; you've just got to wait until it is manageable. If you allow play on it when it is too deep, it packs down and takes three times as long to thaw. If you salt too soon you can end up with a glaze, which freezes rock hard and then takes even longer to thaw. Your best bet is to accept these are not 'all weather' surfaces and shut the facility down until the snow has thawed naturally."