Dr Keith McAuliffe
Managing Director, Labosport Aust.
email@example.com; ph 0406558120
Multi-use of major sporting venues is now the norm.
Multi-use can be particularly challenging where there are limitations with field dimensions. For example, having a synthetic running track around a playing field may enable a sport such as soccer to be played, but will impose limitations for the likes of cricket, AFL and even rugby union.
The turf industry has needed to find cost-effective solutions to enable sports grounds to be extended and in turn allow for safe use by sports requiring a playing surface larger than what was originally available. Technology that enables the extension of the playing surface is readily available. The following outlines key considerations if planning a playing surface extension.
Where extensions to the playing surface may be needed
A common scenario globally is for a sports complex to have a combination of a synthetic running track and a centrally located soccer pitch. This combination can work, even for a full-size soccer field (105x68m), although there is generally only a meter or so runoff from the field to the track in the corners. However, for rugby and rugby league, where an in-goal zone is needed, there is likely to be insufficient turf area, and for safety or playability reasons an extension may be required.
Extensions to a playing surface may be necessary to meet regulations laid down by a sport. For example, a football governing body may rule—especially for tournament play—that there needs to be a sufficient, safe runoff area beyond the touch line.
The options may include constructing a permanent solution by extending the playing field size or providing a temporary overlay that enables the match(es) to be played before removing the overlay. Note that it is possible to adjust the design of a running track to provide extra width in order to reduce—or even eliminate—the need for extensions.
Types of temporary extension systems
Temporary extension of overlay systems can include conventional natural turf, reinforced or hybrid turf and synthetic turf. In the past decade we have seen major progress with “instant play” turf solutions to replace damaged turf, and the technology is also a logical solution for field extensions. Synthetic turf options can appear easier and cheaper to use on face value, but there are additional considerations, in particular the safety elements with a synthetic surface (namely hardness and potential skin burn).
Considerations in the selection of a suitable extension area product may include cost and practicality of the installation; compliance regulations; type of use; duration of use and availability of the product. Appearance—especially for televised events—may also be a factor.
Safety and performance requirements
The extension system used must satisfy the requirements of the user. Safety will no doubt be a high priority—in particular surface hardness, levelness (especially at the junctions) and stability. The user group in question may have regulations that dictate the safety standards expected of the surface. For example, for the 2019 Rugby World Cup in Japan there were clearly defined performance standards for extension areas (as well as the main playing surface) that had to be met before a venue was signed off as fit for purpose. These performance standards covered: dimensions; hardness (including head impact values); traction; surface regularity (levelness); stability and appearance.
Preparing a sports field extension area before laying the turf.
If the extension turf is to be left down for any length of time it is likely to be necessary to incorporate a drainage layer below the replacement turf in order to avoid waterlogged turf if it rains. There are thin (as little as 10mm thick) drainage cell products available.
Drainage layer under the temporary turf to minimise waterlogging in wet conditions.
The success of any natural turf extension will depend to a high degree on the quality of the turf to be supplied. It is essential the turf nursery is planned and booked well in advance to ensure the quality of product is of the best possible standard. Ensure the nursery turf is of a satisfactory thickness for the intended purpose. Thick cut (say 40mm thick) turf would be ideal if readily available, as it would not only offer better playability, but should also be easier to maintain if the extension is required for long duration.
The turf supply should also be consistent in thickness, have minimal mat and be free-draining.
Each site will need to be assessed in advance for specific requirements. For the likes of a running track, it is best to use an impermeable geotextile or plastic product to avoid staining before laying the turf.
Transitioning (junctioning) the extension with the playing surface
Achieving a satisfactorily smooth and level junction between the extension and the playing surface is arguably the biggest challenge with extensions, especially where the field of play turf sits at the same level as the running track or surround to be covered. However, there are options that can achieve a satisfactory result.
The junction from playing field to extension must be smooth and level.
If there is sufficient lead-in time available, one way to build up the in-field level is to undertake a regular topdressing program to progressively (say 10mm at a time) raise up the edge of the playing surface. Another approach is to use a turf cutter (preferably a big roll sod harvester used to maximum depth) to remove the outer 1.5m of turf, add additional sand on the exposed root zone, then replace the removed turf.
Maintenance of the extension area
Regardless of how long the extension is to remain in place, an intensive maintenance is critical for natural turf extension areas. Damage will inevitably be done to the turf during harvesting and transporting. Maintenance guidelines include: water little and often using a soaker hose or similar; apply fertiliser every
week or so in order to retain turf colour; mow and roll the same as the main part of the field; keep a close watch for diseases and disorders such as dry patch.
The extension turf area will require intensive watering and regular fertiliser dressings.
World Rugby is soon to release a web-based publication that provides an in-depth overview of field extensions. Check the World Rugby website for more details.
Labosport has recommended performance standards for extension areas to ensure the surface meets the requirements of user groups.
For site specific information or requirements for field extensions, please contact the author