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3.3 Natural Grass
3.3.1 DESCRIPTION
Since the arrival of “all-weather” synthetic running track surfaces in thenineteen sixties, their use has increased substantially and they are now accepted
as the best available surfaces for athletics competition. However the use of natural
grass is still permissible and often forms the only achievable surface for the many
locations unable to secure the substantial finance necessary for a synthetic track or
a track with an unbound mineral surface. Also grass surfaces are ideal for intensive
repetitive training by middle and long distance athletes.
For warm-up areas grass is still, in many instances, the only surface available,
although athletes naturally prefer the same surface as the competition track.
The central arena has always required a surface able to receive and most importantly
dampen the impact of implements whilst minimising the possibility of rebound.
Throughout the developing period of synthetic surfaces and their fore-runners,
unbound mineral surfaces, grass has retained its position as the major acceptablecentral arena surface. Indeed many arena managers require that the central area offers
capacity for alternative sporting events and grass satisfies such requirements admirably.
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Whilst initially there may appear to be many disadvantages in the use of grass forathletic events, the flexibility that this surface offers is substantial. Many sites do
not require, or are unable to provide, permanently marked out facilities for athletics,
for example educational campuses, which because of their hostel accommodationand extensive playing fields, are often utilised for major international events. They
are frequently required to expand their existing athletic facilities out of proportion totheir normal usage. Grass surfaces give this flexibility, combining the all important
training opportunities with scope for setting out tracks for preliminary rounds onareas normally used for other sports.
3.3.1.1 Lifespan
In comparison to other types of athletic surfaces, grass surfaces offer significant
advantages in that, with careful maintenance, they will, at very low capital cost, lasta very long time.
3.3.1.2 Climate
In many parts of the world varieties of grass are substantially different to those inEurope and Northern America. Their use is similar, however, in that they use theirroot system and rhizomes layers to act as soil stabilisers ensuring a firm yet flexible
surface. The grass surface or sward acts as an adjustable running surface that may
be tuned, by adjusting the height at which it is cut, for specific activities.
Specialist construction and irrigation techniques are partly able to alter the firmness
or resilience of the running surface by adjusting the amount of water retained
within the overall construction. Such techniques, often used for American footballand baseball events, indicate the adaptive nature of grass constructions. Grass is
not an “all-weather” surface and is affected by adverse weather conditions. If events
continue under these conditions, the important top running surface and complicatedgrowing medium may be permanently destroyed.
This can require major reinvestment and, more importantly, the loss of substantial
periods of time until the rejuvenated area is again ready for use. Such reestablishment
periods can be as much as six to twelve months depending on climatic and soil conditions.
Differing climates, top soils and subsoils all require differing construction techniques
according to local conditions and no one specification or indeed seed mixture issuitable for worldwide use. In each case the advice of regional sports field construction
experts should be taken.
3.3.1.3 Construction Considerations
The types of grass used should be selected for their surface durability and forsuitability as a stabilising medium. The type chosen for tracks should endure 1.5cm
to 2cm high cutting, and for the in-field 3cm to 4cm high cutting. Careful analysis isnecessary but types used regionally for football or similar activities are often suitable.
One of the most important factors in many grass running surfaces is the drainage.
The capacity to perform during periods of inclement weather is imperative, as heavy
rainfall can quickly turn an idyllic green sward into a wet, muddy and unusable surface.
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TRACK AND FIELD FACILITIES MANUALSports field land drainage techniques have now advanced to the stage where highly
accurate drainage designs can be installed to cater for anticipated rainfall and required
dispersion rates. Although these techniques are commonly utilised on many sports
field activities, additional care is required on their application for athletics.
Such systems often incorporate sand slits or sand grooves to transfer surface
water down and away to subsurface dispersion drains. Unless the grass surface isadequately top dressed with sand and the slits or grooves properly filled at the timeof installation, ruts and trip points may occur through settlement of the sand.
Regular re-application of sand will be required to ensure that good drainage ispreserved and hazards avoided. Such settlements will be especially noticeable inclimates that experience high fluctuations of moisture and temperature causinglarge soil movements through expansion and contraction.
3.3.1.4 Usage
The programming of athletic events on grass surfaces with large numbers ofcompetitors, or over a long period experiencing difficult climatic conditions, can be
crucial. Abuse will often result in a destroyed running surface. This may well be thecase if the grass is poorly laid or not properly maintained. It may be necessary for anumber of preliminary rounds to take place on areas away from the main arena toensure the suitability of the track for the prestigious final events. The programmingof preliminary rounds should, wherever possible, use adjacent grass surfaces thatare still accessible to the viewing spectators.
3.3.1.5 Marking out
In common with all types of tracks not provided with a raised kerb, grass tracks aremeasured in lane one along a theoretical line of running calculated at 0.20m fromthe inside running edge of a marked white line. (See “Construction of the Standard
Oval Track” in Chapter 2). Often plastic road cones or marker flags (inclined towards
the central arena) are provided to visually increase the definition of the inside runningedge. Unless these are provided for the continuous length of the track (they areoften only provided to divert the runner towards the steeplechase water jump) the
0.20m distance continues to be used.
3.3.2 PERFORMANCE REQUIREMENTS
Natural grass should be viewed as the basic surface for athletics. The natural
constraints implicit within its make-up mean that the strict tolerances normallyassociated with synthetic running track surfaces are not fully appropriate.
3.3.2.1 Grass Coverage
Grass must be seen as the top, biological layer of the sports surface and, becauseof its root zone, as the biological stabiliser of the top soil. As for sporting activities
such as football, hockey or cricket the grass surface has to interact with theathletes through their footwear and in addition has to allow the javelin, discus orhammer to travel through the grass sward before embedding itself in the groundbeneath. The movement of a football for example will be affected to a great degreeby the height, density and types of grass present on the playing surface. In thesame way, athletics will be influenced.
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Whilst weed or undesirable plant types can adversely affect the overall appearanceof the running surface they do not always directly interfere with the athlete. It is
important to ensure a good quality surface and to operate the same maintenancemethods as for other sporting grass surfaces. Otherwise undesirable plant types
that may seriously affect the durability of the grass sward will take over.
3.3.2.2 Cutting Height
The grass should be maintained at its most appropriate height (3cm to 4cm) toensure the maximum durability of the running surface. Before a competition, it mustbe cut to 1.5cm to 2cm, in order that it does not physically restrict the progress of theathlete. For a similar reason, excessive grass clippings must be removed.
In order to facilitate the judging in the throws, the grass height in the field should
not exceed 2.5cm.
3.3.2.3 Constructions
The ground or soil structure can significantly affect the athlete in a number of ways.
These are normally through particles of an undesirable size and the flatness of theground (See 3.3.2.4) and as a less durable or excessively soft surface due to theimpermeability of the track’s upper layer rather than the evenness of the height or
the way the grass has been cut.
It is essential that the top layer (root zone of the soil layer) is porous so that excesswater can be carried off into the underlying drainage layer or ground.
This means that the soil layer must be of a suitable composition and thickness.
Moreover, the ground must be sufficiently flat, for example local settling andgrooves must be eliminated. Great care must be taken during construction if both
requirements are to be fulfilled. (See 3.5 for the drainage of excess water.)
For the construction of the grassed surface, the methods explained below arerecommended, and take into account on the porosity of the ground and the extent
of local precipitation.
a)Applicable on sufficiently porous ground for example sand and gravel (Fig 3.3.2.3a).
After creation of the foundation, soil is laid to a uniform depth of 8cm to 12cm.
The bottom of the soil layer is mixed with the surface of the underlying ground to
key the two layers. The soil is then levelled and grass is sown.
b)

Applicable on ground which is less porous yet capable of improvement(Fig 3.3.2.3b).
After creation of the foundation, granular materials (sand, gravel) with particles of
0/2mm to 0/4mm are applied to improve porousness. The necessary quantity
depends on the porosity of the underlying ground.
The ground can then be mixed to a coarse tilth with the layer of granular material.
Pipe drains are then laid at intervals of 4m to 6m according to the porosity of the
improved ground. When the soil is then laid on the improved ground, theperformance of the drains must not be impaired. The soil is laid to a standard depth
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Figure 3.3.2.3a - Method of construction
Example 1: Sufficiently porous subgrade
1 Porous subgrade, 2 preparing of construction ground, 3 applying the grass-supporting layer,
4 loosening/keying, 5 sowing

Figure 3.3.2.3b - Method of construction
Example 2: Less porous subgrade yet capable of improvement
1 Subgrade, 2 drain, 3 preparing of construction ground, 4 applying sand, 5 mixing,
6 applying the grass-supporting layer, 7 mixing/keying, 8 sowingof 8cm to 12cm. After the soil and improved ground have been loosened to key thetwo layers, the soil is levelled and grass is sown.
c)

Applicable on ground capable of improvement for enhanced porosity or loadbearing capacity (Fig 3.3.2.3c and 3.3.2.3d).
This system consists of combined pipe and slit drainage. Slits are installed parallel,
and the drains at 90°, to the layout of the track.
After creation of the foundation, drains are laid at intervals of no more than 12m at
90° to the inside edge of the track (at right-angles to the slits). The drain filling ofgravel or suitable chippings has a particle size similar to that of the slits (See below).
The slit-drains are then created at intervals appropriate to the porosity of the groundand the thickness of the top-soil (usually 1.0m to 1.5m). The slit drains should be 5cm
to 8cm wide and at least 25cm deep, and connected in to the drain runs. The slit
drains are filled with gravel or suitable chippings with a particle size of 2/8mm.
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If necessary, the ground fitted with the combined drainage system may then haveto be worked further. After this the soil is laid to a uniform depth of 8cm to 12cm.
The thickness of the layer depends on the porosity of the underlying ground and the
distance between slits. After the soil and ground are loosened to key them, thesurface is levelled and grass is sown.

Figure 3.3.2.3c - Method of construction
Example 3: Less porous subgrade
Combined slit drain and drainage system - 1 Drain slit, 2 drain, 3 pitch

Figure 3.3.2.3d - Method of construction
Example 3: Less porous subgrade
Combined slit drain and drainage system - 1 Subgrade, 2 drain slit , 3 applying the grass-supporting
layer, 4 mixing/keying, 5 sowing

Ground of insufficient load-bearing capacity must be stabilised before installation of
the drainage system.
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TRACK AND FIELD FACILITIES MANUALd)Applicable on ground of insufficient porosity and limited capacity for
improvement, e.g. water-sensitive or unstable ground, rock, or in areas of highprecipitation and valley sites at risk from flooding (Fig 3.3.2.3e).
After creating the foundation, drains are laid at intervals of 5m to 8m depending on
the porosity of the ground. The drainage layer is then applied to a uniform depth of
12cm to 15cm. After this the soil is laid, also to a uniform depth of 12cm to 15cm.
After mixing the soil with the drainage layer to key them, the surface is levelled andgrass is sown.
The maintenance of athletics facilities is described in Chapter 7. In addition, attention
has to be directed to checks that must be undertaken to remove all stones prior to
the surface’s use for athletic events. The presence of such stones would adversely
affect an athlete’s spikes or create a hazard by deflecting a field event implement.

Figure 3.3.2.3e - Method of construction
Example 4: Subgrade with insufficient porosity and limited capacity for improvement
1 Subgrade, 2 drain, 3 drainage layer
4 applying the grass-supporting layer, 5 loosening/keying, 6 sowing

3.3.2.4 Flatness
The overall gradient tolerances of IAAF Rules shall be adhered to. However theflatness of the grass surface cannot be to the same tolerances as synthetic
surfaces. Settlement, maintenance operations such as spiking and slitting and theimportant additions of top dressings will all result in minor local differences of level.
However, reasonable tolerances are achievable and must be observed to remove
trip hazards and problems of water ponding.
On a localised level there shall be no bumps or depressions beneath a 3m straightedge exceeding 10mm, and beneath a 0.50m straight edge exceeding 8mm.
Surface changes caused by the actions of burrowing animals, worms or insects
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C hapte r 3 - C ons truc tion of the Trac kshall be “made good” prior to any athletic event. It must always be recognised
however that many such actions have important and beneficial effects upon theoverall soil structure and are therefore necessary to promote good grass growth.
3.3.2.5 Thickness
The upper layer should have a minimum consolidated depth of 8cm prior to seeding,turfing or commencement of the grass layer. This is necessary to ensure good root
establishment, ground stability and penetration of the spike of the athletes’ shoe
without meeting any solid item.
3.3.2.6 Drainage
The recommendations and proposals in Sections 3.5 and 3.6 will enable the facility
to meet the IAAF Specification for synthetic tracks, that no standing water should
be present twenty minutes after rainfall has stopped.
This requirement is normally achievable with natural grass.
3.3.3 TESTING
Some of the dynamic tests which have been developed can be applied tonatural grass surfaces, and there are proprietary items of equipment which have beendeveloped for such ground, in the form of “impact hammers” which give readingsof loading and penetration of test cylinders into the surface. However,theseprocedures have not been routinely applied to natural grass for athletics tracks, and
it is not possible therefore, at this stage, to define their use or set limits for the various
surface characteristics which they measure.

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7.2.3 NATURAL GRASS SURFACED TRACKS
7.2.3.1 General Aspects
Natural grass surfaces are mainly used for infield throwing events. However, they
can be used for tracks. Turf requires specialist care. Since it is a living material,
particular attention must be paid to the frequency of use.
7.2.3.2 Suitable Equipment
For normal maintenance, the following equipment is required:tractorride-on grass-cutter
nutrient spreader
sand spreader
seed spreader
hand tools
renovation equipment
For renovation, the following equipment is recommended:
top dresser
airifyer/aerator with slices/pipes
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Chapter 7 - Maintenance7.2.3.3 Necessary Materials
The following materials must be available:
substitute grass areaseeds
nutrients
sand in specific gradients
growth medium of standardised quality
7.2.3.4 Required Properties of the Surface
The most important factors are: evenness, compactness, growth and height of grass.
7.2.3.5 Regular Procedure
A natural grass surface should be inspected daily. The normal procedure consists of
cutting and watering (frequency varies) and repair of the surface, when necessary.
7.2.3.6 Basic Procedure
The following main tasks should be undertaken in a basic maintenance plan:
When mowing, the cutting height must take into consideration the sports activities
for which the surface will be used. Prior to a track and field competition the grassshould be cut to 1.5cm to 2cm in height.
All grass cuttings should be removed, ensuring they are not spilt onto a synthetic or
unbound mineral surface.
A quantity, quality and time programme of nutrition must be established.
For watering, flush sprinklers are recommended.
Local damage must be repaired immediately. All thatches are to be removed.
When necessary, the surface must be loosened with special tools and sanded with
0.2mm to 0.4mm particles. Leaves, litter and other deposits are to be removed.
Plant protection must be observed in accordance with national law.
7.2.3.7 Seasonal Works
The seasonal preparation of the grass surface is of great importance. Plans shouldbe established for Spring works (general preparation), Autumn works and maintenanceafter each training session.
7.2.3.8 Restrictions on Use
Natural grass must be protected. The frequency of use must be regulated andsufficient time allowed for growth and maintenance (repair of bad spots, generaltreatment, renovation). The surface should be protected from heavy vehicles.
For the hammer event, the surface should only be used for competition and not for training.
The inside lane should be closed for training using barriers.
7.2.3.9 Regeneration/Renewing
Even with well planned and practiced maintenance, a natural grass surface will
require a carefully planned regeneration after 6 to 10 years. Based on analysis of
the growth medium, compactness, porousness and the condition of the grass,there are different principles for regeneration or renewing.
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Simple surface renovation
This method is recommended as a natural renovation for uneven surfaces oflarge areas of worn grass.
The procedure consists of cutting the grass 1cm, verticutting for cleaning thesurface and removal of dead grass and thereafter levelling with growthmaterial. It is important that all compact areas are loosened. This is followed
by a top dressing of sand and, finally, overseeding.

-

Combined surface and depth renovation
To be used in cases of greater compactions, bad drainage and poor grass cover.
The surface should be cut, cleaned and levelled. In addition, it should bevertidrained to a depth of 15cm to 30cm before sanding and overseeding.

-Renewing
This procedure is to be recommended in acute circumstances. The grasssurface may be waterfilled due to compaction. The procedure for renewing is
the removal of the top layer of approximately 5cm. The drainage must be
inspected and, if necessary, renewed. The ground should be loosened andlevelled with granular materials to the required standard consistency.
New soil of a standardised sand-based composition should be laid to a depthof 8cm to 12cm. This soil should be levelled and seeded.

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