Bunker Sand Analysis

Selecting the best sand for our Bunkers…

“Playing quality is unquestionably the most subjective parameter when choosing bunker sand. The most important component in the selection process is allowing an adequate amount of time to fully evaluate the various factors.” - James Francis Moore

With the exception of greens…bunkers and the sand in them, are probably the most controversial and discussed features on golf courses regardless of the golfer's ability.

The composition of the sand strongly impacts on maintenance regimes and playing quality.

These are the five most important factors that we had to consider before selecting the sand for our bunkers.

• Particle size
• Particle shape
• Infiltration rate
• Colour
• Overall playing quality

Different suppliers in South Africa were contacted to supply samples and descriptions of their bunker sand mix including detailed specification of particles sizes and percentages of the finer granules so to determine if they conform to the USGA Specification Standards used on almost all golf courses worldwide. Below follows a table comparing the USGA specs and PCC bunker sand composition.

Fraction	Size (mm)	Bunker Sand (% of each in mix)	USGA Recommended Mix (% of each in 100% mix)	PCC Prescription Mix (% of each in 100% mix)
Gravel	>2	< 3%	0	0
Very Coarse Sand	1-2	> 15%	2.3	3.8
Coarse sand Medium sand	0.5 -1.00 0.25 – 0.5	> 65%	84.7	84.9
Fine sand Very fine sand	0.15 – 0.25 0.10 – 0.15	< 25%	12.8	11
Silt	0.002 – 0.05	< 3%	2	0.3
Very fine silt, sand, clay etc.	<0.10	<1%	0.2	0.3

Particle Size

As a general guideline, sand used in bunkers should be composed of particles with a large majority in the range of 0.25-1.00mm. Silt and clay (particles below 0.05mm) should be kept to a minimum. In other words, it is unlikely that sand that falls significantly outside this range will perform well in terms of crusting, firmness, porosity and/or playing quality.

Particles greater than 2.00mm are classified as gravel. If present in large quantities, particles in this range damage mowing equipment and cause the ball to deflect off line on the putting surface.

Particle Shape

The shape of the sand particles has a strong influence on playing quality and maintenance. A sand particle's shape is classified by examining both the relative sharpness of the particle's edges and the overall shape of the particle itself.

Infiltration Rate

Infiltration rate refers to the sand's ability to drain.  As a general guideline, sand being considered for use in bunkers should drain at a minimum rate of 500mm (20 inches) per hour.

The sand in the old design bunkers gradually became contaminated with the clay soil from the base and sides of the bunker and subsequent high clay content prevented proper drainage. In the new bunkers we installed Bunkermat® which is a carpet-like lining that prevents contamination of the clay/sand from the bunker base. Similarly the grass covered bunker faces prevents contamination from the bunker walls/sides.

This photo taken on Hole #15 at PCC in March 2012 with the old design bunkers, clearly shows the poor drainage and infiltration rate of rain water through the sand.

Colour

As a general rule, lighter coloured sands are preferred since they contrast beautifully with the green grass. Due to dust and organic particles blown in by the wind the white colour of the sand rarely last more than 6 months or so before turning to a more natural brown/tan colour. An annual program on many courses is to add 50- 150mm of sand to existing bunkers to replace what is lost from explosion-type shots, water and wind erosion.

Overall Playing Quality

Without question, playing quality is the most subjective evaluation of bunker sands. Players vary widely in their assessment of what constitutes good playing quality. One of the few shared opinions seems to be a desire for all the bunkers on the course to play in a consistent manner.

The other factors that influence playing quality and have nothing to do with the composition of the sand include:

• Raking frequency and methods
• Irrigation coverage and frequency
• Depth of the sand
• Duration the sand has been in the bunker
• Maintenance practices

Conclusion

There is indeed more to selecting the right sand for our bunkers and today's golfers are becoming increasingly more demanding for bunkers to play consistently, drain rapidly and provide aesthetical value to the course.

This was why we constructed and used test bunkers prior to the Re-design Project to allow golfers to evaluate the different sands for playing quality before making a choice that we might have come to regret a few years from now.

Finally, time will be required for the newly installed sand to firm up and take on its final playing characteristics.

References:
 James Francis Moore from www.USGA.org - Green Section Record Jan/Feb 1998 Vol. 36, #1