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

PCC Bunker Re-Design

Bunker Re-Design Project 2012

A few years ago we decide to have a good look at the option of re-doing our Bunkers here at PCC. 

The pot-style bunkers were not just difficult to play from, but they were becoming very inconsistent and an in-depth investigation started to calculate if these high costs of maintaining them was actually still worth it...

Why did Pretoria Country Club decide to change their Bunkers?

The pot-style revetted bunkers were introduced to the Pretoria Country Club in 2004 and were designed by the Gary Player Group.  It is now eight years later, and the committee had to address various course architectual matters as well as strategic matters relating to the pot-style bunkers with the geo-textile bunker faces to ensure that the bunkers performed with consistency after the refurbishment.  Golf course architectual matters included: Ensuring good drainage, replacement of bunker linings, reduction of sand contamination, removing clay basis, removal of deteriorated bunker faces and finding a solution for inconsistent bunker sand.  Strategic matters included: Overall playability, addressing members’ complaints, adapting to technology changes, ensuring that the Pretoria Country Club’s golf course remain unique, improving the course ranking, retaining the Gary Player signature and ensuring adherence to the Pretoria Country Club’s long term Strategic Plan.

 Why were they in desperate need of change?

The main problems were poor drainage (the clay soil made its way to the drainage systems under the bunkers and these clay particles would eventually bind with the silica sand and started to clog and block up the drainage pipes, thus not allowing these bunkers to drain quickly after a rainstorm), inconsistent bunker sand, deterioration of many of the geo-textile bunker faces, contamination of bunker sand and playability had to be addressed.

 All the above resulted in excessive maintenance to be done on a daily basis to prepare these bunkers before play every morning which became almost impossible.

Drainage problems was one of the main reasons to reconsider the future of this style of bunkers on PCC.

 What has changed and how are they different from the old ones?

The vertical geo-textile faces and material were completely removed on all 86 bunkers and the angle of the bunker faces was reduced to between 30 and 35 degrees to allow for the planting of sods. The new faces were all planted with Tiffsport (Cynodon transvaalensis & Cynodon dactylon hybrid) the main reason being the colour difference which had to be created between the Kikuyu fairways and the Cynodon bunkers for visibility purposes. The Tiffsport is a finer leafed specie and much darker in colour than the Kikuyu surrounds and this will create a definite contrast between the surrounds and new bunker faces.

With the vertical bunker faces being removed, the new angled faces will be more forgiving for less than perfect bunker shots.

We have also done extensive testing in our trail bunkers to determine which type of sand would ensure the best consistency.  The solution was the perfect mix of fine sand particles and bigger sand granules which complies with USGA Bunker Sand specifications.

 What goes into changing Bunkers, who would be involved and what was the duration of the Project?

The initial investigations started in December 2010 by the golf committee to identify all the problem areas.  During the period January to August 2011 the golf and greens committees consulted with various experts to obtain all the relevant information relating to which options were available to upgrade the bunkers.  After approving the first proposal the main committee approved the construction of two test bunkers (one fairway bunker and one greens bunker) to allow members the opportunity to comment on the proposed changes.  Various forums were held to inform stakeholders what the proposed changes would entail, these included ex- chairmen and ex-golf captains of the club. We further consulted with Gary Player to obtain his approval to ensure that we retain the Gary Player Signature after the refurbishment of the bunkers.  After final approval in June by the main committee, the course designers, DDV Design Group and the main contractor, Life Sports Turf were appointed.  The project started in July 2012 to ensure that it would be completed by end October and in time for the growing season.

What feedback and comments have you received so far?

Feedback from members, visitors, ex-chairmen, ex-golf captains, our golf directors and other interested parties are extremely positive.

 People sometimes get the wrong impression of bunkers and see them as just a hole in the ground with sand in - What technical aspects do the bunkers need to comply with?

Well once again it is clear that sand consistency and presentation are the two main factors. Sand consistency can not be achieved without proper drainage. The underground drainage should be able to drain the water as quick as possible so the sand can dry out and be ready for play almost right away. The type of sand also plays a big role as your percentage of fines should not be more than your bigger particles as these will cause compaction and also slow down the water movement. The sand can also not be to loose as this will almost certainly cause a “fried-egg” lie every time a ball plunges in it. The success of the project and our bunkers will depend on the day-to-day maintenance of them and make sure they not just look good…but play even better.

How much did the Project cost?

The total cost of the refurbishment of the 86 bunkers and the various other improvements that were made cost in the region of R1,700,000.