shaped to collect water for drainage. A significant problem for bunkers is that of drainage, which must be high priority if the bunker is to remain in play through very wet weather. Drain lines should be installed centrally in a drain trench, having a uniform fall of at least 1 in 200 to connect with a suitable outlet. Bunkers can be drained to a sump point or soakaway, but only if the lower soil profile has good drainage characteristics. There is little point in putting in a soakaway which quickly fills up and the area becomes a pond.
Traditionally, the drain trench is backfilled with clean, hard aggregate of 8-10mm diameter to within 50mm of the bunker floor. To prevent migration of sand particles into the aggregate, a blinding layer of coarse grit can be laid over the gravel, level with the bunker floor. Alternative methods of blinding are the use of upturned thatchy turf which creates an excellent barrier to sand infiltration into the drains, or one of the newer imports from the US (Sand Trapper) which creates a barrier to backfill contamination while allowing the sand to bed in.
• Within the bunker design, greenside bunkers should be set back from the green to reduce problems associated with sand splash. In theory, the
bunkers should be shaped to allow the ball to be collected within the back two-thirds of the bunker so that any sand splashed will be collected in the bunker itself.
• The general shape and size of the bunker must be in keeping with the hole. It is at this point where the employment of a golf course architect would be beneficial to advise the club on a professional basis. Repositioning of bunkers needs careful thought and must be sympathetic to the original architecture.
Bunker sand
One of the most contentious subjects with bunkers is the choice of sand. There is no perfect formula and the final choice is generally a compromise between the material having suitable particle size, shape, colour, freedom from lime and cost. If a bunker is to provide a fair hazard, it is important that, when a ball lands in the sand, the surface is neither so hard that a ball bounces out or rolls, nor too soft that the ball plugs to an excessive depth. The sand should be stable under foot and of a consistent depth. Specifications to meet the above requirements have been developed in the United States and trials carried out at STRI merely confirm these figures to be acceptable.
The recommendations state that sands are required to have 95% of their particles between 0.125 and 1mm diameter range, with the majority of particles falling between 0.25 and 0.5mm diameter. This is not to say that any sand which falls within this range will be excellent bunker sand. What it does indicate is that sand falling within this range will have a better chance of being a good bunker sand rather than one that falls outside this range. Particle sizes larger than 1mm can have problems associated with blunting of mowers etc., and a large amount of particle sizes below 0.25mm are prone to wind blow and can restrict drainage movement.
Consistency of playing characteristics between the bunkers, which can only be achieved by using the same sand in each bunker and for topping-up purposes, is essential. Where different sands are used to top-up, this can lead to variations in playing characteristic and, therefore, consistency is lost. One of the main reasons for compiling this article is to raise awareness in respect of bunker sands that will no longer be available in the future, and alternatives will need to be found. The very popular Moneystone bunker sand (WBB Minerals) will not be available within the next two years and PS White (Banks Amenity) is now
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