St Andrews Links Blog

Bunker improvements at The Castle Course

After maintaining the greens, bunkers can take up the largest amount of man hours. It generally takes three team members 3.5-4 hours each day to rake them. Over a week, this can be roughly 80 hours – a lot of effort for a hazard!

Problems we face with The Castle bunkers:

• Wind: The site is extremely exposed and unlike the pot bunkers on our other six courses, the sand can be blown about quite easily.
• Contamination from the sub-soil: As the course matures, stones have started to come up through the subsoil accelerated by rabbits digging in the faces.
• Wash damage from heavy rain: When the course is hit with extremely heavy rain, the sand washes away from the heavier sub base along with fine silts and clays causing more contamination.

When we get high winds or wash damage we might need to put the whole team out to get the bunkers in a decent condition for golf. Last year we did a trial of various bunker liners to help prevent this. Materials included were:

• Glued gravel layer
• Tarmac
• Concreted gravel layer
• Rubber matting
• Upside down turf

In the end we felt the glued gravel worked best.

Installation

The process of installing this new liner involved initially scraping out the existing sand and re-shaping the base to accommodate the gravel layer.

Sand and base layer being shaped

Once done, we needed to check the drainage to see if it was working correctly and make any necessary repairs. When we were happy with this element, we started pouring in the gravel.

Pouring in the gravel

This is then spread out across the bunkers to a minimum of 50mm. To measure this, we used 50mm pipe cut into small sections placed around the bunker to give us a consistent depth. If less than 50mm, the bunker liner wouldn’t work correctly.

50mm pipe used for consistent depth of gravel

Once the gravel was at a consistent depth across the bunker base it needed to dry to a moisture content of less than 7% for the glue to work. Being in Scotland, this was a bit of a waiting game! When at the correct moisture level, we gave the gravel a final rake and sprayed it with glue that was warmed up over a few days.

Final rake and glue being sprayed onto the gravel

The idea is the glue sticks the first 25mm of gravel but the remainder underneath stays loose to help aid with drainage after heavy rainfall and allows the glued layer some flexibility. After 24 hours, each bunker is inspected to make sure the gravel is firm enough. Any areas needing more glue were circled and once happy we ticked the bunker to show it was complete!

Bunker with a tick ready for sand to be added

It was then a matter of filling the bunkers back up with sand ready for play. We aim for 100mm of sand on bunker faces and 100-125mm in the bases. This is checked by dipping into the sand to the correct depth. As the sand settles over time, we may need to re-check the levels. We don’t want golfers hitting the gravel with their clubs.

Filling bunkers

Dipping to check sand levels

The benefit of using a gravel layer and this depth of sand is moisture is held in the sand just below the surface so on those windy days it’s less likely to move about allowing the greenkeeping team more time to do other tasks around the golf course.

So, as ever, happy golfing and hopefully you won’t find yourself in too many of our newly improved bunkers!

Words by Jon Wood, Course Manager – The Castle Course