Bunker Edges - Maintaining integrity

Richard Allenin Technical

I clearly remember 1976, the last time we experienced a summer like this in Britain. After many years of wet summers, how are our golf courses coping with such a dry one? Fortunately, widespread water usage restrictions haven't yet been imposed.

On my travels around the country, and watching the tremendous recent Open at Carnoustie, it seems that putting surfaces are generally well kept with adequate water. Fairways and tees, by contrast, are providing challenging and interesting conditions for golfers - my own course, Southerndown, being a great example - and, no doubt, seed houses will be busy this autumn, as overseeding becomes an important recovery task.

But what about bunkers, the source of my livelihood over the past few years? I've had many discussions with greenkeepers and other golfers over the past few weeks, and the main topics can be divided into two areas of concern: maintenance and playability.

Over the past few summers, bunker wash outs have been a significant drain on maintenance resources. Though I am sure there will be thunderstorms this summer, the challenges during a prolonged hot and dry spell are different: dried out, crumbing edges and faces (maintenance) and super-dry sand increasing the potential for plugged lies (playability). What can course managers do to address these issues?

The resilience of edges was the issue that first drew me into bunker construction work. I wonder if the following short anecdote rings true with many golfers and those brave enough to sit on a greens committee?

Eleven years ago, I was a member at an established Colt designed course in South Wales. I wasn't involved with the greens committee, but I had previous experience as a greens chairman and various golf course design and construction projects. By no means an expert (I was from a civil engineering background with little agronomic experience), I was keen to learn more about how golf courses are designed, built and maintained. Consequently, when the golf course began to replace its 'sharp', high edged irregular bunkers with rolled in mowable surrounds I wanted to know why.

I was initially told that the edges and faces were too expensive to maintain. After I asked (as politely as I could) if there were any other options that could retain the old Colt styling, I was rather bluntly told to 'mind my own business'. At the time, it was a very frustrating experience, and I resigned from that club at the end of that year but, looking back, I must be thankful to the greens committee there. The process I went through left me utterly determined to find a solution that could have saved the shape of those bunkers and started me on a completely different and exhilarating career path.

The first results of my research were surprising. Back in 2007, there were quite a few under-sand bunker liner products on the market. Brand names like Sandtrapper and Terram were found, but there was nothing in the golf amenity sales sector that could be used to stabilise bunker edges. I looked into the world of civil engineering and soil mechanics where I was very comfortable.

Although there is a vast array of membranes, geotextiles, soil hardeners and other erosion control products, I could not find any solution that could deliver the essential combination of natural aesthetics and robust construction. Then the solution presented itself to me in surprising circumstances.

Late one winter night, getting in my car to drive home from a meeting, I turned on the headlights, which shone across the car park. Straight onto a roll of used astroturf carpet, which was angled end-on towards me. What I saw at that moment (a natural looking layered turf effect) was the culmination of many months of research.

Left: Typical Drought Damaged Bunker Edge. Right: Rubber Crumb Liner Exposed

It prompted the invention of a new bunker edging system which is now being used worldwide on some of the best-known golf courses; protecting bunker edges from Category 5 hurricanes, six month Arctic winters and everything in between. So, what effect is artificial grass edging having on bunkers during the current extreme dry conditions in the UK?

It's relatively simple to explain. Without living grass coverage, and the healthy root structure, most soils are highly vulnerable to erosion. On the golf course, it is bunker edges where the effects of erosion are the greatest. They tend to be more exposed to wind, sun, freeze-thaw cycles and heavy rain, and they are constantly being impacted by clubs, balls and foot traffic. Some edges, because of the particular bunker design style, are exposed soil surfaces. And, of course, all steep banks are a magnet for burrowing animals. In these conditions, bunker edges quickly deteriorate. The two main consequences are sand contamination (everything from silt to fist sized stones) and ugly aesthetics.

Contamination will lead to inconsistent playing conditions, reduced drainage potential, damaged golf clubs and, where stones and gravel are thrown out onto mowable areas, expensive cutting blades can be damaged. Stone picking, de-silting blocked drainage and sand replacement is time consuming and expensive. Quality bunker sand is not getting any cheaper.

Eroded edges may suit the aesthetics (for a while, before they get out of control) of some golf courses, but most golfers - the paying customers - rightly or wrongly, expect a more manicured and maintained appearance.

Left: Bunker Edges Benefitting From EcoBunker Sub Soil Irrigation At Denham. Right: Bunker construction at St Leon Rot

Greenkeeping professionals also have great pride in their golf courses and don't want to lose control of bunker edges.

Typically, 'half-moon edging' has been the preferred technique for tidying up bunker edges. However, this again is time consuming and it usually leads to an incremental loss of the original bunker shape (which can negatively affect aesthetics and strategy). It is also very easy to introduce more sand contamination during the process and, as we shall see, where bunker liners are already in place, it is a practice that should be avoided.

Bunker liners are becoming widespread as more golf clubs begin to understand the benefits they bring. However, if a bunker liner is installed without attention to the edge detail, this can lead to big problems down the line. We have seen many issues, although one of the worst effects is when 'half moon edging' takes the bunker edge outside the line of the buried bunker liner. This will, in almost every instance, permit sand to penetrate underneath. Soon, liners will reach the surface, and a complete reconstruction will be urgently needed. The photograph above shows the effect of bunker edging over an expensive rubber crumb liner at one of the golf clubs where we were invited to provide advice and assistance.

Where bunker liners are used, edge maintenance should be undertaken with more care. Options are limited. Therefore, it is highly advisable to consider future maintenance when selecting the construction detail for bunker edges.

Revetting, using thick cut, custom produced natural turf, is very popular. However, this is not a permanent solution and, on average, will have to be completely rebuilt every four or five years (and sometimes more regularly on exposed south facing edges). As it is natural turf, it is of course also vulnerable to drought and we have seen many natural edged bunkers struggling over the past few weeks.

A good alternative to natural turf revetting is artificial turf revetting. The facts that it needs very little maintenance and that it won't have to be rebuilt for at least a 20-year period are widely understood by now.

It is not significantly more expensive than natural turf and whole life costings typically show a full return on investment (ROI) within five to seven years and, thereafter, major cost benefits for another fifteen years and more.

In the current conditions, tall bunker edges can be vulnerable to drought conditions.

At EcoBunker, we cannot claim to have predicted the current summer, but we have, over the past four years, been developing and installing drought resilient technology into our main bunker edging systems. It is excellent timing for us as we now have the ultimate test of the effectiveness of our latest innovation.

Since the foundation of the company in 2014, my team and I have continually been looking at ways of improving our products and services. I think this is simply a habit shared with similar minded 'techy' engineering types.

One area for improvement was increasing the drought resilience of our system. After doing lots of research, and several trials of different techniques, the use of sub surface driplines began to emerge as a strong contender. One of the problems with so called 'leaky pipe' irrigation technology is that it doesn't work well under the soil. We wanted an irrigation system that provided moisture from below (by far the most water efficient method) but, if traditional leaky pipes are used, they tend to clog up within a year or two as grass roots penetrate the tiny apertures. Then our research found Rain Bird's XFS system, specifically designed for undersoil use. The patented water emitters have a unique copper insert which deters roots from penetrating.

Rain Bird were excellent to deal with and surprisingly confirmed that we were the first company to suggest using the XFS system (which was developed originally for landscaping and gardening applications) in the golf sector. For the past twelve months, we have worked in partnership with them and have been offering the dripline as a standard install upgrade option with our bunker edging systems. It's worth noting that, to be effective, the XFS needs to be bedded on something firm and stable, and the stacked artificial grass wall provides this platform. So how has the system been performing?

Recent photos, taken at Denham Golf Club in West London, clearly show how the turf around the bunkers we installed last winter on the first and eleventh holes is coping with the drought.

Normally, during dry weather, bunker edges tend to brown off before the surrounds. In the photo left, it is very interesting to note how the bunker edges (which benefit from the new system) are actually greener than the adjacent rough and fairway. The ultimate plan, wherever practicable, is to connect groups of bunkers to the pressurised irrigation network and use solenoid valves to enable the course manager to take full interactive control over them. The system uses water in a very sustainable and efficient manner, and we are very excited about the prospect of providing a very effective solution for many golf courses in the UK.

Before concluding, it is also worth commenting on the effect of super-dry sand on playability. I've seen lots of social media complaints about plugged lies in bunkers, along with comments about the sand being too deep, or the wrong type, or uncompacted. I am a keen golfer, and I've had an increased incidence of plugged lies recently, but I feel that I have to support greenkeepers here.

Golf clubs, understandably perhaps, are nervous of taking a strong line with members and standing by the principles of 'play it as it lies' and 'nobody has a right to a great lie' and an 'automatic line straight to the flag'. Super dry sand is weak. There is no moisture within the intraparticle voids which is essential to generate strength via the cohesive and adhesive forces.

There are sensible measures that can be taken to reduce the potential for plugging; for example, it is always wise to check the sand grading curves (they should be provided by suppliers) and the sand particle shape which should feature more angular grains. One of our services is sand grading analysis and, on occasions, we have found sand to be 'less than perfect'.

However, this summer, perfect bunker conditions are very difficult to deliver and all we can do is provide our committed greenkeepers with the tools and let them do what they do best.

We all know that amateurs like to emulate the professionals. Wouldn't it be refreshing to see amateur golfers accept those challenging bunker lies just like the professionals did during the wonderful Open at Carnoustie? I didn't once hear the depressing cry 'get in the sand' and it was great to see the bunkers gaining respect for what they are. Hazards!


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