Barry Pace, Contracts Manager for Speedcut Contractors offers, what he calls, 'A Fools Guide to Bunker Liners'. In this article, he explains the various options available, discusses the success rates and looks at some of the pitfalls that await the unsuspecting. The bottom line to ask yourself is, do you need to line at all?
In this article, I have tried to be as objective as possible with the actual products or solutions to give as fair a summary as I can but, as much of what I think comes from twenty-seven odd years of actually watching, seeing and doing 'golf', then some subjectivity may creep in.
I have also ignored drainage as, regardless of the chosen option, an adequate piped or soakaway drainage system in place should be a given for any bunker project to succeed.
So, the first question really is; "do you really need to line?", and that answer can only come from you as the specifier or the client in terms of what is available to spend and what is wished to be achieved, perceptions, expectations and, of course, site conditions.
So, here are my initial thoughts on why you would line - playability, durability, longevity, and consistency (the last one could explode a discussion for ever, so I will leave it there).
But, in reality to:
- prevent/reduce vermin damage to bases
- prevent/reduce stone contamination
- prevent/reduce wash down of faces
- prevent/reduce silt and clay contamination and to improve drainage
- reduce labour inputs
- reduce sand replacement costs and extend sand lifespan
- prevent/reduce the migration of sand areas towards a green
And why you maybe do not need to line:
- natural sand subsoil
- stable, stone free subsoils
- shallow sand faces with minimal erosion factors
The Natural Way
So, assuming you do not have a site with perfect stone free, stable soils or subsoils that will not erode, plus enough staff to keep sand depths consistent, the first option is the old school way, which has always been to use upside down or up grown turf.
My preference has always been to use the nastiest, oldest, wiriest turf you can find on the course, but logistics and availability are invariably the downfall of this, along with time to bed in. New 'standard' turf to me is a completely false expense as it neither provides any durability nor life, especially if it is a 'busy' bunker.
Some of the new 'thick' or revet turfs will do a job, but the square metreage costs need considering; high spec turf doesn't come cheap.
If you have time, 'grow-in' is an excellent option, allowing the turf to really bite down before spraying off just before sanding, but time is key for green side up, I think.
I have recently seen some similar 'installations' in the UK where the whole bunker has been turfed, but they seem to have missed out the ledge bit! I do not know what happens when you go to sand up and, no, they were not hollows.
I have also, in the distant past, seeded through bunkers on full builds to establish as grass initially but, again, the scrape out and bowl preparation negates any gain, I think, with the important face edge where a lot of the issues come from being bare soil at sanding.
The next option is to remove a depth of 'nasty' soil and replace it with some nice clean sandy material. Again, I have done this in the distant past but, unless you have pockets of perfect soil actually on site, or cheap nearby, the costs and logistics may far outweigh any actual benefit.
If I was 'spoilt' for material, I would seriously consider this though.
Another variant, and successful at a few courses, is to use a path type aggregate cap to similarly blind out the base, but the real limitations of this are angle of slope and depth management to prevent this eroding out or up. It works well on downland with flat sand areas and big flints for a few in UK. Its use would be very limited if you have any form of sloped faces, I feel.
Polymer type Spray Stabilised Soils and Aggregate Bases
To evolve from the above, there are three versions that crop up; Klingstone, a US company with a long standing history, but I have zero knowledge or experience to comment beyond that they are still there doing what they do; Stalok; which showed up on a brief Google search - again, I can make no comment; and Better Billy Bunker, which has been used on a few sites in the UK with significant numbers of 'happy customers', including a good few 'notables'.
I look forward to being convinced of this method's merits and durability given the 'notables' who obviously are extremely pleased with its performance.
I first came across a Soil Spray Polymer type system about fifteen years ago and can remember being asked to go down to Bristol to look at a new revolutionary system being installed. I got as far as Reading on the M4 when a call came in to say "don't bother, it's all gone off in the pipe and barrel!" The UK weather got the better of that early version.
In the recent past, we also had in the UK an infamous Aggregate Spray Lining System that promised the world, with guarantees, top track endorsements and fancy brochures. It wasn't all it was meant to be with alleged poor application, failures, flaking and breaking out. My company did two bunkers for one course and vowed never to touch it again.
I believe that most of the places it was used at have replaced it by now and this has made me extremely sceptical about spray applied solutions, but the current 'brand leaders' have an excellent and growing portfolio and it may be that the changes to aggregate size, materials and application are enough to make this work. I look forward to seeing for myself.
And so to the 'Engineered Solutions'
The Engineered Solutions can be split into three sub-categories - porous tarmacadam, porous concrete and porous rubber.
Tarmacadam Liners are a layer of hot laid open texture tarmacadam that is stable, semi flexible and extremely porous, so giving good drainage capabilities, with the surface texture able to 'hold' sand in place.
In the UK, it was developed at The Wisley by Topsport and has been in use and trialled for over five years. A search shows Matrix and Proline as being other variants.
Concrete Liners are, similarly, a layer of specially formulated open textured concrete, generally batch mixed on site, that is a little more than normal concrete.
The two main players are Capillary Concrete, which uses a special aggregate and cement mixture, and DAR Golf Construction from Ireland who offer SportBond bunker liner using, what appears to be, standard aggregates with a special admixture. Both use onsite mixing set ups.
These look simple enough to install.
Rubber type linings systems tend to be a layer of wet poured rubber crumb or chip laid over an aggregate sub-base of varying depths. The benefit this has over the alternatives above is the impact resistance of the surface should sand levels become too thin.
The world leader is Blinder, but a few others have cropped up now to include Bunker Base, Bunker Bond and a pre-made mat type called Polylast.
Possibly the most expensive per square metre due to material costs, rubber isn't cheap, but seen as the performance leader.
Geotextile and Sheet Liners
All variants of a geomembrane type material are mainly pinned down using soil staples and, being a textured material, will help 'hold' the sand and provide a durable barrier.
The list includes SandMat, BunkerMat, Sand Trapper, Sand Catcher, TrapTex, and a UK product called Hyline that is a self-weighted composite three layer material.
My knowledge of these in terms of performance is fairly limited, to be honest, as I have tended to keep away from pinned materials due to concerns over 'pin lift' but, with any liner, slope angle, sand grading and shape will affect how well they work.
I have, in the past, supplied and/or installed 250g/m2 thick geotextile underlays, but these really have slope limitations and are durable barriers for flatter sand areas only.
Several clubs have, and are, using 'recycled' sand filled MUGA/Hockey type carpets to line bases similar to the membranes above, pinning slabs to cover the areas. Again, like natural turf, some are going pile up or back up, depending on personal views.
For new carpet products in the US, there is Bunker Solutions that use an enclosed white carpet, drainage base and edging system where the bunker drain pipe is set above the liner.
In the UK, there are a couple of options. One from County Sports Surfaces has a short, dense pile product and a new material V-line from Verde Sports which uses a white porous 20mm pile carpet.
With all carpet type systems, if installed right, these can be fully jointed and glued for integrity.
A good few years ago, we did some early trials after a canny course manager said he was going to line his flinty bunkers with old hockey turf. We had two courses where this was installed to trial on bunkers for over two years and it did perform well enough, but the logistics, the fact that the material was really 'end of life', in bunker handling issues and getting a neat finish meant we did not pursue the 'old turf' option.
It should be noted and considered that, whilst the surface of carpets are fully UV stable, the base or backing often is not and a lot of this material is sat rolled up in the sun degrading. From a contractors point of view, this really is a little too risky to promote, even if it was easier to do.
The choices are getting extensive now, with several similar variations of the specialist or original brand type cropping up, so I revert back to the first real question; if you really need to line, then you have to pick out what is going to work out best for you on your site with your soil, bunker style and prevailing weather conditions.
But is that the whole answer? No, I really do not think so. Two very important additional questions need to be asked.
Sand Choice: These nice new bunkers with nice new sand - normally sourced from the good old place you have always got sand from because the members 'like' the colour - will probably play rubbish for years in the summer due to plugging in fried egg lies as the contamination you have sorted out was, for a time, actually what 'glued' the sand together a little in its early days (post settling).
Some greenkeepers are playing with sprinklers and adding fine sands or layering sands to mitigate this.
In the UK, we are becoming increasingly limited in sand choice and selection and it is an expense that can make or break a project.
Similarly, with the lack of contaminants, some of the more common sands can suffer wind blow, even on an inland location, as the liners have the potential to create a quicker drying sand scenario and I personally think it is only a matter of time before the industry needs to consider its current sand selection options.
Wash In Risk: I really cannot see the point of investing a not inconsiderable amount of money into lining a sand area when nothing is done to prevent water off a green, or thousands of square metres of ground above a bunker, running through it every time it rains. Excess water movement over sand will move it. No, you can't help or stop the immediate slope above, but a bunker should not have to cope with any more than what lands on it.
Consideration needs to be made to ensuring that surface water flows are diverted or collected by drain, gully or reshaping, or you are not really improving anything.
The last factor that is key is a lip ledge. I personally think any lined system 'must' cover a portion of the material at the outer edge, both for stability and, more importantly, to ensure that each trim does not extend the sand area beyond that protected.