It's hard to believe that May is over. It's amazing what three weeks can do! The temperature finally picked up and with it Mother Nature woke up. The course healed exceptionally well from aeration and the new cultural practices were very successful. The roots on the bad greens have not been this healthy in a long time so it sets the course up well for the summer. The course has been playing hard and fast for the most part as the region is in marginal drought conditions; it is a lot easier to add water than take it away!
Over the last week the weeds have finally been sprayed so should be disappearing soon. We have also been spot killing poa on the greens which can be identified by the blue/black dots that are turning brown. As last year, Annual Bluegrass Weevils are attacking the poa also on collars so Mother Nature is giving a helping hand with natural poa control. We will let them munch away for a bit longer and them kill them off before they run out of food and possibly take a liking to bentgrass!
ABW munching on the poa on 12 collar
Poa spotted with herbicide on 4
As promised I wanted this post to discuss the bunker project.
It is hard to think of a bunker as a hazard when you consider how much work is needed to maintain them. Bunker types vary a lot from the ruggedness of a Pine Valley, the steep stacked sod walls of a Links course to the perfectly manicured sand of Augusta National. There really is no set design just one that fits the environment and overall feel of the course itself. LedgeRock's design called for large bunkers with some flashing and grass faces with a more manicured look. It fits well on the property but unfortunately flashed sand results in washouts. Washouts not only are labor intensive to have fixed after a storm but also result in silt and rocks contaminating the sand.
So why do bunkers wash out? The sand sits on a soil base. When it rains the water runs through the sand and along the surface of the soil - hopefully to a drain. With excessive rain the sand fills up with water; when this occurs the sand takes on the characteristics of a liquid and flows like water down the slope creating the washout. The angle of repose of the sand is also important as the closer to this angle the face is, the more prone it is to washing out. The angle of repose is simply the angle that the sand naturally supports itself. When you look at a pile of sand, the cone it forms is the angle of repose. If the slope in the bunker exceeds that angle the sand cannot hold. So to prevent washouts the slope has to less than the angle of repose and the water has to be separated from the sand by a drainage layer.
When construction started the only option for lining bunkers was fabric. While they work short term the decision was made not to go to the extra expense for a short term gain and see what solutions would come in the future. After a year or so of opening the club installed liners in a few of the worst bunkers to help play-ability. Inevitability after a few years the issues with the fabric arised and while the sand is still relatively clean in them, the staples have come out and it is lifting. The fabric has also matted down so no longer prevents washouts like it did when it was new.
Fabric liners installed in 2007 by 18 green
On the driving range a sod based liner was also trialed to see how it would work. The idea is that the thatch of the sod acts as a barrier to stones coming up and aides in separating the sand and soil. Our test showed that it worked well as a barrier but it did not hold up well under washout conditions which are required for flashed faces.
In the mid 2000s an Australian product called Sportcrete was launched in the US. It was a stone base that was sprayed with a binding agent and it seemed like a good solution. Unfortunately the product did not hold up and ultimately disappeared from the market.
With the short term success of the fabric liner and the sod, the board asked me to investigate a more permanent solution for the bunkers. At this time some more porous liners had made it to market.
The Better Billy Bunker method (BBB) was derived from a system that was invented at Augusta National where a stone drainage bed was covered with fabric. While this worked well it still involved a liner so the BBB method replaced the fabric with a spray to lock the stone bed together.
A superintendent in Sweden created a porous concrete mix called Capillary Concrete which also works by creating a porous later between the sand and the soil.
The next liner Bunker Matrix was created locally by Dan Meersman at Philadelphia Cricket Club. Dan specced a porous asphalt to be used as the layer and has had great success with it.
As I researched these products, I was leaning towards the BBB method but stumbled over a UK product called Blinder Bunker. Blinder used recycled crumb rubber and intrigued me as not only is it porous, but flexible also - which was my biggest concern with the other methods.
I contacted them and they sent me a sample. As soon as it arrived I knew it was the solution LedgeRock was looking for but the only issue was how to get it here. So after a lot of back and forth I became the US licensee for it and went to London last fall to learn how to install it. They have installed Blinder at more than 100 clubs all over the UK and Europe since 2008 and over the last month the first Blinder Bunkers in the US were installed in three bunkers at LedgeRock.
Blinder bunkers at Wimbledon Park Golf Club (with Center Court in the background)
Burhill Golf Club in Surrey where I learned to install Blinder
So how do you rebuild a bunker? The old sand is removed and, for Blinder, the old lip is removed also to create a shelf so the product can be locked in. This prevents water or other contamination getting under the liner and also ensures that there is liner available if the bunker is edged back in time.
Removing the sand on 15
Removing the old lip on 13
Details of the shelf on 15
Once the shelf is built, the base of the bunker is shaped to make sure it falls correctly and that the slopes are within the angle of repose.
Final shaping on 15
Checking the slope to make sure it is less than the angle of repose of the sand
The drainage is then added. While the porous liners are essentially a drainage layer the water needs to exit the trap. The minimum requirement is a drain that runs along the floor but since drainage is cheap and the floor is being covered it makes sense to add extra drainage to make sure the water can get out even faster.
Once the drainage is installed Blinder requires a layer of modified stone to give the rubber a consistent solid base and one that the water can run on to the drains.
The Blinder is then installed. It is recommended that it is left for 48 hours to ensure that it fully sets.
Once Blinder sets it is flexible enough to be picked up like a rug!
Then the lip gets rebuilt. Based on what I saw in the UK, I decided to use their method of stacking sod and the results look great. Originally the bunker lips were built with sandbags that eroded away when the turf stabilized them. The stacked sod also reduces the risk of contamination from stones or silt from the lip area.
Once the lip is finished the sand is added, packed and watered. It usually takes a few weeks for the sand to fully settle. All the liners are designed so that the sand bridges the material so the liner does not get clogged with sand particles.
Now that these three bunkers are completed the GAP committee plan to work on creating a list of priority bunkers so that the club can continue to replace bunkers going forward.
As always if you have any questions on this or anything, email me alan@ledgerockgolf.com
