Building the Best Putting green using the USGA method – Part 3Go back to Building the Best Putting green – Part 1 – How does it work? The next step is to make sure any machine tracks in the bottom are removed and rake a nice even surface again. Install stakes at regular intervals over the bottom and mark them for the layer thicknesses to come, which are: 4” above the bottom set a mark for the top of the gravel line, 2” above that another line for the chocker layer and 14” above that another line for the rootzone mix which is also the final elevation of the green. You will use these lines to make sure each level conforms to the subgrade, and the contours of the finished product will be as planned. Now you can start to install the 4” gravel layer. Remember, don’t contaminate the gravel, the product you are using, if it matches USGA recommendations, will probably be washed to remove any fine material. In the past pea stone or river stone was often used, but today we are much more often using granular material. The advantage of the granular material is that stays in place much better while you are adding the consecutive layers. The pea gravel is round so it won’t compact, and makes it more difficult to add other layers without disturbing the bottom 4 inches. The gravel is in, what now? Now we have to install the intermediary or choker layer. This layer is designed to make sure none of your very expensive rootzone material seeps into the gravel layer. If you read the USGA recommendations carefully, you can build without this layer as long as you stick to more stringent specifications for the gravel and rootzone layer. On the other hand, putting a choker layer in anyhow won’t reduce the effectiveness of the green, so I would put it in as an added security; after all you are using this method to build the best putting green possible. Before you do this, if you really want to get that flowerpot theory working for you, you can install a vapour barrier along the perimeter of the green. That would be the same as the 6mil plastic used in home construction. What it does is prevent the surrounding soils from sucking the moisture out of the green, or in some cases from adding water through a high water table. Now you can add the sand, this is one of the hardest parts as it is a very thin layer at 2”. One method I used to use in construction is to take a two 2” pipes, fill in between with sand and use a straight board to skim the excess off. Make sure you compact this layer properly, driving light equipment or using a roller will work well. Again, as with every step to get the best putting green, try to avoid contamination from native soil. It starts to look more like a green, what next? Now we can finally install the rootzone material. The keys here are like before, avoid contamination, and avoid having the layer below shift while you bring in this layer. It is the consistency of the layers in the green that make this style of green successful. It is a good idea to build up in layers of approximately 4 inches and making sure it is properly compacted before continuing on to the next layer. One trick I have seen in the past, that will make the best putting green even better, is to add an electrical wire around the perimeter at the bottom of the rootzone, then bringing it to an irrigation valve box. After many years, you will find the edges of the green actually shift. If you put a wire tracer on this wire, you will be able to restore the original shape and size of the green at any time in the future. Once the green is filled in and compacted, make sure the excess sand is raked out over the rough and the outside grade blends in perfectly. I would recommend putting construction flags or other methods of identifying the edge of the green for seeding and/or sodding. If the steps are properly done, the green will blend in so well to the surroundings, that the flags are the only indications of the edge of the green. Now I would lay a strip of rough sod along the rim of the green to identify the edge. Can we put grass on the green yet? Yes, this is the next step. My recommendation for the best putting green result would be to seed. The reason I don’t like to sod is it takes a long time to get the surface smooth enough for a nice true putt. Also, you have spent so much effort and money on the rootzone, you don’t want to contaminate it with another root material, which means your only sod option would be washed sod. The drawback to seed is it takes a long time to mature and takes probably more TLC in the beginning, but you have a better putting surface with less problems in the long run. In order to seed, or to sod if that is your wish, you can follow the directions in traditional style of green. Now you have the best putting green science can build, happy putting! Any questions? Contact us!
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