Drainage is also a major arena construction component that is very often overlooked or deemed unnecessary in our dry climate.
Most arenas are constructed on a hard compacted base which is given a cross fall to allow water to move across the arena and off to the side or to a predetermined corner with some form of grid for storm water control. This is effective on a hard compacted surface where the water can move freely, once sand or surface is added you slow this lateral movement down considerably, especially of the rain soft and consistent. Hard rain in short bursts tend to move off the surface quicker.
If your arena is for private use and you don’t mind a few days when you can’t ride then this system is adequate, however your surface will be waterlogged and therefore will not perform as it should. The addition of subsurface drains will assist in the draining process but will only work in small strips in close proximity to the actual drain. The sub surface drains must be open to the surface and not covered with base material or they will not assist with surface water at all.
Your surface must also be of such quality that the water can freely move through it or the water will still sit on top and not reach the drains. An All Weather drainage blanket is the only way to ensure that every part of the arena drains at the same rate thereby ensuring consistent footing in all parts of the arena all the time. This is generally constructed with a 100 -150mm layer of clean stone over a network of perforated pipes which allows for vertical movement of water through the surface. With this system it is possible to harvest water from your arena and recycle it as well as store water in the basin created by your drainage system which then can be used to put back on to the surface.