Geotextiles: The Arguments For and Against
One of the most frequently misunderstood aspects of arena design is the use of geotextiles, and their alternatives. We have provided this article especially to help you to decide which is best for you.
Drainage is one of the most important aspects of arena design. To maintain drainage, the layers in an arena must be kept separate. If layers in an arena mix, drainage may become blocked as particles from overlying layers melt into underlying layers, and as particles from underlying layers float into overlying layers. This 'melt and float' can be prevented by ensuring that each layer in the arena, although coarser than the one above, is sufficiently fine to prevent finer material being washed down through the spaces between the grains. This is called a graded filter, and will be discussed in the next article. Another method is to place a Geotextile in between layers.
There are certain disadvantages to Geotextiles. They are susceptible to blockage by sediments; organic residues; plant roots; fungi and algae; viscous petrochemical compounds and slimes. In the context of riding arenas, consideration should also be given to the effect on a geotextile of the breakdown of organic riding surfaces (such as shredded timber or bark) and to a lesser extent on the breakdown of horse and pony droppings to form an impervious bio-detritus coating. If, on inspection, the geotextile is seen to have been blocked by detritus, it must be replaced to re-establish the drainage regime.
Rips and Repairs
Geotextiles are susceptible to being ripped if the overlying layer is too shallow or gets displaced during exercise. If horses or ponies - especially young stallions - are left unsupervised to exercise in an arena which is also required to double as a holding area, then their inquisitiveness frequently leads them to attempt to dig up the geotextile. Consequently, a graded filter design is the preferred option in such circumstances. Once ripped the Geotextile has a tendency to admit the overlying layer through the rip, causing it to ride up through the layer and expose itself to further damage. The upper layer simultaneously pipes into the underlying layer blocking off the drainage path. We recommend that the geotextile be overlapped and at least glued with silicone sealant where applicable to guard against this problem at the joins (The manufacturer of Terram recommends that the fabric should be stitched together at the joins when used in equine arenas). Overlap the topmost layer in the direction of drainage flow. Should a rip occur it should be repaired immediately by clearing the sand off the affected area and glueing down a patch (min. size 1.2m x 1.2m) over the rip. The sand should then be replaced.
All that said, Geotextiles are generally cost effective to buy and to lay. They form a visible barrier between different media, admitting only moisture across the barrier, provided they are properly selected for performance and protected during use. In certain areas of the country, where the materials for a graded filter cannot be sourced nearby, they may provide the best solution.
Terram Fabric Grade 700 is available from us ex stock in 100m x 4.5m rolls or in cut lengths.
Disclaimer: The foregoing is a design guide only, material properties can vary. Site conditions can impact substantially on a design. Professional advice is recommended
Next Article - Graded Filters: From Surface to Subgrade