# Existing Arenas: Solving the Problems

## Does the sand gradation maintain "critical tension"?

If you have problems with your existing arena, they are usually to do with drainage. To fix the problem, we often recommend capping your existing manege with a layer of finer sand to change the drainage mechanism. This finer sand layer will have a higher 'critical tension', retaining a certain amount of water within it. It is this water retention that will keep the surface firm. Although it will hold water, it will not 'clog' -- any excess water is simply transmitted through the sand and drained away.

The finer sand layer has to be designed as a distinct layer which will resist being mixed into the existing sand beneath, to maintain optimum performance. However, as some mechanical mixing is inevitable during the use of the sand school, the chosen sand should also, even when well blended with the existing sand, produce a mixture with a substantially higher critical tension than at present, while maintaining drainage and avoiding clogging.

To illustrate, this experiment should demonstrate how a layer of fine sand will affect the critical tension, and thus the water holding property, of your sand school.

• Cut the bottom off a clear plastic bottle. We suggest a 2 litre plastic drinks bottle to achieve a sufficient depth.
• Remove the cap from the bottle, and replace it with a piece of muslin or nylon mesh, held in place with string or an elastic band.
• Ready a large jam jar, big enough to set the bottle in, cap downwards.

## Performing the experiment:

1. Completely submerge the bottle in a bucket of water, with the cap downwards.
2. With the bottle still underwater, pour sand from the existing manège into the bottle, through the water, until the bottle is half full. This ensures that all spaces in the sand are filled with water.
3. Lift the sand-filled bottle out of the bucket, and set it in the jam jar.
4. Allow the bottle to drain into the jam jar until it stops dripping. This may take some time.
5. You should be able to see whether the sand column is still holding water, by its darker colour. The water will be held at the top of the column of sand -- it will have drained from the bottom up. Measure the height of the saturated sand layer, if present. This is the critical tension of the existing manège sand.

## Does the arena ride too deep?

The problem here may be that even though the sand grading is correct the arena has not had sufficient water.  We used to recommend that riding arenas were initially soaked with water in order to achieve stability.  However, now we recommend that you wait until the arena has had sufficient rainfall.

Be Patient!  Wait until you have had at least 2 inches of rainfall.

A good way to measure the rainfall is to nail a can to a post.  Put a glass jar in the can and use as a rain gauge to determine when 2 inches of precipitation has been retained.

The next step is to contact us, and discuss your problems with us. Knowing the critical tension of your existing arena sand enables us to recommend and source the right kind of capping sand to use in order to solve your problems.