Clay and Drainage

In the 18th Century a famous Engineer called James Brindley built the first modern canal in the UK. This was the Bridgewater Canal that was opened in 1761. He continued to build many canals and was followed by other famous canal builders such as Thomas Telford and William Jessop. In building these canals, all the Engineers had to consider one important factor, how to keep the water in the canal and stop it leaking out into the surrounding ground or countryside.

Surprisingly, this was very easily achieved by using a very common indigenous material called clay, a material that is found in plentiful quantities throughout the UK and the World.

Clay, when mixed carefully with water, forms a 'Clay Puddle' which can be moulded into lots of shapes and then forms an impervious barrier. A lot of the canals were lined with this material and, as it is evident, it is not often that we see many of these older canals leaking!

Clay, when mixed with water, can also be made into many items such as  Bricks, Tiles, Pots & Containers, Clay Pipes, Figurines etc.

When clay is found on a site, the depth of the clay layer can vary considerably from a few millimetres up to many metres. It is not unusual to find clay layers that are so deep that it is almost impossible to ascertain the full depth of the clay.

If your site has clay present in the ground strata then extra precautions have to taken in your drainage, as well as any structures.  The presence of clay in the ground strata is often evidenced by the fact that water will not drain away from the surface and that the topsoil layers are wet in winter and perhaps summer, or there are numerous ponds evident in your area.

When considering the installation of a new soakaway system in clay ground, we can see that water will not penetrate through the clay and therefore the water will be effectively contained in any trench, hole or soakaway constructed below ground.

Therefore, when clay is present on a site, septic tank systems will not be effective and rain water soakaways will not work . It is then necessary to look for other alternatives for the discharge of water from the site.

Furthermore, special precautions must also be taken when installing tanks of any type below ground, to avoid the possibility of uplift of these tanks when they are empty, as water is almost sure to be present in the hole excavated to install the tank.