A trencher will dig a trench in the soil and lay the pipes as well. In some cases, this machinery is additionally able to backfill the trenches with gravel. Sometimes a trencher will be preferable to the trenchless plough. For example, in an area with (boulder) clay in the soil. If this boulder clay occurs at different depths, the pipes will sometimes lie in the boulder clay and in other places on top of it. Depending on the structure of the boulder clay, drainage is sometimes possible in this kind of clay. In these cases, the trencher is the better method for laying as the trench will be filled up with well mixed material. The permeability of this material is usually quite good and plays an important role in the drainage of water. Even when drainage is needed in weakly structured soil, the trencher is preferable. By exposing the dug-up material to the open air for a number of days, it will dry out slightly as will the trench itself. The permeability of the trench and the consistency of the material that will be used in backfilling, will be improved greatly by this. The weather will obviously play an important role. It is also possible to use the trencher when plots of land are being levelled and little or no trouble is expected from the settling of the trench. This might be the case for instance when the drainage is installed in the direction of cultivation of the plots of land and on light clay soil or sandy soil. Hardly any problems will be experienced if the land is being used for crop farming or corn cultivation.
The filling of the trench
To increase the draining of the trench it can be partially or completely filled. Different kinds of materials can be used, such as gravel or gravel mixtures, shells, glass slag, glass beads or drain sand. The draining capacity will increase by using these materials. Because of the high delivery costs this method is, from an economical point of view, only attractive if the supplier is within a reasonable distance.
A potential disadvantage is that the trencher might leave ‘scars’ in the grassland.