Infiltration trench

By Antje Backhaus, Ole Fryd and Marina B. Jensen.

An infiltration trench is a soakaway with trench geometry, e.g. ½ m wide, 1 m deep and several metres long. Making the storage volume narrow and elongated achieves a large wall area and hence a shorter emptying time compared with a more cubic shape (see closed stormwater basin). An infiltration trench can be constructed in an E shape, with 2-3 m between the arms. It is not possible to expect infiltration to take place through the bottom – this will slime up over time. The soakaway elements are often packed into a geotextile, which can be an advantage during the construction phase and if the soil is loose. If the soil has a good structure, the soakaway can function without geotextile.

Figure 1: Infiltration trench with soakaway units

Figure 2: Diagram of an infiltration trench with stone