Infiltration Rate of Soils

Typical values for the Infiltration Rate of Soils are given below;

The large range of values given above for the Infiltration Rate of Soils illustrates the need for field testing. The above Infiltration Rate of Soils values will be suitable for an initial or feasibility design, but detailed design must always take place based on site testing. The test procedure is outlined here.

The Infiltration Rate of Soils also tends to decrease over time. This is due to the voids within the soil becoming blocked by fines and sediment carried by the incoming water. To allow for this a factor of safety is included with the Infiltration Rate of Soils. This factor of safety should take into account the consequences of any failure of the soakaway and the size of the catchment area. Guidance on the magnitude of this factor of safety on the Infiltration rate of Soils is given below.

This can be reduced if a robust system of maintenance or pre-treating the incoming water can be guaranteed for the lifetime of the soakaway. Where regular maintenance is to be relied on, suitable access must be included in the soakaway detailed design to ensure that the Infiltration Rate of the Soil is appropriate to the conditions.

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