Soakage testing or percolation testing is required on sites where it is intended to use a soakaway.
The test determines the rate at which the ground absorbs a known volume of water. It ensures that the ground is suitable for a soakaway and that the soakaway is designed properly.
Typically, soakaways are used to collect surface runoff prior to being discharged into the surrounding soil. They are usually employed in areas where the surface run-off cannot be disposed into existing sewers or watercourses.
A soakaway is constructed in one of two basic forms. A conventional soakaway comprises a partially perforated cylindrical chamber, which allows the drainage of water into the surrounding soil.
In cases where impermeable soils overlie the permeable strata, the soakage must take place at depth and so a deep bored liner is used. This is known as a borehole soakaway. Here the water is transported from a sealed storage chamber to the soakage medium by a small diameter plastic or steel pipe, again perforated in part.
There are a number of permeability tests for measuring the rate of flow and determining whether soakaways may work effectively at a site. These range from small to large scale. Small-scale soakage tests are only applicable to draining relatively small areas. We have our own plant and equipment and can offer the following soakage testing methods:
- NHBC: Chapter 5.3; Percolation Test for Surface Water Soakaways (Small-scale)
- BS 6297: 2007; Percolation Test for Septic Tank Insulations (Small-scale)
- BS 5930: 1999; Falling Head Test in Boreholes (Small-scale)
- BRE Digest 365: 1991; Falling Head Test in Trial Pits (Large-scale)
- BS 5930; 1999; Constant Head Test in Boreholes (Large-scale)
We have considerable experience in undertaking site investigation soakage testing, both for conventional soakaway design, as well as the drilling, testing and installation for borehole soakaways.