All new developments require a surface water solution. This is often dealt with through on-site soakaways.

Usually if this is deemed possible and once a site has obtained planning permission, a specific condition is often included by the local authority, which requires the potential performance of soil soakaways to be ascertained from soil percolation testing and to provide soakaway design parameters.

There are a number of publications and method guidelines which outline the procedures for such tests, namely:

• BRE Digest 365: 1991 Soakaway Design

• 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)

It is essential that the type of test acceptable to the regulatory authority should be confirmed prior to commencing the site work. It must be emphasized that some of these standard test procedures are costly and time consuming.

Consequently, TSL have developed a bespoke pragmatic approach, generally in accordance with the methods above, which is more cost effective and increasingly is being accepted by local authority and NHBC building control. As an alternative, in situ permeability tests are performed in boreholes.