Testing the ground for its suitability

Testing the ground for its suitability for soakaways in accordance with BRE Digest 365 involves excavating a trial pit of sufficient size to represent a section of the design soakaway, filling the pit three times and monitoring the rate of seepage to represent soil moisture conditions when the soakaway becomes operative.

The trial pit should be excavated to the same depth of the anticipated soakaway below the invert of the drain. Ideally the pit would measure around 0.45m wide x 1.5m long and 3.0m deep to allow our 2500 litre tank to have sufficient water to bring the level up to about 1.0m below ground level. The pits sides should be as near to vertical as possible for accurate volume measurement, and if necessary in unstable ground, be filled with a granular material such as 10mm pea shingle. If conditions allow, the pit should be filled and drained three times with particular attention taken to the time in which the water level dropped to 75% and 25% full.

2500 litre towable bowsers

Where shallow soils are impermeable and conventional soakaways are not realistic, soakage needs to take place at greater depths. A deep borehole is drilled to find permeable soils and the borehole installed with a plastic liner. The testing of this is a borehole soakaway which we can carry out from one of our 2500 litre towable bowsers.


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