A soakaway is a system to discharge water into the ground. Virtually all new developments have a soakaway system, and in the past not much thought was given to the design of these.
An Architect would often specify “1m3 hole filled with broken rubble to Building Control officer’s agreement”, or it would just be left to a contractor or builder who would “fill a hole with whatever broken rubble they needed to get rid of, similar to the last job”. The flood water management act says that any soakaway shared by more than one household needs to be designed and constructed to adoptable standards.
Apart from the legal requirements, you naturally want a design which is appropriate – Is a builder really qualified to undertake an engineering design? Some soakaways even correctly designed do flood, but the decision about when should be an informed one, not a guess.
Designing the soakaway
The design of a soakaway can be complex, however, it all depends on many factors:
- Groundwater level
- Type of ground
- Permeability of ground
- Space available
Carrying out a percolation test is critical, this allows us to understand the performance of the ground in question. Once this has been carried out and the results produced, we would be able to start the design process.
We use specialist soakaway design software which we input the percolation test results to obtain the soakaway sizes according to BRE365. However, it is not always cost effective for smaller soakaways so we can design these based on our experience.