Question ref soak pit

Is the soakaway proposed/conditioned as part of your planning permission?

The soakaway needs to be constructed in accordance with BRE 365 and needs to be min. 5 metres from any structure and min. 3 metres from any boundary.

A soil infiltration test needs to be carried out. The results of same will determine the final size of the soakaway. Normally engineer looks at results and then specifies the final size of the soakaway. At least that's the way it works for me!

As to when this is done depends on your planning permission. Have a look at/read the conditions. Some local authorities now require the soil infiltration test/final soakaway design/sizing to be carried out prior to commencement (and detail confirmed to them). Other local authorities do not, so normally contractor (while on site) can do soil infiltration test (to engineers instruction) and final size of the soakaway confirmed (on site).

As mentioned, I would often specify the builder carries out the test (in accordance with BRE 365 and generally to engineers instruction) and builder reports results back to the engineer (for final design/sizing of soakaway).

If you google, there are companies out there who will carry out the test.

No idea of your location, but in most of the Dublin LAs, for planning, if you do not propose a surface water soak away, or other means to deal with surface water drainage within the site, it will either be requested that you show them/propose to them how you will deal it, either by means of a request for additional information or submission for approval prior to commencement.

@Tim Robbins if you have not proposed a surface water soak away as part of your planning application, read through your planning permission conditions and see if it says anything with regard to a surface water soak away and/or surface water drainage.

Applies to newer parts of Dublin too, where there are storm drains/separate surface water drainage systems. They are overloaded with surface water so policy is with any new development to attenuate as much as possible within sites.

And that too!

The storm drains/separate surface water drainage systems in the past discharge to rivers/watercourses so increased run off from new developments just means more water and potentially more flooding somewhere down the line.

A soakaway is not over engineering. Really quite simple/straightforward technology if you have the garden/site to accommodate it. If you or your engineer do not want a soakaway, you or your engineer are going to have to come up with and propose alternative means of attenuating surface water run off (like starting to look at green roofs, water butts, water storage, etc.). If you have engaged an engineer, they really should be advising how to comply.