Installing treatment plant/drainage field before house construction?

[flanagaj]

We currently have granted PP and are currently waiting on a revised application.  The house will be sited in the same location though.  I was wondering whether I could install the TP and drainage field before any other development works starts.  Given a drainage field has to be in the top 750-900mm of soil? This along with distance from TP and TP distance from house, means that the soil pipe trench depth at the house is all calculated relative to the distance to the drainage field and the required fall.

 

I suspect that to install the drainage field, I would have to get the conditions signed off on the current application first, before I could start?

 

If we have to go to appeal on the current app, then it won't be decided this year and as I get a decent amount of annual leave, I wanted to try and get some tasks done.  I've also got a retaining wall that needs to go in.   All depends on what constitutes commencement of development?

 

Edited January 31 by flanagaj

[Jilly]

It depends if it’s a Building Control matter or a pre-commencement condition. You could start on a Building Notice on the first pp, but would presumably go for full plans on the amended application. Maybe speak to BC, they can be quite helpful?

 

 

[crooksey]

As long as your proven percolation tests come back correctly, take photos and it will be fine.

 

Only thing is, you will need to know the depth of the TP relative to the fall of the rest of the drainage runs.

 

If you really wanted to get it in, sit the tank a bit deeper, get a pumped outlet and then put the drainage field in nice and high.

 

Such a small job in the scheme of things, and hiring a 5t digger seems a bit of a waste when you probably have a bigger machine in when you start the build.

[saveasteading]

On 31/01/2025 at 18:35, flanagaj said:

I was wondering whether I could install the TP and drainage field

Whether you could is dealt with above.

Whether you should?

It is taking a risk regarding approvals and any changes during construction.

It will be a 2m to3m deep hole so it's maybe better to wait, and a bigger digger can hoist in the tank and hold it safely while you shovel gravel around.

PLUS it might be in the way, if you are tight for working space, and damaging it would be awful. 
That goes for the pipes too, as you will surely be driving machines around the building.

[Alan Ambrose]

I assume your LPA doesn’t have CIL? That would argue a ‘no’. If they don’t, then at least one other here (sorry, can’t remember who) has started a build then proceeded to a different design when it got PP.