How much space for a sewage treatment plant?

[Kernow]

Hi,

We are currently in the process of buying a building plot (after a lot of searching). 

The plot measures approx 750sq metres, is there enough space on this to fit a sewage treatment plant and soakaways in?

 

On initial inspection I didn’t even consider that we wouldn’t have the space, until the solicitor sent a note to us suggesting we check that we have the space as we have no rights to drainage of neighbouring land. 

 

Am am I right in thinking treatment plants/soakaways should be 6m from a property and 3m from a boundary?

 

Thanks all

[ProDave]

Where are you (which country, different regs)

 

There are several aspects.

 

First off space to build the house.

 

Then you need about 2 square metres for the plant itself, BUT the big thing is there are building regs minimum distances from buildings, boundaries, roads, and watercourses.

 

Then there is thw question where it will discharge to?  A watercourse would be handy on a tight site.  Otherwise you are foing to have to create an infiltration field that can be quite large, and that too comes with building regs limits how close it can go to boundaries etc.

 

start by posting a site plan showing the proposed layout and we can work from there.

[Kernow]

Thanks,

The potential issue for me is the drainage field that’s required, the main part of the plot measures 30m x 17m with a smaller piece measuring 10m by 16m. 

 

Its going to be a 4 bed house in south west England. 

I have attached a plot plan so hopefully this helps. Our plot will be the area outlined. House location likely to be in the top right hand corner. 

 

Edited February 25, 2019 by Kernow

[ProDave]

Have you got a more detailed sketch of the plot showing where the house is likely to go?

[Jeremy Harris]

Do you know what the surrounding houses have in the way of foul drainage?

 

The older places most probably just have porous septic tanks, without proper land drains, as that was a pretty common way of doing things in that part of the world.  Our last house in Cornwall had an old (roughly 1920s/1930's) septic tank right in the corner of the garden, with lanes either side of it and no drainage field at all.  It was built the same way as a lot of them dating back a few decades, with missing bricks in the walls to allow effluent to seep out, not something that would be countenanced today, I suspect.  The same construction technique was used for the old septic tank at my mother's farm down there, too, with that tank being in the middle of the yard, surrounded by farm buildings and the house itself and no drains leading out to any of the fields.

 

A treatment plant does offer a bit more flexibility in terms of how to dispose of the effluent, and the general guidance on the distance from boundaries, roads etc can be flexible if the plot is restricted, I found.  For example, our treatment plant is only about 2m from the road, and was allowed because there was nowhere else we could site it.

 

There are options to use soakaways or drainage mounds with a treatment plant, but there will almost certainly be a requirement to get approval from the Environment Agency, whatever you choose to do.  They were helpful when I obtained a permit to discharge, but that may be just that I happened to deal with a helpful individual.

[Kernow]

2 hours ago, ProDave said:

Have you got a more detailed sketch of the plot showing where the house is likely to go?

 

There is no detailed planning yet so we can put the house where we like, within reason. 

 

Its the potential size size of the drainage field that is the issue, the neighbouring properties will be on private drainage as there is no mains sewarge in the vicinity. 

[PeterW]

Don’t forget that both your treatment plant and your rainwater will both need soakaways. These are sized from the percolation test, that’s your starting point.

 

If you have good permeable soil then you can have a much smaller soak away and drainage field - think how the pair will work on the plot. 

 

Another option is the drainage cubes but I’m not sure if they have been certified for leach field use. 

[Jeremy Harris]

2 minutes ago, PeterW said:

Another option is the drainage cubes but I’m not sure if they have been certified for leach field use. 

 

It's a very grey area, as Part H is pretty vague when it comes to the requirements for treatment plant soakaways, and the EA aren't a great deal of help either, in my experience.  In theory there's no good technical reason why the effluent from a treatment plant shouldn't be treated in the same way as grey water, as there's no requirement for tertiary treatment.

 

I found that it really comes down to the flexibility of the EA and building control in the particular circumstances.  In our case BC were very understanding, and although Part H says that a treatment plant must not be within 10m of a watercourse, our BI said that it was silly to enforce this when the EA had given us a permit to discharge to the same watercourse.

[ProDave]

Even with a treatment plant, you are supposed to have separate soakaways for rainwater and waste water.

 

Have you actually explored the possibility of getting permission for a soakaway under one of the adjoining parcels of land?

 

The very first thing you need to do is get a percolation test done.  from this you can work out the area of soakaway you will need.  Then you can draw that onto the plot (allowing clearance distances to the plot boundary) and see how much it takes up, and how much land is left for the house.

 

Does it have to be 4 bedrooms?  3 bedrooms and a "study" would reduce the area of land you need (lower assumed occupancy)

[Kernow]

Thanks all for taking the time to reply,

I’m already aware that we will need separate soakaways for the treatment plant and rainwater and planning to use crates for the rain water soakaways. 

 

We need a 4 bed house due to our family size, but planing on 2 stories to minimise the footprint. 

 

Best get sketching out a few layouts to get an idea of what will fit where. The soil conditions should be fairly good (whilst we haven’t done a percolation test), I know it’s not clay and is a gently sloping site in our favour. 

 

We we haven’t explored the option of having a soakaways on neighbouring land, but this is something we can look into. 

 

Thanks

[Roger440]

As Dave said, perculation test as a matter of priority, ie, BEFORE you buy it. If you cant install the required soakaways, you cant build!

[Kernow]

Thanks for the advice everyone, I have done a bit of asking around and research with local contractors. The typical drainage field size for properties around is between 40-50sq m, and all of the neighbouring houses are using septic tanks and soakaways without issue. 

 

Even if if we had to have a drainage field size of 150sq m we could easily fit it in so plenty of space. 

 

Thanks