How close to a soakaway can I get?

[AndySat]

Apologies in advance for a newbie question....

 

I'm looking to build a detached garage (part of a bigger house build project, but that's another story) at the side of the plot nearest the road. So far, so good, but there's a manhole cover towards the edge of the plot, close to where the back wall of the garage will be. It's an inspection chamber for the neighbour's foul drain soakaway. Of course, it's not on anyone's plans and he knows nothing about it.

Leaving aside the question of whether it should be there or not, how close to it can the garage foundations be? It's likely about 15 years old, so probably just a big hole filled with stone rather than plastic crates and it seems from the slight depression in the ground to lead in the opposite direction to where I want to build. We had an engineer on site for the soil stability tests for the house and he didn't seem too bothered about it, but I'd like to understand whether it's a potential show-stopper, or something I can work around with e.g. deeper foundations and lots of concrete!

 

Thanks!

[ProDave]

Does the garage need a building warrant, that will be a deciding factor.

 

If installing a soakaway now I think it has to be 5 metres from a building (check the latest version of building standards)

 

Lift the inspection cover and see which way it flows?  Send a drain rod down and see how far it goes before it hits any obstruction (the actual soakaway)

[saveasteading]

Are you saying the manhole or soakaway is the issue?

Have you lifted the cover? 

I'd expect to find a pipe in and out.

If you push a drain rod along, you should find the soakaway distance. Probably where you guess.

 

It's worth getting a pair of lifting keys as you will be doing this often.

 

If it is a rainwater soakaway then the 5m rule applies,  as it is the movement of water in the ground that is the concern If it is a manhole it doesn't.

 

Sounds sortable. More detail please.

What's in there? Distance?

 

 

BUT you say foul soakaway. That would be illegal and so a very nasty thing to have on your land.

 

 

 

[AndySat]

Thanks both. My neighbour found some paperwork that confirms that it is the soakaway for their septic tank. The plot was part of a field when his house was built, so this was probably the easiest option back then.

I lifted the cover and found two pipes as expected, one heading in the direction of the neighbour's house and one leading onwards somewhere. Paperwork shows the soakaway is a porous pipe in a gravel bed but doesn't say how long or where it goes - I assume in a straight line away from the inspection chamber. I'll see if I can get a rod in there tomorrow and find out more.

I'm not too concerned about the manhole itself, but it's going to be tricky moving the garage 5m away from the soakaway and still meet the planning requirement for parking and turning space...

[saveasteading]

4 hours ago, AndySat said:

tricky moving the garage 5m away from the soakaway

That isn't really a soakaway that would require 5m as the water will drain slowly into the ground and can't wash it away.

The amount of water is small and it is spread over the length of the pipe.

 

If I was your Engineer then I would be able to write a letter to satisfy the bco. (subject to knowing  and being happy with all the details).

Plus, if necessary, you could  change the perforated pipe to solid and it is just another drain.

 

Even for a rainwater soakaway pit I got leeway for 4m once, but that depends on the ground.

[ProDave]

So you have your neighbours soakaway in you plot?  Where is YOUR soakaway going?

[AndySat]

7 hours ago, ProDave said:

So you have your neighbours soakaway in you plot?  Where is YOUR soakaway going?

Well, in the time-honoured tradition, my soakaway is going in the field next door, which we own.

 

Looked again at the papers provided by my neighbour and his assessed soakaway required is 93m2, which apparently corresponds to a trench 155m long! I'm not sure what the engineers would typically do in this case - dig a long trench or loop it back a few times?

 

I managed to get 10m of drain rods into the pipe leading away from the inspection chamber without any resistance, so I'm hoping that it's a long linear soakaway and not some kind of herringbone design. But it looks like I'll need to get a sonde and/or camera in there to see where it goes...

[ProDave]

Try dowsing rods and have a walk around