Surface and foul water plans

[Sjk]

Not sure if this is the best place or if it is better in the design section?

 

One of my planning conditions is 

 

Prior to the commencement of development, detailed proposals for the disposal of foul and surface water shall be submitted to and approved in writing by the Local Planning Authority. The submitted details must include a diagram of the surface water system, including details of the hydrobrake system used.

 

I am allowed to use a the foul sewer (darker green lines) for excess surface water (blue lines), but have to use a hydrobrake to limit it to the agreed amount. 

 

I've been trying to come up with the plans needed to satisfy the condition, I'm a little concerned there is a 3 foul sewer pipes (lighter green lines) under the house especially considering it will have a slab foundation. 

 

It all looks rather messy, the land slopes to the front of the house.

 

Any help would be greatly appreciated 

 

 

Edited February 17, 2020 by Sjk

[PeterW]

@Sjk do you have that picture minus it’s lines ..? Just put dots on where the soil stacks are  

 

And have they specified an attenuation tank or hydrobrake..?

[Sjk]

Thanks Peter.

 

There has only every been mention of a hydrobrake.

 

Edited February 17, 2020 by Sjk

[CC45]

We had a verbal quote for a hydrobrake - far more expensive than I thought, it was several thousands.  We dug down deeper and got drainage for a soakaway.  Tricky for you - very little (if any) room for a soakaway.

[PeterW]

@Sjk I’ve been looking at this and I’m missing a bit of information ..! What limit have the sewerage company put on your outlet, and what’s the total roof area ..?

[Mr Punter]

It looks like one of your runs starts outside your plot boundary.  Also you may need to be careful with scaffold and eaves overhang with the neighbours. Roof area looks about 50m2

[Sjk]

Ah sorry, they agreed to allow a max of 0.1 l/s , which should be all that is needed for a once in 100yrs +CC situation. I didnt realise they were several thousands, that would be a swift kick as the rates are so small. The roof is around 53sqm.

 

I thought a soakaway had to be X number of meters away from a building, and X was greater than what we have to play with. Could be wrong though.

 

The land to the north is own by the LA, who have been very helpful. 

Edited April 22, 2019 by Sjk

[PeterW]

Are you sure it’s 0.1l/s as that seems low..? Hampshire has a 0.072l/s/m2 rain rate at T500, and 0.018 for the T1 range which is just less than 1l/s for normal peak rainfall. This would mean you need an attenuation tank of about 2000 litres before the hydro brake. That doesn’t seem right ..?

[CC45]

ours was designed to discharge at 1l/sec so 0.1 does look low - it will need a lot of storage 'upstream'.

[Sjk]

"peak rate of 0.1 l/s surface water run off to public foul sewer can be allowed"

 

2000l tank? The archaeologists will love that...

 

Also, the only logical place it could go is under the drive, not sure how it will fair with a heavy car on it.

 

I'm hopeful we can get the limit increased, as it is so small. If it was upped to 1l/s, I assume the tank would be a lot smaller?

 

[Ferdinand]

1 minute ago, Sjk said:

"peak rate of 0.1 l/s surface water run off to public foul sewer can be allowed"

 

2000l tank? The archaeologists will love that...

 

Also, the only logical place it could go is under the drive, not sure how it will fair with a heavy car on it.

 

I'm hopeful we can get the limit increased, as it is so small. If it was upped to 1l/s, I assume the tank would be a lot smaller?

 

 

Jeremy for one has one of these under his drive made from IBCs.

 

Ferdinand

[Jeremy Harris]

4 minutes ago, Ferdinand said:

 

Jeremy for one has one of these under his drive made from IBCs.

 

Ferdinand

 

 

Yes, we have a couple of thousand litres of surge storage under the drive, but it's not IBCs, I used 20 off heavy duty Aquacell crates, the blue ones that are OK for up to 44 tonne vehicles: http://aquacell.wavin.co.uk/

[CC45]

Our chap also talked about increasing the size of all the pipework that fed to it - in effect creating some storage in the pipework.  Not too sure how much that would add.

 

I'd try and get a soakaway to work if possible but it will have to be certain distances from boundaries (2.5m?) or buildings (5m?).  What's the water table like?

[Sjk]

Cheers chaps, I'll have a think about this one.