Soakaway positioning - Soakaways under carparks

[flood]

I am in dispute with a builder who has put the soakaway for a building's foul water system under the carpark which is currenty stone finished but will eventually be tarmac. The soakaway floods. The builder says it would have been ok if we had tarmac from the start. Is there any 'official' infomation on where soakaways should/can be positioned.Is putting soakaways under carparks, tarmaced or not, a good idea.

[flowjoe]

A soak-away should be at least 5mtrs from the property, it doesn’t matter what its under as long as it soaks away!

A soak-away that floods doesn’t sound promising at all.

[ABILITY]

Flowjoe.

See you are in the North West like us.
Would be useful to get your contact and services details if possible - by private message?
We often encounter drain / sewer works etc needed during our projects, or need recommend to clients people who can deal with such things.

Cheers.

[flowjoe]

Cheers Ability

Details have been sent

[Tony McC]

Are we sure that it is FOUL water being sent to this soakaway? Foul should never go to a soakaway, but should go to a septic/treatment tank or to the public sewers.

FlowJoe is right, though. It really shouldn't matter what is used as a surfacing, a soakaway should soak away. If it doesn't, then the construction of the soakaway is wrong and the surfacing has nowt to do with it.

[TheRobster]

I'm not sure that a soakaway should ever be put under a macadam surface......I would have thought there was a good chance of ground settlement/soil washout leading to subsidence which could cause sinking at the surface....and lots of cracks in the tarmac!

Also, are you sure the soakaway is taking foul drainage? It should only be surface water. The only foul drainage soakaways I've ever come across are leach fields and they are very different from a standard surfacewater soakaway.

Further, if it floods you're going to have problems. Once the surface is tarmac'd then where is the water going to go when the soakaway reaches capacity? Either out of the top of the manhole (flooding the carpark) or it will backup the pipes leading to the soakaway and flood somewhere else on the site.

Sounds to me like the builder doesn't really know what he's talking about. Did he do any site infiltration tests before he installed it? Does he even know if the site is suitable for infiltration?

[Tony McC]

There are specs available now showing constructions for sub-carriageway soakaways and all the maths show they should be ok, but, as with many new developments in the construction industry, only time will tell. Look at how they told us in the 1960s that concrete hi-rise was the future!

[TheRobster]

Tony,

I have not heard of these new specs - do you have any links handy so I can have a quick look?

I would say though that most developers will be wary of any new specs such as this and most will stick with the minimum clearance of 5m from any foundations until it's been proved that the new specs actually work. My own experience of developers is that they are generally very risk-averse and don't like using unproven techniques.

[Tony McC]

Rob - Charcon have published them in a PDF - I'm hoping to persuade them to sponsor a page showing an actual driveway construction using this product.