Soakaway slumpping into ground (Depression)

magnethead

A friend of mine tells me the soakway in his garden has slumped over the years and he had to throw a load of fill on top of it to level it off.

Is it inevitable that say over 20years, with rainwater going into it, that a soakaway will slump a bit? or are you going to say there is such a think as a 'properly designed' soakaway where this does not happen?

Thanks

Metric Tensor

No reason for it to happen if the material that makes up the soakaway is properly compacted on installation.

Of course that means buying or using slightly more expensive fill material that remains porous after compaction.

In a domestic setting many people are unlikely to want to pay for proper drainage material so make do with what they have at hand and further more install it in a rush it as an afterthought without protecting the area with geotextiles, etc. With all that in mind what you described is quite possible.

The question to ask is where did the "slumped" soil go? The likelihood is into the voids in the drainage material thus making it less effective.

P.S. If you fancy some light reading have a look at BRE 365!

T-Maxx

Could be 'ecocells/aquacells' or the like which have collapsed.

Sacrolyte

It’s very common

magnethead

What an excellent reply, Metric Tensor I spoke to my friend again and he said ....GeoTextile what?? he said the way it was done back in the day, was large stones at the bottom, slightly smaller stones after that and then finished off at the top with sand....He has filled it in many times since, and even now you can see the big slump in the middle of his garden.

I can see why this is so common a problem now.

Would you hazard a cost on a properly done soakaway around this size?



Thanks

Metric Tensor

Sorry. It can be very hard to predict prices for small civil type works like this because it's very variable and depends on access, ground conditions, buried services, etc etc. Somewhere in the mid four figures I'd guess!

Get recommendations for a good local "digger man" and approach him for a price/estimate.

magnethead

Thanks again, I appriciate the advise, wow, looks like a decent sum of money.

It wouldn't be as frustrating, if I didn't live 200m from the sea and the Storm drain is outside my door
But regulations are regulations and everyone needs to be plastered with the same brush.

Metric Tensor

You mean your friend lives 200m from the sea! ;-)

Metric Tensor

P.S. If there's a storm drain outside the door you should be able to apply to the local authority for permission to connect to it. Although they might require attenuation and have charges that would amount to the same cost as the soakaway.

magnethead

Haha, Nope my old friend has the dodgy soakaway,
I'm 'maybe' putting one in my new build, it was a condition of the planning. Not sure I can argue with these folks. They get quite contrary when questioned.