Soakaway advice needed

Foul and surface water, private drains and public sewers, land drains and soakaways, filter drains and any other ways of getting rid of water.
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dan90
Posts: 4
Joined: Thu May 07, 2020 8:52 am
Location: Staffordshire

Post: # 118589Post dan90

How about this one chaps, any insight on this would be appreciated - having no experience just need a bit of guidance as to whether I'm being over cautious or whether it ain't worth the risk!

Planned on putting in garden drainage for a 30m2 garage and 20m2 of paving - original plan was to install 1.6m3 crate giving an additional 50% (garage is to be reduced in size in the coming years by at least half also) - as the crate size suits the plot and an additional crate might as well go in as the holes going to need to be that big anyway.

Dug out to 1.3m deep for the install, all was looking well until the last 100mm when we started to get a bit of clay appearing - dug down a 300mm2 hole 500mm deep in the 1.3m pit and we've hit clay.

Filled the 300mm2 hole with water at 5pm and was drained by morning - ran percolation test 24 hours later and passed (JUST) although still about 2inch of water there this morning (14 hours later). Am I going too deep here would I be fine to just run my percolation test to the depth of the Soakaway? Crate we're putting in if we proceed would be 1m wide x 2m long x 0.8m deep - will be putting in 100mm clean stone, two 150mm of MOT type 1 with a final layer of 150mm MOT Type 1 with paving laid above.

What are you thoughts, would be appreciated - is it a risk not worth taking? Or will the additional space in the crate and the 1.3m of decent soil on top make it a safe bet, especially if the percolation test passes when ran at the depth of the base of the Soakaway (will be 300mm below the incoming pipe).

Many thanks in advance

dan90
Posts: 4
Joined: Thu May 07, 2020 8:52 am
Location: Staffordshire

Post: # 118591Post dan90

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Tony McC
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Post: # 118595Post Tony McC

Is 1.3m down from the ground level the invert level for your proposed crate installation? Assuming it is, I think you will be OK, as the water level (which may be the water table, but not nesser celery so) is 200-300mm below that, showing there is at least the possibility of water escaping from the crate.

100mm clean gravel below the crate, around the sides and over the top, then place your build-up sub-base layers 150mm at a time, thoroughly compacting each before placing the next...and Robert will indeed be your Father's Brother.
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dan90
Posts: 4
Joined: Thu May 07, 2020 8:52 am
Location: Staffordshire

Post: # 118597Post dan90

Hi Tony,

Thanks for the prompt response, appreciate it.

Drawn a little diagram of the job hopefully that's clearer - should my invert level be lower or is that suitable?

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Many thanks

Tony McC
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Joined: Mon Jul 05, 2004 7:27 pm
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Post: # 118600Post Tony McC

That looks fine - see: https://www.pavingexpert.com/drain13

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dan90
Posts: 4
Joined: Thu May 07, 2020 8:52 am
Location: Staffordshire

Post: # 118605Post dan90

Great thanks for that Tony really appreciate it, given me confidence!

Best get digging and finish this hole off then eh?

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