advice pls on soakaway walls

[karaman]

hallo,

am buildfding a rainwater soakaway 2m deep x 1.5m wide x 2m long

i would like to build concrete walls on its inside - my soil is sand (an old lake bottom). i think if i dont then the sand from the sides will crumble into the pit and i can start excavating again (ugh).

QUESTION
1. how thick should the concrete walls be
2. is mixture 3sand : 1 cement ok for the concrete or should it be stronger like 2sand : 1 cement
3. am i right in thinking the walls should have holes in them so the surrounding sand can drain into the pit and if so how big and what spacing should the holes be

cant think of any other questions

thanks for help

karaman

 

[freddiemercurystwin]

There is no need for walls generally, you just surround the fill with a geotextile membrane that allows the water to pass through but not the fill/earth. If you built walls around it they would have to be built as super thick retaining walls in case it runs dry.

 

[stuart45]

You can buy concrete soakaway rings.

 

[^woody^]

How do you know that you need a soakaway of those dimensions? If the soil is granular (ie sand) then it will be free draining anyway

 

[karaman]

thanks for replies

- i'm not an idiot, wouldnt start hard graft if i didnt need a soakaway
- cant pay squillion/trillion for delivery of ready made rings and it couldnt get to the back of the garden anyway
- idea is to use materials i already have to hand

maybe i'll make my own rings

thanks for replies

karaman

 

[freddiemercurystwin]

There is no need for walls generally, you just surround the fill with a geotextile membrane that allows the water to pass through but not the fill/earth. If you built walls around it they would have to be built as super thick retaining walls in case it runs dry.

 

[karaman]

freddymercurystwin,

thank you. i get the message the second time around - i dont have to build
anything just buy some membrane.

the pit does run dry in summer, we often get 30-35 for a week or so maybe two/three times a summer.

QUESTION
should the membrane cover the sides only or the bottom as well and if the sides only is it ok to keep it in place with a few bricks at the bottom and cover it with earth at the top. i know the answer must be obvious to you but i have no idea......

thanks

karaman