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Posted: Sun Jan 09, 2011 3:03 pm
by r44flyer
Hello,

Today I dug a pit to try and test the drainage of the soil in our front garden prior to converting it into a driveway (32sqm area). It will most likely be gravel over plastic cellular paving, or, perhaps, permeable blocks, but the soil suffers from a high clay content and I was worried about poor drainage.

So, the pit was about 550mm x 550mm x 300mm deep (0.3sqm area). I poured in a bit more than 40 litres of water, and it was gone in just under 40 minutes. How does that sound? Good or bad?

Posted: Sun Jan 09, 2011 6:43 pm
by Tony McC
VERY good.

The essence of the standard simplified test is a hole 300x300x300 at least 1m above the water table. Fill and leave it overnight. If it's empty the next morning, the ground is deemed to be sufficiently permeable for driveway/patio installations.

And before anyone starts, I *know* there's more to BRE 65 than that, but this is the widely accepted simplified version.

Posted: Sun Jan 09, 2011 8:44 pm
by mickg
that's exactly what i was going to post with the dimensions of the hole :D

Posted: Sun Jan 09, 2011 9:59 pm
by r44flyer
Jolly good! I had no idea what was sensible, and to be honest I was expecting the clay to give me a nice low level bird bath.

Thanks again.

Posted: Sun Jan 09, 2011 10:09 pm
by GB_Groundworks
http://www.klargester.ie/download-files ... ystems.pdf

Detail info on percolation test from klargester, they recommend filling it once letting it drain then doing the test

Posted: Mon Jan 10, 2011 8:58 am
by Tony McC
Yes: the 'fill and fill again' method is edging closer to BRE 65.

The incredibly affable Prof. John Knapton developed an incredibly simplified 10-minute test for soil permeability a couple of years ago. He reckons it's good enough to use as an indicator for domestic driveways and patios. I had the details on my desk while I was writing the new stuff about soakaways, but since the xmas tidy-up, I can't find a bloody thing. It must have been moved to another pile....I'll see if I can find it later today.