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RE: Retaining wall drains

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Thanks Harold,

I specify drains also and backfill with DOT or geotech recommended 
aggregate. I didn't know if I was the only one relying on the drains to 
actually perform.

Will H

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Harold Sprague Sent: Saturday, December 08, 2012 7:49 PM
To: seaint-seaosc(--nospam--at)
Subject: RE: [SEAINT-SEAOSC] Retaining wall drains

I use drains.  I use 4" diameter PVC drains at 8'-0" o.c.  I also backfill 
with open graded aggregate (crushed rock or gravel).  The open graded 
aggregate should have no fines and can be anything from 3/8" to 1").  The 
open graded aggregate is wrapped with filter fabric to limit the amount of 
fines that can get to the drains.  I generally have a cap of soil on the 
top for planting.  I protect the drains with a #10 galvanized mesh to keep 
the drains open.

It is also easy to consolidate the aggregate with a walk behind vibrating 
compactor.  This puts a lot less pressure on the wall as opposed to 
compacting a clay soil material.

Eventually the drains will fill with fines, but that will be a long, long 
time from now.  I am old enough now to have seen buildings that I designed 
in the early 1980's be demolished to make way for some other project. 
.....oh well.

Regards, Harold Sprague

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