Why not just place geotextile on top of the retained ash layer which can
be cut to the shape of the roots and fixed in place. Then place soil
over the top of the geotextile. The ash is now inaccessible and you
don't have to pile large thicknesses of soil over the top just the
standard 300mm.
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Neil
Brown
Sent: Monday, December 19, 2005 9:25 AM
To: [log in to unmask]
Subject: Remediation around protected trees
I've just joined this forum, so many apologies if this isn't the type of
query which should be sent to the list.
We have a development site which is historically contaminated with a
discrete ash layer about 300mm below the surface. The area is to be
cleared by removing the topsoil and ash layer and replacing with 'clean'
sub and topsoil. However, there are trees on the site protected by a
tree preservation order. The idea is that the ash layer will be hand dug
out around the trees and then topsoil added above the contamination to
provide a barrier. The area will be used as public open space within a
housing development.
What I'm looking for is guidance on what depth of soil layer should be
used to cover the ash layer to make it suitable for use as public open
space.
I've seen many values quoted ranging from 30cm-120cm. There's also the
issue of covering the trunk base of a tree in soil, which I'm sure can't
be good for them.
Does anyone have any experience of remediating around trees? Any help
would be greatly appreciated.
Neil Brown
West Lothian Council
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