I agree with the points made by Simon and Karen.
BR465 does have appropriate applications in some situations - where soil contaminant concentrations are sufficiently elevated in comparison to screening values as to warrant some form of remediation, but where they are low enough that hard engineering, excavation and removal, or in-situ remediation are over the top.
The document does have mechanisms within the process to indicate where it is appropriate to consider a natural mixing scenario.
I would particularly draw your attention to smaller residential sites where, for example, the health risks from a low level of PAH concentrations in generic made ground which may slightly exceed screening levels can be adequately mitigated by introducing a suitable soil cover.
Where there is no risk to groundwater, concentrations are not grossly elevated, and there are not obvious hotspots, why overcomplicate the solution?
Jon Archer
Senior Geoenvironmental Engineer
Harrison Group Environmental Limited
Kimberley Street
Norwich
NR2 2RJ
Tel: 01603 613111
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-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Clennell-Jones, Simon
Sent: 25 August 2010 13:15
To: [log in to unmask]
Subject: Re: BRE: BR 465
BRE454 tends to be given as the source of the various capping
thicknesses (typically 600mm but variable dependent upon end use). The
issues around the potential for mixing of 'clean' soil is also my
understanding of the reasons that the EA 'withdrew support' but I am not
aware of anyone else publishing guidance on thicknesses of clean cover.
To be honest, I am a little confused as to why people turn their noses
up at this particular document - anyone care to elaborate on their
scepticism or have any alternative data or guidance on the thicknesses
of cover which should be used?
Is there any particular reason why 'dilution' in this sense (if mixing
were to occur through the action of a householder) is 'bad' compared to
the sustainability implications of importation of greater volumes of
'clean' soil to a site when the risks to the end user are still likely
to be of the same magnitude? Or is the concern that the mixing
considered in the document is unrealistic?
Simon
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of David
Dunkley
Sent: 25 August 2010 12:48
To: [log in to unmask]
Subject: Re: BRE: BR 465
We had an interesting conversation with a contaminated land officer
about
the BRE document:
The spreadsheet to calculate the thickness of capping considers the
concentration of contaminants in the existing soil and uses this and
knowledge of the concentrations in the cover system to derive a
thickness.
Apparently, the thinking behind this is that any mixing of the capping
and
contaminated soils will result in the near surface soils remaining below
the
guideline value. Therefore a particularly 'clean' capping could be
thinner
than the one where concentrations are slightly higher. As this approach
accepts that mixing of clean and contaminated soils, there is an issue
with
potentially contaminating clean material, which is frowned upon.
Apparently
this was the reasoning for the EA to withdraw support for the document.
I am unsure on whether any of the above is correct, but it was something
we
were told during a conversation about a particular site. It would be
interesting to hear views on this.
It doesn't help though!!
David
David Dunkley B.Sc. (Hons)., CEnv, M.S.E.E., FGS
Senior Geo-environmental Engineer
Cedar Barn
t: 01604 781877
White Lodge
f: 01604 781007
Walgrave
m: 07900 006688
Northamptonshire
e: [log in to unmask]
NN6 9PY
w: www.soiltechnics.net
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-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of
Russell
Corbyn
Sent: 25 August 2010 12:34
To: [log in to unmask]
Subject: Re: BRE: BR 465
No.
We've had it since 2004 or whenever it came out and it is about as much
use
as a fish's fart.
Loving the bit in the table where it says "areas where rabbit or badger
populations are significant."
Significant rabbits? Bwaaaa! Is that 1 in 10,000 or 1 in 100,000 ???
:)
Russell
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Clive
Williams
Sent: 25 August 2010 12:13
To: [log in to unmask]
Subject: Re: BRE: BR 465
The answer is invariably 600mm
there is an email [log in to unmask] on the Powerpoint (this
powerpoint
is fab for graphics)
Does anybody see much use of this document? I'm fairly sceptical of it
but
with th elack of anything else.......
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