If you read P5-066/TR (model procedures on sampling) there is some
interesting stuff on averaging areas (AA). There is a distinction
between finding hot spots and characterising the chemical nature of a
given area.
The document states that an AA might be 1 garden (of 100sqm). If you
are investigating a large site you should set your Stage 1 sampling grid
to be the size of the AA (or, say 4-6 AAs). If you choose 1 AA, this is
an 11m square grid pattern of trial pits etc.
The idea is that you should pick up a hotspot equal in size to an AA by
doing this. This tells you it exists but does not tell you anything
about the concentrations across the AA, just that there is a hotspot
which could be the same size as a garden. This is, of course subject to
given confidence limits.
The guidance goes on to say that if you want to characterise an
individual garden, you must do a Stage 2 investigation at a closer grid
spacing. The concept of Smallest Area of Concern (SAC) is discussed.
If the SAC is 25sqm, you will need a 5.6m grid spacing.
Guidance on Pgs 62-63 of that document is helpful in terms of the sort
of situations where very detailed sampling would be required.
There is also an interesting paper on AAs and the CLR7 tests by Paul
Nathanail in the Quarterly Journal of Engineering Geology and
Hydrogeology (2004) vol. 37, 361-367.
Regards,
Kevin Privett.
Dr Kevin Privett
Principal Geo-Environmental Consultant
Hydrock Consultants Ltd
Over Court Barns
Over Lane
Almondsbury
Bristol
BS32 4DF
Tel: (01454) 619533
Fax: (01454) 614125
[log in to unmask]
Cell phone: (07799) 430870
Offices in Bristol, Plymouth, Northampton, Stoke-on-Trent.
www.hydrock.com
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-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Ivens,
Rob
Sent: 22 December 2005 12:09
To: [log in to unmask]
Subject: Re: CLR7 and averaging areas
I do not think that evy garden is reasonble as a first point of
approach.
We are currently doing 2 sites under part IIA.
Site 1 has 22 houses and guide hut.
site 2 has a total of 500 houses and an effec ted area of ~200 house The
current area of inspection is 60 houses.
We have commissioned ESI to provide us a statistical model to help us
a. assess the confidence that will be achieved by the initial SI
b. how much more SI do we need to do to improve that confidence to a
reasonable level.
c. identify good bad and unknown areas.
I would argue that once you have achieve a reasonable level of
confidence across the site you should only need to up the dat collection
in the unknown/grey areas.
ps our initial SI on the 21 houses cost 7k for 12 Window sample
locations
the pahse II shallow surface SI cost a further ~20k and the avaerage
number of inspection points per property = ... well you guess.
So much to read.
So Little Time
Rob Ivens MVDC- 01306 879232
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]]On Behalf Of adamc
czarnecki
Sent: 22 December 2005 11:01
To: [log in to unmask]
Subject: Re: CLR7 and averaging areas
Phew, three to four samples per garden. Even if you did this is it
really statistically robust? So are you suggesting deriving upper 95%ile
from this data for EACH garden plot. I have seen some sites where the
"consultant" has adopted this strategy, but do you honestly believe it
is pragmatic or reasonable to do so?
PS Merry Xmas everyone.
Adam
Balmer, Brad P wrote:
>My view would be that if you wish to consider the gardens individually
>on this basis you do not have enough data to make an assessment and you
>should have the consultant recover 3-4 samples per garden this will
give
>you enough data to have an averaging area for each individual garden.
>
>-----Original Message-----
>From: Contaminated Land Management Discussion List
>[mailto:[log in to unmask]] On Behalf Of Wendy
>Lilico
>Sent: Thursday, December 22, 2005 9:18 AM
>To: [log in to unmask]
>Subject: CLR7 and averaging areas
>
>I have asked this question a while ago and got some useful answers but
>can I be a bit more specific this time....
>
>I have a large housing development subject to a remediation scheme
which
>includes testing soils prior to importation and again once the material
>is in-situ (on the basis of one sample every 2-3 plots). This is my
>preferred system as it guarantees that the material is the same, or at
>least as 'clean', as the material tested at source but source testing
>avoids importing clearly unacceptable material in the first instance.
>
>Anyway there have been a number of in-situ samples which have come back
>with results over the SSTLs for one or two determinands (usually zinc,
>boron or nickel). The consultant originally proposed that the whole
>volume of soil imported from a single source should be considered a
data
>set for the mean and maximum value tests and, whilst that may appear
>reasonable in theory, in practice it involves a large area of the site
>with discontinuous plots often at considerable distance from the
>'failed' sample. It is my opinion that once the material is placed it
is
>academic if the material at distance from the individual plot is
>acceptable - it is the exposure of the receptor at that particular plot
>which is important ("an averaging area (or area of
>interest) is that area (together with a consideration of depth) of soil
>to which the receptor is exposed or which otherwise contributes to the
>creation of hazardous conditions" CLR7)
>
>The question then is what is a reasonable 'averaging area' in these
>circumstances?? I draw a clear distinction between a planning
assessment
>and a Part IIA assessment where it will usually be necessary to test
>each area of ownership to a sufficient extent to make a definite
>determination of whether it is 'contaminated land'.
>
>Any comments would be much appreciated as usual.
>
>Meanwhile may I take this opportunity of wishing you a very happy
>Christmas and thanking you for all the help and advice throughout the
>year. I personally find this forum invaluable - and even entertaining
on
>occasions - what more could you want for Christmas !!
>Cheers
>Wendy Lilico
>Principal Environmental Health Officer (Pollution) Development and
>Environment Darlington Borough Council
>11 Houndgate
>Darlington DL1 5RF
>Directline (01325) 388570
>Mobile 0779 088 4198
>Fax (01325) 388555
>email: [log in to unmask]
>
>
>
>
>
>
>
>
>
>
>
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