Adam, Rob and all,
The way in which the sample result has been compared to the sgv is certainly
not precautionary and does reduce the area in an unsound way in my opinion.
I ran the results through clea (sample size of 4 for the said area) and the
max value was double the sgv. According to the guidance this means that
either a remediation strategy is needed for the whole area or further
sampling. The outlier test indicated that the result was not due to a
"hotspot".
The consultants proposal is to remediate the area only around the max result
that exceeds the sgv, as a "precautionary measure". If the 95th percentile
is used as it should be then the entire area needs further work. Therefore I
wouldn't agree with the area of remediation! Insisting on the max value test
would mean that further samples are required.
In this case i wouldn't agree the proposed area of remedaition but maybe the
consultants method has worked on other sites?
regards,
Michael Williams
Technical Officer
Tel: 01362 656334
Fax: 01362 656266
[log in to unmask]
Mike,
Rather than calculatethe 95th percentile and compare to the sgv the
consultant has taken the maximum sample values of contaminants found during
the investigation and compared these directly to the sgvs avoiding the
maximum value test.
I would agree with adam this cant be precautionary can it? as it most likely
reduces the area of remediation in an unsound way.
However, do you agree with them on the area of remediation? If so there may
not be much to argue about. I must admitt I have never had a consultant
carry out the 95% tile I suppose this is because our sites are generally
small and the main argument is usually about the quality and extent of
testing. May be insisting on the test would help increase the number of
samples (not sure).
ps as I biologist we allways N=3 was the absolute minimum and n=5 was
desirable 10 was luxury!!!
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