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Mark,

I attended the NHBC conference on 7th Nov that was co-hosted by British Sugar and they have come up with some pragmatic solutions that will greatly assist the testing of imported topsoils.  The suggested sampling/plot frequencies will be very useful as this was always a little uncertain.  What they have stated is that suppliers of topsoil will require a desk study as a minimum followed by either compliance with BS3882 if no potential sources of contamination are present or additional chemical testing if sources of contamination have been identified.  At the receiving site where no contamination is present, on site testing may not be required if a copy of the suppliers certification is provided that is relevant to the material being delivered, the frequency of testing is appropriate to the source and where there are good controls in place.  Skip waste derived topsoil will fall down on the majority of these criteria whereas good quality topsoil, such as the British Sugar supplied topsoil, may comply.  

NHBC have stated what their minimum requirements are, which might not be the same as is required by Local Authorities. I would always advocate some on site testing of imported topsoil, regardless of its source.  However the scale of the verification testing may be able to be reduced if good quality topsoil is imported that meets with the NHBC criteria.  

It is interesting to note that NHBC endorse the use of the BRE465 cover system model, which might lead on to another debate about soil mixing zone depths.  




On 26 November 2012 15:06, Mark Seaman <[log in to unmask]> wrote:
Afternoon all,

A local consultant has made me aware that the NHBC have just published revised guidance on validating cover systems / topsoil in issue 8 of Technical Extras:
http://www.nhbc.co.uk/Builders/ProductsandServices/TechnicalExtra/

I had a brief discussion with the consultant about the guidance and we shared the same concerns. Consequently I wondered whether list members were aware of the guidance and whether others had similar concerns. My concerns include:

1.      I can't agree that soils raised from agricultural land would not need testing (pesticides, herbicides, fungicides, fertilisers, PAHs (stubble burning) etc etc);
2.      I would also need convincing that any topsoil manufactured from a waste stream, green or not, would not require any testing at all (although in reality I guess it would probably be subjected to a certain degree of testing as part of manufacturer QA/QC?); and
3.      I cannot agree that imported topsoil which is, "...not being used as a cover system as part of a contamination remediation strategy..." will not require testing. There is no logic to that statement at all. If you place contaminated top soil over clean or contaminated subsoil the result is the same: a viable pollutant linkage. In my opinion a developer must be able to PROVE that ANY topsoil / subsoil imported onto site is suitable for the intended end use. If that use is residential then the chemical composition must be judged against current SGVs / GACs etc etc.

Maybe I’m being overly conservative so I would be very interested in other opinions. I’m not convinced that this document is very helpful and I expect that it will be cited in many validation reports to justify no / low level testing. I am curious as to how the HNBC formulate such guidance and whether any regulators etc are consulted during the process so if any NHBC list members could comment I would be very grateful.

Thanks,
Mark.

Mark Seaman
Waveney District Council
Environment Protection Officer
01502 523153
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website: www.waveney.gov.uk ( http://www.waveney.gov.uk/ )
twitter: www.twitter.com/waveneydc




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