A little late with the response on cover systems (sorry), however, our
standard approach in Bury is as follows:
All cover systems should be based on the site specifics, so the depth
and requirement for capillary breaks etc will be considered. For simple
cover systems in private residential gardens with plant uptake, we
generally require a minimum 600mm of cover with a physical/marker break
layer at the base. The principle reasons for this is two fold. The
first is that the root systems for grasses and shrubs is typically up to
600mm and for those that exceed this the break layer should act as a
barrier. Secondly, most people will not dig deeper than 600mm in
typical gardening activities and also the break/marker layer should act
as a reminder to the resident (where told by responsible developers!)
not to go deeper or at least get them wondering why its there and check.
This does not cover all eventualities and we see it more as best
practice rather than 'belt and braces'.
For managed areas (landscaping etc) we require a minimum of 300mm cover
and break layer. Where trees/shrubs are to be planted we also recommend
deeper cover and/or tree pits of a size required by the tree type.
As for validation we recommend the following (which although is greater
that other posts, when you consider how much topsoil is actually placed
'thinly' across gardens it works out around 1 sample per garden or less,
dependant on how pokey the gardens are!):
Any soils being brought onto site for use in gardens or soft landscaping
areas will require validatory testing to be carried out to ensure
suitability. We recommend that an appropriate testing regime of these
materials is carried out and should include heavy metals, speciated PAH
and other tests dependant on the source of the soil material (such as
asbestos screen). The selected testing regime and screening values used
for assessing the results shall require approval from this Section. An
appropriate frequency of testing should be carried out to give
statistical confidence of the validation results. For garden areas we
generally accept a topsoil sample frequency of 1 per 50 cubic metres and
a subsoil sample frequency of 1 per 200 cubic metres or a minimum of 3
samples per soil type to give statistical confidence, which ever is the
greatest. For landscaped areas we generally accept a topsoil sample
frequency of 1 per 200 cubic metres and a subsoil sample frequency of 1
per 250 cubic metres or a minimum of 3 samples per soil type to give
statistical confidence, which ever is the greatest.
The topsoil should also conform to BS3882 Specification for topsoil and
the source recorded.
The final thing we ask developers to do is to record the 'protection
measures' placed at the property in the seller pack / lease agreement.
This is particularly useful when Mr & Mrs Jones decide they want a
lovely new conservatory (falls under to scope of development control)
and hopefully then don't end up with contaminated soils spread around
their garden from the foundation excavations!
Hope this helps, although clearly discrepancies between different
Authorities - sorry consultants/developers!
> Regards,
> John Naylor
Senior Environmental Protection Officer
> Bury M.B.C.
>
> *: 0161 253 6392
> *: 0161 253 5563
> *: [log in to unmask]
* Environmental Services, Textile Hall, Manchester
Road, Bury BL9 0DG
* www.bury.gov.uk
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Gareth
Rees
Sent: 01 August 2007 13:05
To: [log in to unmask]
Subject: Re: Clean Cover Validation
hi
For gardens with vegetable uptake I generally ask for 600mm of clean
material as this means the root zone for most plants is covered thereby
breaking the vegetable uptake pathway
For properties without the vegetable uptake pathway I ask for a cover
layer in accordance with BRE 465 COVER SYSTEMS FOR LAND REGENERATION
As for sampling with reguards to validating the imported material is
clean I ask for 1 test for every 500m3 of imported material
Gareth Rees
Contaminated Land Officer,
Harborough District Council,
Tel: 01858 821174
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Mark A
J Edwards
Sent: 01 August 2007 12:20
To: [log in to unmask]
Subject: Clean Cover Validation
All,
I am attempting to develop a consistent approach for developers with
respect to the thickness of clean cover for contaminated land and the
sampling frequency for validation/verification purposes. Any/all
contributions gratefully received.
thanks
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