Hi Adam and all,
 
Is this another conservative element built in to CLEA? or does this mean that we should all be insisting on a minimum cover depth of 1.15m where SGVs are exceeded? 
 
If it is the latter, this places a heavy cost burden on development and even more a hit on sustainability (final finished levels through planning could lead to more going to landfill, never mind trying to source clean soils). 
 
I think we need a few more tools in the kit bag to answer to marginal contamination typically encountered or the majority of sites, the key one being bioavailability for a range of common contaminants (inc PAHs).
 
Regards
 
John
-----Original Message-----
From: Adam Czarnecki [mailto:[log in to unmask]]
Sent: 07 August 2007 10:50
To: Naylor, John; [log in to unmask]
Subject: RE: Clean Cover Validation

It may be worth pointing out that CLEA UK model defaults to an assessment of the source at a depth of 1.15m.

 

Adam

 

 

 

--

Adam Czarnecki

Head of GeoEnvironmental Division
Clancy Consulting Ltd.
Dunham Court
2, Dunham Road
Altrincham
Cheshire
WA14 4NX

Tel: 0161 613 6000
Fax: 0161 613 6099

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Registered Office: 2 Dunham Road, Altrincham, Cheshire, WA14 4NX
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From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Naylor, John
Sent: 07 August 2007 10:27
To: [log in to unmask]
Subject: Re: Clean Cover Validation

 

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
8     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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