UKTC Archive

RE: AAGN12 - Guide to the use of cellular confinement systems near trees

Subject: RE: AAGN12 - Guide to the use of cellular confinement systems near trees
From: "Weal, Mark"
Date: Oct 29 2020 10:57:55
The 2020 APN12 states: A tracked excavator with a grading bucket is normally 
the best machine to use to remove the turf layer because this creates an even 
surface. For this application excavators should be of an appropriate size for 
delicate works (i.e. ≤5tonne). Ground preparation works using excavators in 
root protection areas must be supervised by an arboriculturist to make sure 
that significant roots (single roots >25mm diameter or clusters of roots 
10–25mm in diameter) are preserved and to ensure that vehicles are being used 
appropriately. Where there are deep soils it may be possible to remove more 
than 50mm from the surface, but care is essential because a large proportion 
of the root system is likely to be near the soil surface. Surface skimming 
must be stopped immediately by the supervising arboriculturist if the upper 
side of any significant tree roots is exposed. Even though the ground is 
broken by such works this approach may still be described as ‘no-dig’ in the 
context of installing hard surfacing near trees – the crucial distinction is 
that the standard practice of installing sub-surface foundations by replacing 
soil with compacted stone aggregate is avoided when a cellular confinement 
system is used.

I’m somewhat surprised we are still recommending this. But it’s ok…once the 
excavator has skimmed the top off the surface roots, the Arb will stop it. 
And it’s only for excavators up to 5t. Surely they can’t do too much damage?!
And so much for their definition of no-dig…There was me thinking that no-dig 
solutions were to prevent damage to tree roots.

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info <uktc-request@xxxxxx.tree-care.info> 
On Behalf Of Jerry Ross
Sent: 29 October 2020 10:45
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: AAGN12 - Guide to the use of cellular confinement systems near 
trees

Useful to have a guide to supersede the venerable APN12!
I'm not sure about the way it deals with uneven ground though, by piling up 
sharp sand or clean angular aggregate to fill in the dips. (par. 17, p9). A 
colleague of mine (who has laid acres of the stuff) recommends laying the 
geocells directly onto slightly uneven land and levelling
*above* the cells, and where there are deeper hollows, using thicker or 
doubling up the geogrid, as in the diagram attached.
It seems to make good sense to me to put the additional stone *above* the 
protective layer, not below it.



On 27/10/2020 14:32, Ben Rose wrote:
The new good practice guide for the use of cellular confinement systems 
near trees is now available. For those unfamiliar with cellular confinement 
systems, they can be used as temporary ground protection or to create 
low-impact surfacing near trees.

A free download of the document is available on the Arboricultural 
Association 
website:https://www.trees.org.uk/News-Blog/Latest-News/New-guide-to-us
e-of-cellular-confinement-systems-n

I hope that you find this guide to be informative and of assistance.

Best regards,

Ben








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