Installation of Kerbs within the root protection area.

[Andrew B]

Hi there,

 

Does any one have an arb method statement for the installation of kerbs within the Rpa and the installation of porous bitmac. The proposal is to replace an existing road at the side of a school.

 

Any advice or specs would be brilliant.

 

Andrew

[Tim Williams]

Follow NJUG 10 and BS 5837 trees in relation to construction. Ideally any digging within RPA should be done by hand or using Air spade etc. There are numerous different ways to do this. Does it need to be full kerb stones or could the edge be of a different construction as i assume it's a private/unaddopted road.

[Andrew B]

Thanks,

 

Giles has given me a good head start on this aswell. The road is unadopted but is within a conservation area.

 

Andrew

[AA Teccie (Paul)]

Hi there,

 

Does any one have an arb method statement for the installation of kerbs within the Rpa and the installation of porous bitmac. The proposal is to replace an existing road at the side of a school.

 

Any advice or specs would be brilliant.

 

Andrew

 

Hi Andrew,

 

I'm not sure it would be down to the 'arb' to produce the MS here but more the role to input to the highway engineer spec for kerb installation within the RPA (or actually perhaps it would). The arb would sya what can and can't be done and the engineer would come up with a design solution.

 

In Cheltenham previously, this included 'molding' (for the want of a better description) concrete around tree buttress roots which had deflected and pushed the existing kerbstones out into the carriageway resulting in several damaged tyre claims against the Council.

 

A 'compromise' solution whihc the highway engineer accepted would need to be re-done about every 3-5 years but it allowed retention of early mature Lime trees whihc formed part of an avenue, so were very important 'amenity' trees.

 

I'm sure there are 'arb consultants' out there who do have standard MSs for this situation, as it's not that uncommon IMO, but whether they're willing to share them is another matter as obvioulsy they will consider that to be part of their professioinal consultancy service provision to a 'fee paying' client....which is fair enuff!

 

NJUG Vol.4 & BS 5837 are good leads along with 'TRiBE' publciation ('Tree Roots in the Built Environment').

 

Good luck..

Paul

[Andrew B]

Thanks for the info paul.

 

cheers,

 

Andrew

[Callum]

Hi There

 

I've just been looking at NJUG Vol 4 and have a question.

 

The tree protection zone is divided into 3 different zones: the prohibited zone (within 1 metre of the stem), the precautionary zone which extends to 4x the tree circumference, and the permitted zone which is outside the other two.

 

Does anyone know if '4x the tree circumference' means 4x the stem circumference (and if so at what height) or is it 4x the circumference of the whole tree (seems a bit over the top)

 

How does this compare with the BS:5837 root protection area (12 times the DBH).

 

Thanks in advance.

Callum

[Andrew B]

Hi there,

 

The x4 measurement refers to the stem circumference. The difference between the two measurements is not that much.

 

if you had a 50cm diameter tree then the root protection radius, which is used to work out the area would be 6m.

 

The Njug calculation would give a radius of 6.28m

 

Not much difference really.

 

The measurement should be taken at chect height or base for multi-stemmed trees.

 

correct me if i am wrong guys:001_smile: I dont mind.

 

Cheers

 

Andrew

[Giles Hill]

It's 4 x the stem circumference measured at 1.5m above ground.

 

The protection zone for NJUG 10 based on 4x stem circumference is approx 9% greater than the root protection area for BS 5837: 2005 based on 12x stem diameter.

[Giles Hill]

You beat me to it Andrew, while I was checking the 9% thing.

[Amelanchier]

The small difference is because both seek to calculate the same area but based upon different dimensions of the tree. Because the circumference is obtained by multiplying the diameter by pi (3.14...) you can reverse the equation by dividing your BS5837 multiplier by pi (or 3 which gives a more usable round number)!

 

Diameter (or circumference / 3.14) x 12 = circumference (or diameter x 3.14) x 4

 

The variation occurs because pi has been rounded down to three - just like in the bible.