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Protection of trees on development sites

Protection of trees on development sites

and

AS4970

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Critical Root Zone

Root Protection Area

Optimal Root Zone

Tree Protection Zone

Matheny & Clark

Coder

British Standard

Barrell: SULE

Barrell: Tree A-Z

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Definitions

Tree

Long lived woody perennial plant greater than (or usually greater than)

3 m in height with one or relatively few main stems or trunks (or as defined

by the determining authority).

Preliminary Arboricultural Report

Guides the development layout

•Lists all trees

•Rates the trees – Suitability for retention

e.g. Unsuitable, Low, Medium, High

•Suitable trees to be marked on a plan with TPZs

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Arboricultural Impact Assessment

Submitted with planning application

•Lists all trees, identifying those to be removed and

those to be retained

•Identifies encroachments into TPZs and other impacts

•Recommends design and construction measures to

minimise impacts

•Specifies tree protection measures

•Includes the Tree Protection Plan, which should

accompany all construction documentation

Tree Protection Zone (TPZ)

What is it?

How big is it?

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Tree Protection Zone (TPZ)

TPZ = DBH x 12

DBH is Diameter at Breast Height

Diameter at breast height (DBH)

The nominal trunk diameter at 1.4 metres above ground level

determined from the circumference of the trunk divided by pi (π)

(see Appendix A).

Tree Protection Zone (TPZ)

TPZ = DBH x 12

DBH is Diameter at Breast Height

Diameter at breast height (DBH)

The nominal trunk diameter at 1.4 metres above ground level

determined from the circumference of the trunk divided by pi (π)

(see Appendix A).

If the proposed encroachment is less than 10% of the area of the TPZ and is

outside the Structural Root Zone (SRZ), detailed root investigations should

not be required. The area lost to this encroachment should be compensated

for elsewhere and contiguous with the TPZ. Variations must be made by the

project arborist considering relevant factors listed in 3.3.3.

The figures in Appendix D demonstrate some examples of possible

encroachment into the TPZ up to 10% of the area.

Minor Encroachment

<10% TPZ Area

and

Outside SRZ

Structural Root Zone (SRZ)

SRZ radius= (D x 50)0.42 x 0.64

D is Diameter immediately above the root buttress (in metres)

• SRZ for trees less than 0.15 m diameter is 1.5 m.

• SRZ formula and graph do not apply to palms, other

monocots, cycads and tree ferns.

• SRZ formula and graph do not apply to trees with an

asymmetrical rootplate.

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If the proposed encroachment is less than 10% of the area of the TPZ and is

outside the Structural Root Zone (SRZ), detailed root investigations should

not be required. The area lost to this encroachment should be compensated

for elsewhere and contiguous with the TPZ. Variations must be made by the

project arborist considering relevant factors listed in 3.3.3.

The figures in Appendix D demonstrate some examples of possible

encroachment into the TPZ up to 10% of the area.

Minor Encroachment

<10% TPZ Area

and

Outside SRZ

If the proposed encroachment is greater than 10% of the TPZ or inside the

Structural Root Zone (SRZ), the project arborist must demonstrate that the

tree(s) would remain viable. The area lost to this encroachment should be

compensated for elsewhere and contiguous with the TPZ. This may require

root investigation by non-destructive methods and consideration of relevant

factors listed in clause 3.3.3.

Major Encroachment

>10% TPZ Area

OR

Inside SRZ

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The tree protection process relies on good communication.

It should begin with an onsite meeting.

Planning Permit Conditions

1. A Tree Protection Zone (TPZ) must be observed at a distance of the following:

XXX metres in a radius surrounding the XXX tree (Common Name) within the front setback

from XXXXX, in front of Town House 1; and, XXX metres to the north and XXX metres to the south of

the XXX tree (Common Name) between the edge of the footpath and the kerb and channel.

2. Prior to the commencement of the development herby permitted a Tree Protection

Fence defined by a 1.8 metre (or larger) high temporary fence constructed using steel or timber posts

fixed in the ground or to a concrete pad, with the fence’s side panels to be constructed of cyclone

mesh wire or similar strong metal mesh or netting, must be erected around the XXX Tree (Common

Name) and the nature strip tree, the XXX Tree (XXX) at the distances specified for the TPZ.

3. The following must be observed within the TPZ area (without the further consent in writing

of Council’s Vegetation Management Officer):

a) the existing soil level must not be altered either by fill or excavation;

b) the soil must not be compacted or the soil’s drainage changed;

c) no fuels, oils, chemicals, poisons, rubbish and other materials harmful to trees

are to be stored or dispersed;

d) no storage of equipment, machinery or material is to occur;

e) open trenching to lay underground services e.g.: drainage, water, gas, etc.

must not be used;

f) tree roots must not be severed or injured;

g) machinery must not be used to remove any existing concrete, bricks or other materials;

4. All tree pruning work must be in accordance with the Australian Standards AS4373 (2007) “Pruning of

Amenity Trees” and be undertaken by a qualified and experienced Arborist.

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