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19/09/2014
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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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