Attachment D - Tree Management Plan

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                                                                  Contents

1.0 Introduction ...................................................................................................................................... 1
2.0 Australian Standard AS4970-2009 .................................................................................................... 2
3.0 Tree Assessment ............................................................................................................................... 3
4.0 Management..................................................................................................................................... 5




1.0 Introduction

Evans Built Pty Ltd has been engaged to reconstruct the clubhouse of Sunshine Beach Surf
Lifesaving Club. Works commenced in March 2019.

Electrical authorities require an upgrade to the reticulation serving the Club. This will
necessitate the installation of a new pole mounted transformer and trenching for conduits
across Webb Road Park.




Approximate location of new underground electrical conduits – Evans Built




Taylor Ecology                                     Tree Management Plan – June 2019                                         Sunshine Beach SLSC

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Noosa Council has expressed some concern as to the effect of these works on existing well
established Park trees and requires a written methodology from a qualified arborist to
ensure a minimisation of harm.

For this purpose the author – a Level 5 consulting arborist with some 44 years’ professional
experience – attended the site on the 11th June 2019 in company with the site manager to
confirm the extent of works.

The Tree Management Plan (TMP) which follows will primarily follow the recommendations
of the documents Australian Standards AS4970-2009 Protection of trees on development
sites and AS4373-2007 Pruning of amenity trees.



2.0 Australian Standard AS4970-2009

This Standard (Protection of trees on development sites) defines Tree Protection Zones
(TPZ’s) and Structural Root Zones (SRZ’s) of trees according to their diameter. While the
meaning of the SRZ is self-explanatory, the TPZ is defined as ‘an area isolated from
construction disturbance, so that the tree remains viable’.

The TPZ is determined as a radius by multiplying its diameter (measured at 1.4 metres
height) by 12 i.e.
                          TPZ radius = 12 x DBH (diameter at breast height)

For multiple stems the DBH is determined by the following equation –

                              Total DBH = √(DBH 1)² + (DBH 2)² +………

In general a TPZ is not to be encroached by more than 10% and then only under the
supervision of an appropriately qualified arborist, with compensatory measures to be
implemented. Encroachment exceeding 10% may be acceptable but only under the
supervision of the arborist.

Typical compensatory measures include watering and the use of mulch.

The SRZ is contained within the TPZ and is the area required for tree stability and is
illustrated on page 13 of the Australian Standard or numerically by the formula –

                 Radius = (50 x D)* x 0.64
                 Where D = Diameter of stem and * = 0.42

Note that the TPZ calculation is of necessity somewhat arbitrary and reinforces the necessity
for obtaining advice from the site arborist.




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At all times it is worthwhile that all relevant staff and contractors note the following
generalised illustration of typical tree roots (per Arboriculture – R. Harris, J. Clark and N.
Matheny).




Figure 1


That is to say there can be a loss of surface tree roots even beyond the TPZ and this has
implications for tree viability – particularly if those retained trees have moved beyond the
young and vigorous stage of life.


3.0 Tree Assessment
Although it is intended that trenching across the park will follow the existing conduit there
may have to be deviations according to site conditions revealed during works. There are 6
trees in total whose TPZ’s were assessed for impact.




Tree 1 adjacent to Club looking north



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Trees 2-6 looking west




In summary it is only Trees 1, 2 and 3 whose TPZ will be impacted significantly. In the case of
Tree 1 it is possible that the final trench location may be able to avoid the TPZ.



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4.0 Management

Where trenching has been flagged to impact the TPZ’s of Trees 1, 2 and 3 the project
arborist is to mark out a length of trench in those particular zones which must undergo hand
excavation as a minimum – and preferably vacuum excavation – to investigate the presence
of any significant roots. The balance of the trenching may be done mechanically.


                           Typical delineation between mechanical trenching
                           and root investigation area.




The following site procedure should be adhered to –

Under the supervision and presence of a Level 4 arborist or higher:

       Minimise any disturbance (stockpiling. traffic and parking) within any TPZ;

       Any uncovered roots are to be cut cleanly by the supervising arborist per the
        Australian Standard AS4373-2007 Pruning of amenity trees;

       Large roots greater than 30mm diameter which are encountered will require further
        root investigation within the TPZ by the supervising arborist before they are severed;

       Backfill works with on-site material with a minimum of delay;

       Supervising arborist will determine the necessity for compensatory measures within
        the TPZ such as mulching and watering;

       Noosa Council must be notified immediately should any unforeseen issues be
        encountered.


Mark Taylor


Taylor Ecology                  Tree Management Plan – June 2019            Sunshine Beach SLSC