Development Application Part 2 - Environmental & Stormwater Management Plans · OPW11/0335

Matrix Projects (QLD)- Essence of Peregian, David Low Way Peregian Beach QLD 4573      Page 10



        If there is cause for concern and further details are required for a full
        assessment then the use of diagnostic tools such as Resistograph ® Picus®,
        increment borers, soil excavation for root assessment, and Fractometer®
        testing are used. From either the initial visual assessment or the use of
        diagnostic tools, failure criteria may be given for each tree assessed, and an
        informed decision is reached for recommendations.

        VTA may be used to state to what extent a defective tree is at greater risk of
        breaking or failure, compared with a completely sound one. In QTRA this is
        shown as the PoF or in retention value this may result in it lower value.

4.2     Tree Protection Methods and Roots
        Tree protection involves the minimising of damage to the tree's root and
        vascular system during activities such as construction or installation of root
        barriers, thus reducing the chance of tree health decline or death, and the
        possible damage to the structural stability of the tree from root damage.
        Failure to maintain a minimum tree protection zone may result in declining
        long term vigour, health and structural stability in a tree on a construction site.
        All trees to be retained on a construction site should have protected root zones
        that are measured off the DBH of the trunk via either the Matheny & Clark
        (Harris 2004, & Matheny & Clark 1998) formula, the British Standards (BS
        5837:2005) for protecting trees, or the newly released Australian Standards
        (AS 4970-2009 Protection of Trees on Development Sites).

        Using the Matheny & Clarks method a previous understanding of a tree
        species tolerance to disturbance (good, moderate, or poor) is required to work
        out the Tree Protection Zone (TPZ). This distance calculation is simplified
        under BS 5837:2005 where a trunk diameter (DBII) times 12 is used, the same
        for AS 4970-2009. Therefore for this report and management of the tree
        protection during development, the measurement of TPZ is taken from AS
        4970-2009 to calculate impacts and their effects on the trees.

        In relation to the majority of trees across the site, where till will be greater
        than 300mm the retention of trees becomes impossible. Assessment of the
        bulk earthworks plan indicates that fill will surround all trees, not just one side
        or part of their required TPZ. Generally fill over tree roots results in reduced
        aeration of the root zone, therefore leading to root death or dieback, and finally
        in most instances tree death.

        Although instances of fill near Melaleuca quinquenervia have been found to
        have a minimal effect on the tree species under the right situations (personal
        observations), given the overall age, poor health, and structural condition of
        the Melaleuca's on the site and the extensive nature and depth of filling across
        the site, the result would be tree death and or increased whole tree failures in
        the future.




Leaf and Limb Horticultural Consultancy©
Prepared by Samuel Cowie                                                     1 1 h of June 2009