Consultancy / Reports / Site Monitoring / Tree Surveying / Tree Safety Inspections / Design Reviews. Memorandum

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1 Consultancy / Reports / Site Monitoring / Tree Surveying / Tree Safety Inspections / Design Reviews Memorandum To: Benedict Free Arboricultural and Landscape Advisor, Auckland Council From: Sean McBride Director, Treesafe Consultancy Ltd Date: 19 April 2016 Subject: 2 Oxford Terrace, Devonport Re-inspection of Gum trees and TRAQ assessment. Dear Benedict Treesafe Consultancy Limited has been retained by Auckland Council to undertake a further ground based visual inspection of two Gum trees that are located outside of 2 Oxford Terrace, Devonport, and to undertake a TRAQ (Risk) assessment. The request for our services are a result of concerns raised by an adjacent property owner. An arboricultural report on the two trees was prepared for a local resident by Gordon Ikin of The Specimen Tree Company (dated 15 December 2015). I have been asked to peer review this assessment. I initially visited the site on the 28 th of March 2015 where I undertook a brief visual tree inspection of the trees from ground level. At this time the trees were assessed to be in good health with no obvious signs of structural defects that would warrant immediate remedial work. The removal of deadwood from within the canopy had been carried out prior to this visit and it was noted that a number of medium sized pieces of deadwood were still present. Further deadwood was recommended. I revisited the site on the 23 rd of February 2016 where a further ground based inspection of the two trees were carried out. During this site visit I also undertook a Tree Risk Assessment (TRAQ). My completed tree risk assessment form is attached to this memorandum. Based on my visual inspection of the two trees from ground level, a peer review of The Specimen Tree Company arboricultural assessment and tree risk assessment, my comments are outlined in the below assessment. Arboricultural Assessment The two subject trees are Gum trees (Eucalyptus sp) growing outside of 2 Oxford Terrace. At the time of writing this memo, I was unable to confirm the species of Eucalyptus. Standing at some 15m and 16m in height the overall health of the trees are good. No obvious decline has occurred between the 12 months of my two inspections. It was noted that a couple of small snapped branches were hung up in the canopy of the trees at the time of my inspection. It is likely these small failures occurred during adverse weather conditions.

2 The Specimen Tree Company Report recommended removal of the two trees based on the following conclusions: The size of the tree and especially the size they will become as they mature potentially several times larger than the size that they currently are. Their very close proximity to the adjacent residential properties The damage that they have caused and will continue to cause to the adjacent infrastructure primarily underground services, the footpath, kerb and channel, and vehicle crossings. The integrity of the branch union on the eastern tree where it divides it 7m above ground level and the weight loading from the stems that are growing to the north of this union that extend out over the property The potential for Sudden Limb Drop occurring. The on-going pruning that will be required to keep the trees clear from the adjacent electrical lines and keep them in spec for this clearance. I provide my comments in relation to these aspects below: The size of the trees and potential for future growth. The potential size the trees can develop into is dependent of the species of Eucalyptus and the growing environment that are establishing in. The species of Eucalyptus is yet to be verified so the potential for them to grow 1.5 times their current height, or times their current width is uncertain. It is also important to consider the environment the trees are developing in as to whether they can grow to their full potential. As the rooting environment is restricted by the presence of a road, footpath and other impermeable surface areas, it is unlikely that the trees have the potential to reach full stature of whatever species of Eucalyptus they may be. Their proximity to the adjacent residential properties. Where trees are in close proximity to properties or structures, consideration of potential targets (such as the dwelling being within the canopy spread of one of the trees), the structural integrity of the tree, any potential defects, and the severity of damage should failure occurs all needs to be considered. Just because trees are close to residential properties does not mean they all should be removed. In order to calculate any potential risk there may be to the dwelling or occupants of the property, a Tree Risk Assessment has been carried out using TRAQ. I am qualified through the International Society of Arboriculture to use this system. The risk assessment and results are describes later in the memorandum. Damage to infrastructure There is little doubt that trees have potential, and do, damage infrastructure such as footpath, kerbs, roads and other structures. Depending on the health and structure of the trees, it is also common to look for suitable designs when undertaking the repairs should the trees warrant such measures. In my view, given that they are some of the tallest growing trees in the immediate vicinity, in good health and with no obvious structural defects that would warrant immediate remedial works, these trees would warrant various design options being explored. In the absence not knowing these potential designs (or potential lack of), it would not be appropriate to prematurely remove them. With regards to damage to underground pipes, and in particular wastewater and stormwater, it is most common for existing faults in the pipework to exist, and the subsequent moisture leakage, for trees to search and exploit. Once within the pipework, a matting of fibrous root activity generally establishes. From my experience, in most cases there is prior fault with the pipework that tree roots will exploit.

3 Integrity of the branch union The risk associated with any potential branch failure is outlined in the below sections of this memorandum (TRAQ). As a conservative approach, I have categorised the likelihood of failure being possible. Sudden Branch Drop I agree that Sudden (or Summer) Branch Drop (SBD) is associated with Eucalyptus (and other) tree species and that it is currently unpredictable. Seeming healthy trees free of defects can fail with no obvious prior signs suggesting it were to occur. It is stated in The Specimen Tree Companies report that SBD is not common. I also agree with this statement and would further describe it as an event that is not frequent. The removal of otherwise healthy trees solely based on an infrequent occurrence, in my view is not sufficient justification for the removal of the trees. Again to err on the side of caution, I can calculated a risk rating for SBD. Ongoing pruning for line clearance Pruning to clear the powerlines appears to have been previous undertaken, where the canopy and main scaffold branches of the tree are now above the lines. Future conflict may occur when either new foliage establishes along the trunk (unlikely in my view), or through future girth development and expansion of scaffold branches. As mentioned previously above, the extent of future growth and development of the tree is dependent on the species of Eucalyptus, and no assumptions can be made for if future conflict may arise. In any event any potential conflict is likely to be a number of decades away, and by that time it is possible the powerline may be underground. TRAQ Overall the risk rating for a branch failure and damage to the nearby dwelling, powerlines, people using the footpath or cars parked beneath has been calculated to be Low. It is worthy at this point to briefly describe the rationale behind a number of likelihood of events occurring. As mentioned above, and from a conservative perspective, the main concerns with the tree are branch failure through either SBD or other branch snapping events. The likelihood of branch failure has been assessed as Possible (i.e. failure could occur, but is unlikely during normal weather conditions within a 3 year time period). The likelihood of a large branch hitting either a house, powerlines or parks car has been assessed to be High (i.e. the failed branch will most likely impact the target.). For pedestrians on the footpath, this has been assessed to be Medium (although more likely to be low). For the house, powerlines and parked cars the likelihood of failure and impact is calculated to be Somewhat likely, whereas people on the footpath is Unlikely. Reviewing the consequence of branch failure, it has been assessed the house, powerlines and parked cars as being Minor; that being defined as low to moderate property damage or small disruptions to traffic or a communication utility. Generally power is restored quickly, and I am yet to personally view significant damage to dwelling through branch failure (rather than whole tree failure which is not the main concern in this case). With a likelihood of failure and impact being somewhat likely, and consequences being minor, the overall risk rating is Low.

4 With respect to people, the consequences are severe however as it is unlikely, the overall risk rating is also calculated to be Low. Recommendation Given the above, it is my recommendation only the removal of major dead branches and small hang up branches is carried out. Please do not hesitate to call me should you require more specific details Yours sincerely Sean McBride Director Treesafe Consultancy Limited

5 Client Date Time Address/Tree location Tree no. Sheet of Tree species dbh Height Crown spread dia. Assessor(s) Time frame Tools used Target number Unbalanced crown LCR % Dead twigs/branches % overall Max. dia. Broken/Hangers Number Max. dia. Over-extended branches Pruning history Crown cleaned Thinned Raised Reduced Topped Lion-tailed Flush cuts Other Trunk Dead/Missing bark Abnormal bark texture/color Codominant stems Included bark Cracks Sapwood damage/decay Cankers/Galls/Burls Sap ooze Lightning damage Heartwood decay Conks/Mushrooms Cavity/Nest hole % circ. Depth Poor taper Lean Corrected? Response growth Main concern(s) Target description Target Assessment History of failures Topography Flat Slope % Aspect Site changes None Grade change Site clearing Changed soil hydrology Root cuts Describe Soil conditions Limited volume Saturated Shallow Compacted Pavement over roots % Describe Prevailing wind direction Common weather Strong winds Ice Snow Heavy rain Describe Tree Health and Species Profile Vigor Low Normal High Foliage None (seasonal) None (dead) Normal % Chlorotic % Necrotic % Pests Abiotic Species failure profile Branches Trunk Roots Describe Load Factors Wind exposure Protected Partial Full Wind funneling Relative crown size Small Medium Large Crown density Sparse Normal Dense Interior branches Few Normal Dense Vines/Mistletoe/Moss Recent or planned change in load factors Main concern(s) Basic Tree Risk Assessment Form Site Factors Tree Defects and Conditions Affecting the Likelihood of Failure Crown and Branches Cracks Codominant Weak attachments Previous branch failures Lightning damage Included bark Cavity/Nest hole % circ. Similar branches present Dead/Missing bark Cankers/Galls/Burls Sapwood damage/decay Conks Response growth Load on defect N/A Minor Moderate Significant Likelihood of failure Improbable Possible Probable Imminent Heartwood decay Roots and Root Collar Collar buried/not visible Depth Stem girdling Dead Decay Conks/Mushrooms Ooze Cracks Root plate lifting Response growth Main concern(s) Target within drip line Target zone Target within 1x Ht. Cavity % circ. Target within 1.5 x Ht. Cut/Damaged roots Distance from trunk Soil weakness Occupancy rate 1 rare 2 occasional 3 frequent 4 constant Practical to move target? Restriction practical? Load on defect N/A Minor Moderate Significant Likelihood of failure Improbable Possible Probable Imminent Load on defect N/A Minor Moderate Significant Likelihood of failure Improbable Possible Probable Imminent Page 1 of 2

6 Risk Categorization Condition number Tree part Conditions of concern Part size Fall distance Target number Target protection Improbable Failure Possible Probable Imminent Likelihood Impact Very low Low Medium High Failure & Impact (from Matrix 1) Unlikely Somewhat Likely Very likely Consequences Negligible Minor Significant Severe Risk rating of part (from Matrix 2) Matrix 1. Likelihood matrix. Likelihood Likelihood of Impacting Target of Failure Very low Low Medium High Imminent Unlikely Somewhat likely Likely Very likely Probable Unlikely Unlikely Somewhat likely Likely Possible Unlikely Unlikely Unlikely Somewhat likely Improbable Unlikely Unlikely Unlikely Unlikely Matrix 2. Risk rating matrix. Likelihood of Failure & Impact Consequences of Failure Negligible Minor Significant Severe Very likely Low Moderate High Extreme Likely Low Moderate High High Somewhat likely Low Low Moderate Moderate Unlikely Low Low Low Low North Notes, explanations, descriptions Mitigation options Residual risk Residual risk Residual risk Residual risk Overall tree risk rating Low Moderate High Extreme Work priority Overall residual risk Low Moderate High Extreme Recommended inspection interval Data Final Preliminary Advanced assessment needed No Yes-Type/Reason Inspection limitations None Visibility Access Vines Root collar buried Describe This datasheet was produced by the International Society of Arboriculture (ISA) and is intended for use by Tree Risk Assessment Qualified (TRAQ) arborists 2013 Page 2 of 2