Arboricultural addendum To: Brendan Coghlan, Coastal Properties Ltd: coastalproperties@xtra.co.nz

From: Andrew Barrell, Consultant Arborist, Tree3 Ltd

Cc: Kate Madsen, Paua Planning: kate@pauaplanning.co.nz

Date: 9 July 2017

Re: 488 & 496C Hibiscus Coast Highway / development application

Protected trees / additional arboricultural comments

Introduction

1) I prepared an initial arboricultural report (dated 24 November 2015) for Coastal Properties (site owner) regarding a development proposal at 488 & 496C Hibiscus Coast Highway. At the time of writing that report the legacy Auckland Council (AC) District Plan rules were effective however those rules have now been superseded by the Unitary Plan.

2) AC have requested further information (by way of a section 92 Request For Further Information – s92) to clarify how adverse impacts are to be managed. A meeting occurred on site between the relevant project members and AC personnel on 30 June 2017. The AC arborist was present at this meeting and various tree issues were discussed in detail. The main area of concern was the management of the group of notable pohutukawa trees along the northern boundary of the site but other arboricultural issues were also discussed.

3) The aim of this addendum is to address the issues discussed during this meeting along with any other issues raised relating to the management of trees on and adjacent to this site.

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Areas of concern and responses 4) Concern #1

Concerns were raised about the extent of root damage to notable pohutukawa trees beyond the northern boundary arising from construction of buildings and basements. Response

a) The building is to be set back 8m from the boundary. It is anticipated that a one-metre overlap will be required to enable the works which puts the actual edge of the excavation at a point 7m from the boundary. I have been advised that the excavations along the northern boundary will include the use of sheet piling on the outer edge of the excavation to protect the actual excavation itself from collapse. This means that the outer edge does not need to be battered or extended for any other reason which in turn means the actual edge of the cut will be one metre out from the building edge and no further.

b) The eastern section of the group of notable pohutukawa trees stands approximately 5m

beyond the northern boundary and there is an access road in this gap servicing the businesses within the northern site. This translates as the actual edge of the excavation along this northern boundary being approximately 12m from the base of these eastern trees. Given the south-facing aspect of this side of the canopy of these trees (and the correspondingly-less vigorous canopy extension) and the presence of the service road immediately adjacent to the trunks of the easternmost pohutukawa trees (creating a less than ideal rooting environment which in turn will discourage extensive root growth), it is considered highly unlikely that there will be any roots of significance in the area of excavation i.e. where the sheet piling is to be installed.

c) The pohutukawa trees at the western end of the row are closer to the boundary, approximately 1-2m beyond the observed fence line. This places the trunks of the trees at a point approximately 8-10m from the anticipated location of sheet piling. As with the trees above, it is considered that there will be minimal root activity this far from the trunks on the south-facing aspect and therefore any root loss arising from installation of the sheet piling will be insignificant.

d) Any roots encountered during these initial excavations will be cut back to beyond the excavation face to leave clean-cut faces as opposed to shattered or torn edges. This reduces the stress on the subject tree. The area beyond the sheet piling will be fenced off to avoid any potentially root-damaging encroachments. Tree protection procedures have been included in section 4 of the original arboricultural report and these will be applied to manage any works around these trees.

5) Concern #2

AC expressed concerns that shading, leaf drop etc. would become problems that resulted in applications for extra trimming of the pohutukawa trees once the buildings were occupied and consequently requested information relating to how this issue could be addressed and/or managed in future to avoid unreasonable pruning applications. Response

a) This is considered to be a two-pronged issue. Firstly, the extent of trimming carried out prior to commencement of works will dictate how much clearance and space is left between the

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trees and the buildings. Secondly, the density of the tree canopies will further influence the percolation of light and perceptions of shading.

b) I believe that providing enough clearance prior to building construction will generate an adequate and reasonable sense of separation between the building and the trees. This will be achieved by trimming the southern extent of the canopy of the pohutukawa trees to a point at least 2m from the edge of the building. It is unlikely that trees of this age will respond with vigorous regenerative growth from this pruning on the southern aspect which in turn should ensure that ongoing maintenance pruning will only be required on perhaps a 3-5 year cycle, depending on the rate of regrowth. This maintenance pruning will focus on removing only new stems encroaching towards the building; the remainder of the canopy will not be interfering with the building and will not need to be trimmed. That said, there must be scope in any kind of canopy management system to allow for responses to extreme weather events, given the increasingly extreme and unpredictable weather patterns that are becoming commonplace. However, it is anticipated that adequate initial clearance will result in minimal ongoing pruning obligations.

c) In short, ensuring there is an initial clearance from the building of at least 2m lends itself to minimising any future remedial pruning requirements and also provides a reasonable compromise for both parties i.e. the trees and future residents. A policy of making potential residents aware of the obligation to avoid unnecessary pruning of these trees will mean that their expectations are managed to the extent that they accept the trees are there for the long haul and the observed level of separation will be maintained but not increased.

d) Pruning to achieve these clearances may entail making pruning cuts that do not strictly adhere to current arboricultural best practice. In particular there are limbs on the western pohutukawa trees that will require quite significant reduction pruning to provide the necessary clearances. If these cuts were to be made “properly” they would result in relatively large wounds on the main stems. I propose stub-cutting these stems some distance out from the main stem. This will give the limb a chance to regenerate new growth at the cut point. The worst-case scenario is that the limb does not survive; if this happens the cut will be some distance from the main stem which in turn means that there will not be the same potential for decay to spread into the main stem nor for it to be structurally compromised.

e) This replicates natural processes to a major degree and in this case I believe this is a sound and justifiable course of action. Ideally this work would be done prior to any other site works so that a mobile elevated working platform could be used to ensure the pruning is done as accurately as possible and with as little collateral damage (small limbs being damaged or broken off by a climber shimmying along limbs) as possible.

f) Figure 1 below illustrates this idea and also indicates the suggested location of non-target pruning cuts. The nikau stands beyond the sheet piling line and therefore can be retained. The yellow dotted line shows an approximation of 2m clearance from the building edge. The red lines on the upper limbs show approximate locations for stub cuts that will provide adequate clearance from the building edge whilst avoiding the need to make cuts on the main parent stems of the tree.

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Figure 1 – Canopy overhang of western pohutukawa and suggested stub-cutting points.

The yellow dotted line indicates and approximation of 2m clearance from the edge of the building. The red lines show suggested pruning points on larger limbs. Smaller limbs may be reduced back to appropriate pruning points as per arboricultural best practice techniques (target pruning). Note that these marks and lines are approximations only and serve to give an idea of what is proposed. Locating the stub cuts away from the building line will potentially allow for new growth to be accommodated in future pruning operations.

g) The extent of clearance pruning on the easternmost pohutukawa trees was of a much lesser nature and it is anticipated that the necessary limb removal would include some dead and nearly-dead limbs and some tip reduction on several other lateral limbs. The foliage on these trees was much less intrusive as they stand at least five metres further away from the site and consequently there is less woody material at the 2m clearance line.

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h) The canopy density of the trees appeared to be ideal i.e. it was not too dense (thus requiring no kind of thinning regime) but was also not too sparse (sparse canopy = poor vigour). Consequently I can see no justifiable reason to carry out any pruning on the canopy of these pohutukawa trees other than for general maintenance (removing dead or broken limbs etc.).

i) The western pohutukawa trees displayed dense infestations of ivy and other creepers within their canopies. These weeds would be removed as part of the proposal and their removal will serve both the interests of the trees (by removing massive competition for moisture and nutrients in the soil and reducing wind-loading during extreme weather events) and the interests of future residents in the proposed retirement village (by opening up the internal canopy and allowing much more light to percolate through). Removal of these weedy vine infestations will make a huge difference to the quality of the environment on the southern aspect of these trees and will provide significant ecological and amenity value improvements with no adverse impacts for the trees.

j) In summary: I. Adequate pruning clearances are recommended in the first instance to establish a

set clearance from the buildings which will be maintained, more or less, indefinitely.

II. This initial clearance pruning will require some unconventional pruning techniques however they are considered to be justifiable in this situation. All pruning work is to be carried out by professional and competent arboricultural contractors.

III. Maintenance of the pre-set clearance from the building will be achieved by a low-intensity pruning regime to trim new growth back to original pruning points, anticipated to be required on a 3-5 year cycle, or as dictated by the rate of new growth.

IV. This pruning regime will only require removal of new growth and no old growth limbs will require trimming.

V. There will be no requirement for additional canopy thinning / pruning other than the initial removal of weedy vine infestations and any safety works (e.g. broken or hung up limbs etc.).

6) Concern #3 Rose Cottage is to be moved 2m south from the esplanade reserve which places it within the canopy spread of the adjacent oak tree. This will require pile excavations in close proximity to the tree and there is potential for root zone damage. Response

a) Whilst there will be excavations within 1.5-2m of the trunk of the oak tree, it is anticipated that employing the standard arboricultural management procedures (see section 4.10 of the original arboricultural report) will ensure that any adverse impacts on the health or stability of the oak tree are insignificant.

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b) The same applies to any works in the vicinity of the pohutukawa trees and any other trees on the site which are to be retained.

7) Other issues

a) The fate of the Illawarra Flame tree, referenced as Tree 3 in the original arboricultural report, was discussed during the site visit. This tree showed extensive dieback and appeared to have declined in health since the previous site visit several months earlier. Given the relative rarity of the species and the potential for spectacular foliar displays it was decided to leave it alone to see if it would recover. It does not interfere with any works and may be left alone for another growing season. Based on how much live foliage remains, a remedial retrenchment regime would be advised whereby dead wood was removed leaving a framework of live branches that would hopefully allow the tree to regenerate into a viable specimen over time. If it dies it will be removed however it was deemed worthy of retention in the hope of survival.

b) A walnut tree located on the bank in the esplanade reserve was suggested for retention in

spite of being non-native to New Zealand. It stands on the edge of the bank and provides stabilisation for the bank edge as well as shady spots in the water which apparently are good for fish. Retention of this non-native tree will not have any significant adverse effect upon the integrity of the proposed replanting and will also provide a feature of interest for the area.

c) The well-being of all retained trees during any construction works is a priority and this will be achieved by following the recommendations in the original arboricultural report which essentially revolve around providing robust arboricultural management of all works around retained trees during the project.

Please feel free to contact me if you require further clarification of any of the above points.

Andrew Barrell

Director, Tree3 Ltd

9 July 2017

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