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4. Mitigation Measures
Replacement planting is proposed to mitigate the loss of the 30 trees to be removed from within the main works area. In addition to replacement planting, works within the root zones of trees N1, T15- T19 and in the vicinity of T24 are proposed. Mitigation measures (as outlined in Section 4.2 below) will be implemented in order to protect trees N1, T15 –T19 and T24 which are to be retained.
Trees Requiring Removal
Trees G1, G2 and T1 –T19 will be removed during the main works. Replacement planting for G1, G2 and T1-T19 will be undertaken as part of the public realm reinstatement on completion of construction of the main works. Replacement planting will be addressed in a future Outline Plan for the reinstatement works, which will include an Urban Design DWP (UD DWP)
The method for removal of these trees will be informed by a qualified arborist in accordance with site observations, such as the proximity of surrounding buildings, tree size and overall condition. The methodologies used will include the following where relevant:
Staged removal whereby the outer limbs are removed first, followed by inner limbs and the main trunk. Depending on the location of utility lines, tree stumps shall either be dug out or ground in situ. Removed tree debris will either be mulched onsite or removed for mulching off-site, depending on which is more practicable.
All trees permanently removed as part of the works will need to be replaced to address adverse effects on private properties, amenity and local streetscape.
Replacement planting will be required for all trees that are required to be removed, as identified in Table 3-1 and Error! Reference source not found.. The location of replacement trees will be included in a replanting plan, which will be prepared as part of the UD DWP for the reinstatement of the CRL Mt Eden works. The UD DWP and accompanying replanting plan will consider the following in accordance with designation condition 55.3(c): o Replanting of removed trees at a ratio of at least 1:1; o Design for re-instatement of the area, including opportunities to replace removed trees with appropriate native species; o Input from the Auckland Council Parks Department (now Auckland Council Community Facilities) with regard to tree species / vegetation selection, tree pit construction and positioning of replacement trees; o An outline of the maintenance periods and responsibilities for care of the trees (i.e. maintenance is to be undertaken by the Requiring Authority for a period of five years for specimen trees and 3 years for all other landscape planting); and o Any consultation undertaken in relation to the replacement planting (refer to Section 5 of this TV DWP).
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Trees not Requiring Removal
Arboricultural Monitoring
Trees N1, T20-T21, and T24 will not be removed as part of the main works. Arboricultural monitoring will be undertaken to ensure these trees are adequately protected for the duration of the works. The following sections outline those measures specific to each retained tree.
The Works Arborist will oversee protection measures and be available (as required) to address any adhoc issues that may arise in relation to tree protection. In general, protection measures will include the following:
(a) Prior to any works commencing on the site in the vicinity of any of the retained trees, a meeting will be held at the site to discuss all issues pertaining to the protection of the trees and to gain a common understanding of the relevant recommendations. Present at the meeting will be; • The site foreman or project manager • The Works Arborist; • The Auckland Council Urban Forest Advisor; • Mt Eden Environmental and Sustainability Manager; and • Any other relevant personnel
(b)
(c)
(d)
(e)
(f)
(g)
Page 16 The Works Arborist will be present during any excavations through the dripline of any tree to be retained. Any scraping of soil within the dripline of trees shall be discussed with and approved by the Works Arborist prior to works commencing. The removal of hard surfaces within the dripline of trees proposed for retention is to be undertaken under the supervision of the Works Arborist. Care must be taken to not unnecessarily excavate within the dripline of any tree - with material to be removed by hand if necessary. No significant root severance exceeding best practice thresholds should be required. However, all root pruning must be assessed and approved by the Works Arborist. All roots larger than 60mm in diameter should be retained. All roots larger than 60mm in diameter must be retained unless their removal is deemed by the works arborist, so as to not adversely impact the tree. No heavy machinery or equipment or materials shall be stored or deposited within the TPZ of any retained tree within the site. If any materials do need to be temporarily deposited within the rootzone of any tree being retained, an impermeable, load bearing surface, appropriate for the task is to be laid down first. When machinery is to be used within the dripline of any retained tree, track movement must be kept to a minimum, with temporary load bearing surfaces installed where open ground is to be traversed prior to final surface preparation. At a minimum, geotextile cloth or metal is to be installed to prevent any soil compaction within the trees’ remaining root systems. New materials are to be preferably installed progressively from the previously metaled surface. . Any pruning of protected trees is to be undertaken under the supervision of the Works Arborist in accordance with modern arboricultural practice.
Mt Eden Main Works
(h)
(i)
(j) Protective fencing should be installed wherever practicable at the dripline edge of trees being retained. This fencing shall remain in place for the duration of the main works in order to best protect the subject trees. The fencing is to be a robust, self-supporting structure of at least of 1.8 metres. Temporary relocation of the fencing can be undertaken at the point where specific works are to be carried out within the TPZ of the subject trees - with the fencing to be re-erected following that specific activity. Any relocation is to be discussed with and approved by the works arborist prior to commencement Compliance with all aspects of construction relating to tree protection will be monitored by the Works Arborist - with the detail of each visit and communication being logged.
Additional Reporting
The Works Arborist shall also undertake regular Arboricultural Site Reviews (ASR) at a period of no less than once every two months works, for any works that are to taking place within 4 metres of the dripline of any retained tree(s). The ASR shall provide an opportunity to assess the health of retained trees, the tree protection measures, as well as providing general guidance to direct tree protection measures during the course of works.
The initial ASR should be undertaken at least 10 working days prior to the commencement of work within 10 metres of any tree which is to be retained. The initial ASR is to serve as the baseline from which any future perceived change in health or condition can be referenced against, with this document to be prepared by the Works Arborist. Following this, the Works Arborist will prepare a Tree Management Checklist to be issued to the Environmental and Sustainability Manager (ESM) and Mt Eden Site Environmental Adviser during the initial arboricultural site review to enable continuous monitoring of tree health in the intervals between each arboricultural site review.
The Tree Management Checklist should include (but may not be limited to):
Direction for assessing general tree health
Direction to identify deterioration of tree health
Contact details for the Works Arborist
The ESM / delegated advisor will undertake periodic monitoring of tree health as prescribed by the Tree Management Checklist at periods of no less than once every 14 days, and evidence of this monitoring should be provided to the ESM/delegated advisor for inclusion in the ASR. If the ESM/delegated advisor identifies evidence of declining tree health, the Works Arborist will be engaged to provide assistance in determining the cause of such deterioration and provide direction where appropriate.
Tree Specific Protective Measures –N1 (Notable Flame Tree)
Arboricultural monitoring, by the Works Arborist, will be required in order to ensure the protection of the Notable Flame tree for the duration of the works. As outlined in Section 2.1, construction of the Normanby Road grade separation bridge will include the regrading of Normanby Road and the realigning of the Boston Road roundabout. Works undertaken within the vicinity of, or within the protected root zone of Tree N1 (refer Figure 4-1), are to be approved by the Works Arborist, in accordance with Section 4.2.1 of this TV DWP.
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. Protective fencing will be erected under the supervision of the Works Arborist as near to the tree’s dripline edge as possible (where it overhangs the grassed berm area) for the duration of works (No fencing is necessary on the existing road surfaces). Any movement or relocation of fencing shall be discussed with the Works Arborist prior to implementation.
Figure 4-1: Notable Flame tree (N1)
Tree Specific Protection Measures –T20 & 21 (Ash trees)
These two trees stand on the corner of Lauder Road and Normanby Road (refer Figure 3-1 and Figure 4-3). It is anticipated that works will be required in close proximity to these trees as part of the abutment and retaining wall construction works.
A protective fence is to be erected between the construction works and the trees, with timber hoarding recommended to prevent stockpiling of construction materials. All works are to be undertaken in accordance with Section 4.2.1 of this TV DWP.
Figure 4-3: T20 & 21 as seen from the southwest Page 18 | Mt Eden Main Works
Tree T24 is standing on an elevated area of land within 14-22 Boston Road and overhanging Boston Road (refer Figure 3-1 and Figure 4-4). Works are proposed to construct retaining walls to the east of the tree. However, these works will be some distance from the Oak tree. All works are to be undertaken in accordance with Section 4.2.1 of this TV DWP and protective fencing will be erected near the tree’s dripline edge.
Figure 4-4: T24 as seen from the southwest
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