Supplementary Agenda of General Meeting

Deputy General Manager's Report No. IR16/13

Infrastructure and Recreation Division

Date of Meeting: 18/09/2013

22????? REQUEST TO REMOVE NATURE STRIP TREE AT 23-25 GRANTHAM CRESCENT, DANGAR ISLAND???

EXECUTIVE SUMMARY

?????????????? Council officers assessed a Eucalyptus pilularis (Blackbutt) tree located on the nature strip at 23?25 Grantham Crescent, Dangar Island as hazardous in 2011 and recommended removal of all the tree?s branches and foliage and retention of the hollow trunk of the tree for wildlife habitat.

?????????????? Consulting arborists identified options to preserve the tree, which included:

o???? reduction pruning to shorten limbs and reduce end weight and the establishment of a 12m exclusion zone.

o???? installation of a cable bracing system and establishment of a 6m exclusion zone, which is well within the drip zone (which is 8-12 metres from the trunk) of the tree.

?????????????? Council resolved to retain the tree.? Suitable planting and fencing was to be undertaken to divert pedestrians away from the tree and a review of the tree?s safety was to occur after 12 months.

?????????????? Planting under the canopy of the tree has not taken place due to safety considerations for workers. Instead pedestrian safety fencing was placed as recommended by consulting arborists.? This fencing has been removed on several occasions by unknown persons and subsequently reinstated by Council.?

?????????????? The condition of the tree does not appear to have altered during the last 12 months.? There have been no incidents reported to Council regarding further live limb loss from the tree, although further limb loss is considered inevitable. Council has been contacted by concerned nearby residents about the tree.

?????????????? The tree is a very large mature, remnant Blackbutt that forms part of a group of trees that is listed under Schedule D (Heritage Items) of the Hornsby Shire Local Environmental Plan (HSLEP) 1994.

?????????????? This Report recommends the effective removal of all branches and foliage of the remnant nature strip Eucalyptus pilularis (Blackbutt) tree located at 23?25 Grantham Crescent, Dangar Island, retaining the trunk for wildlife habitat and replacing it with one locally indigenous tree of the same species.

RECOMMENDATION

THAT Council:

1.???????? Approve the removal of all branches and foliage of the remnant Eucalyptus pilularis (Blackbutt) nature strip tree located at 23?25 Grantham Crescent, Dangar Island, retaining the trunk for wildlife habitat.

2.???????? Plant a replacement tree of the same species in Grantham Crescent, Dangar Island.

PURPOSE

The purpose of this Report is to provide Council with the information required to further consider whether to retain or remove one Blackbutt tree which contains nesting hollows and has a history of large diameter limb loss.?

BACKGROUND

At the 21 September 2011 Ordinary Meeting, Council considered Executive Manager?s Report No. EN43/11 and resolved:

?THAT:

1.???????? The Eucalyptus pilularis (Blackbutt) on the nature strip at 23-25 Grantham Crescent Dangar Island, the subject of Executive Manager?s Report No. EN43/11, be retained as is.

2.???????? Suitable planting, in consultation with the local Bushcare Group, be undertaken around the base of the tree to assist in redirecting the path and diverting pedestrians.

3.???????? A review of the tree?s safety and effectiveness of the planting in the exclusion zone be undertaken by the Executive Manager, Environment within 12 months.?

Nearby residents have raised concerns about the tree and one resident has formally sought a review of Council?s decision to retain the nature strip tree.

The initial report presented for Council?s consideration in 2011 (Attachment 1) recommended the effective removal of one locally indigenous, remnant Blackbutt tree that forms part of a group of trees that is listed under Schedule D (Heritage Items) of the Hornsby Shire Local Environmental Plan (HSLEP) 1994.? Due to a history of large branch drops onto Grantham Crescent, Council officers assessed the tree as hazardous and recommended removal of all the tree?s branches and foliage to retain the hollow barrel of the tree for habitat together with appropriate replacement planting.

Some members of the community at the time expressed opposition to the proposed tree removal.

Independent arborist advice was sought on the matter and alternative responses and the attendant levels of risk were discussed in their reports (Attachments 2 and 3).

Both independent arborists recommended the retention of the tree, with measures to reduce risk, such as fencing, path redirection and cable-bracing.? These measures would constrain public access in Grantham Crescent.

DISCUSSION

Tree Details

Species:????????????? Eucalyptus pilularis

Common Name:??? Blackbutt

Height:???????????????? 38 metres

Age:??????????????????? Over mature

Photographs of the tree taken in 2011 have been included for Council?s information (Attachment 4).

Clause 18(2) of the HSLEP 1994 permits the alteration of heritage items without development consent if the Council is of the opinion that the proposed development would not adversely affect the heritage significance of the heritage item.? Accordingly, Council?s Planning Division assessed the impact on the heritage item (some thirty trees) and has determined that development consent is not required for the proposed work to remove the subject tree under Clause 76(1) of the Environmental Planning and Assessment Act 1979.

All parties agree that there have been many failures of large diameter scaffold limbs (large branches that form the framework of the tree) over the years and that further failures are likely if action is not taken.? The community is divided regarding the removal of the tree.? As a demonstration of due diligence, advice from two expert consulting arborists was sought.? Reports were obtained from The Sugar Factory (TSF) and from The Arborists Network (TAN) on the tree and these arborists were each asked to provide a recommendation.? Both independent reports recommended fencing and either crown modification or cable and bracing for the tree and ongoing re-assessment.

Ongoing testing for the soundness of hollow limbs was recommended, however there is no standard measurement for concluding whether the limbs are sound or not.? The measures recommended by the consultant arborists were considered impractical and costly, and are not supported. Instead, the report recommends the removal of all branches and foliage of the tree, retaining the trunk for wildlife habitat and replacing it with new trees.

Concerns

The major issue of concern is that any future branch failures may cause extensive damage to property or injury to persons.? There are no quantitative parameters for the assessment of failure potential of limbs due to branch hollowness; therefore it is not possible to assess the soundness and safety of the tree?s limbs.

The tree fencing recommended by the consulting arborists has been removed on several occasions by unknown persons and subsequently reinstated by Council.? Currently the fencing is not placed at the recommended distance due to its repeated removal when placed further out. Replacement plantings under the canopy of the tree have not taken place due to safety considerations.

Options Available

Three options have been identified as being available to Council and are summarised below for Council?s information.? A more detailed discussion about these options is contained in the initial report to Council (Attachment 1).

Option A ? Leave the tree as is

The Arborists Network recommendation to retain the tree ?as is?:

?????????????? Reducing the risk in the ?target? or branch drop zone, by redirecting the path and diverting pedestrians via the use understorey planting or fences.

?????????????? Reducing the probability of failure onto the path by installing a cable bracing system.

Option B ? Retain the tree and modify the crown

The Sugar Factory recommends ?retain the tree and modify the crown?:

?????????????? Reduction and remedial pruning to shorten limbs and reduce end weight, combined with testing of wood soundness on main scaffold branches and trunk.

?????????????? Exclusion fencing installed at 12m from the trunk, which would impede use of the public road and some private properties.

?????????????? Annual inspections.

Option C ? Remove the tree

Council?s arborists recommend that the canopy of the tree be removed and treated to prevent re-growth, so that only a 12m - 16m tall dead trunk remains for habitat.? This option will not require fencing.

BUDGET

There are budgetary implications arising from a decision to adopt one of the three options listed above.

Option A:

The cost of cable and bracing could be approximately $15,000.? There may be additional maintenance cost to the cable and bracing system, particularly when branches fail.? No estimate of the maintenance cost can be made. Added to this would be $6,670 for the cost of annual resistograph testing for the remainder of the tree?s life.?

Option B:

The cost for resistograph testing and a report on the Blackbutt is $6,670 (including GST).? This would be an annual cost for the remaining life of the tree.

Option C:

The estimated cost for the removal of the tree is $5,000.

The above costs do not take in to account the cost of maintaining the security fence and any diversion of Grantham Crescent.

POLICY

The recommendation of the report is consistent with Council?s Tree Preservation Order.

CONCLUSION

The condition of the tree does not appear to have altered during the last 12 months.? The measures recommended by the consultant arborists from their reports commissioned in 2011 are considered impractical and costly, and are not supported.? Consequently this Report identifies Option C as the recommended course of action.

RESPONSIBLE OFFICER

The officer responsible for the preparation of this Report is the Manager - Parks and Recreation ? Peter Kemp - who can be contacted on 9847 6792.

Robert Stephens

Deputy General Manager

Infrastructure and Recreation Division

Attachments:

1.View	Attachment 1 - Copy of Report to Council EN43/11 - Request to Remove Tree at 23 - 25 Grantham Crescent Dangar Island
2.View	Attachment 2 - Aborist Report - The Sugar Factory - 23 - 25 Grantham Crescent Dangar Island
3.View	Attachment 3 - Aborist Report - The Arborist Network - 23 -25 Grantham Crescent Dangar Island
4.View	Attachment 4 - Photo - July 2011 - 23 -25 Grantham Crescent Dangar Island	Included under separate cover
5.View	Attachment 5 - Aerial Photo - Tree - 23 - 25 Grantham Crescent Dangar Island	Included under separate cover

File Reference:?????????? F2009/00081-14

Document Number:???? D02183150