51 Chevening Road Arb report - planning.org.uk

Frank Parsons Arboricultural ist Parsons Tree Care Limited 2 Accommodation Road London NW11 8ED 07791 652 889 f [email protected]

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Arboricultural Report Client: Karen Granger

Site: 51 Chevening Road London NW6 6DB Survey undertaken: Trees in relation to design, demolition and construction –

Recommendations. Author: Frank Parsons 15th September 2021

RFS certificate in Arboriculture AA Technicians certificate in Arboriculture (Level 4 Diploma in Arboriculture)


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Appendices 1. Background

2. Clients Brief

3. Scope

4. Site Observations

5. Proposed Development

6. Plans

i. Tree Survey ii. Survey Map iii. Tree Constraints Plan iv. Tree Protection Plan

7. Tree Protection Methodology

i. Construction Exclusion Zones ii. Foundation guidance iii. Utility installation guidance

8. Arboricultural Implications Assessment

9. Site observations (photos)

10. Arboricultural Method Statement

11. Conclusion

12. References


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1. Background: This report is to be read in conjunction to the tree survey attached, which has been undertaken to identify any trees within or affected by the proposed development at the site address that should be removed or retained and therefore protected during the proposed development. This report will outline tree categorization methodology with reference to BS 5837:2012. The proposed site is within a conservation area. The local authority is the London Borough of Brent. 2. Clients Brief:

• To undertake a tree survey within the rear gardens of affected properties. To scale plan supplied by Studio Mcleod.

• To provide an Arboricultural report identifying the trees to be retained, removed or

worked on within the proposed development and outline and evaluate the constraints posed by the trees retained on site via:

• Root Protection Area (RPA) – Layout design tool indicating the area surrounding a tree

that contains sufficient rooting volume to ensure the survival of a tree, shown in plan form.

• Construction Exclusion Zone – Area based on the RPA, identified by an arboriculturalist, to be protected during development, including demolition and construction work, by the use of barriers and or ground protection, fit for purpose to ensure the successful long term retention of a tree.

• Tree Protection Plan (TPP) – Scale drawing prepared by an arboriculturalist showing the finalized layout proposals, tree retention and tree landscape protection measures detailed within the arboricultural method statement (AMS), shown in plan form.

• Arboricultural Implications Assessment – Study undertaken by an arboriculturalist, to identify, evaluate and possibly mitigate the extent of direct and indirect impacts on existing trees that may arise as a result of the implementation of any site layout proposal.

• Arboricultural method statement (AMS) – Methodology for the implementation of any aspect of development that has the potential to result in loss or damage to a tree. N.B. The AMS is likely to include details of an on site tree protection monitoring regime, construction traffic management plan in relation to trees and a tree pruning schedule.


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3. Scope: The survey has been conducted in accordance with BS 5837:2012 Trees in relation to design, demolition and construction – Recommendations. 4. Site Observations: 51 Chevening Road is a terraced property in the Queens Park conservation area of the London borough of Brent council. The front garden consists of patio with a car parking space and a planting bed with no trees. The rear garden is north west facing, approximately 5m in width and 35m in length. Decking surrounds the rear of property and side return. The remainder and majority of rear garden consists of lawn with planting beds either side. Small fruit trees have been planted throughout the lawn areas as well as a hedge to screen off the garden shed at the rear end of the garden. A mature Ash tree grows on the rear boundary in a raised bed, which is most likely the same age as the house. The tree has been significantly reduced within the last two years. A railway line runs behind the rear boundary of the garden. The boundary fences are made of timber and are 4ft high either side. The soil profile is London clay. 5. The Proposed Development: The proposed project is a complete refurbishment of ground floor, rear garden extension to align with neighbour incorporating the side return and an installation of a garden room to the rear of garden. Please refer to the architect’s plans and drawings for detailed illustrations and descriptions. (Drawing reference number 264-PRE-01) 6. (i) Tree Survey Attached as a separate pdf documents: Reference - FP/TS/263 (ii) Survey Map - attached as a separate pdf document identifying tree numbers and BS Tree Categories: Reference – TMS 51 Chevening Road.

Below: Table 1 – Cascade chart for tree quality assessment


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(iii) Tree Constraints Plan: Attached as a separate pdf drawing: Reference TCP 51 Chevening Road (iv) Tree Protection Plan: Attached as a separate pdf drawing: Reference TPP 3 Chevening Road 7. (i) Construction Exclusion zones (CEZ’s): _Guidance only Barriers and/or ground protection should protect trees that are being retained on site before any materials or machinery are brought onto the site, and before any demolition, development or stripping of soil commences. Where all activity can be excluded from the RPA, vertical barriers may be erected to create a construction exclusion zone. However in the case of this site the garden boundary fences will act as construction exclusion fences confining all construction activity to no.51. Barriers will not be applicable in excluding construction activity taking place around the retained tree due to the proximity of proposed installation to the tree. The mixing and storage of materials is prohibited within the construction exclusion zones, contractors and machinery are also prohibited within CEZ’s to mitigate soil compaction. This should be communicated via the project manger at commencement of each stage of the development.

Fig.1 BS 5837:2012:

Example of typical tree protection fencing used

to demarcate the calculated construction

exclusion zone.


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(ii) Recommendations to mitigate or eliminate damage to tree roots within RPA’s -

To mitigate severance of roots for foundation construction specialist methods should be used: Screw piles, with site investigation used to determine their optimal location whilst avoiding damage to roots important for the stability of the tree, by means of hand tools or compressed air soil displacement, to a minimum depth of 1.5m. Beams, laid at or above ground level, and cantilevered as necessary to avoid tree roots identified by site investigation. Designs for foundations that would minimize adverse impact on trees should include particular attention to existing levels, proposed finished levels and cross-sectional details. In order to arrive at a suitable solution, site-specific and specialist advice regarding foundation design should be sought from the project architect, developer and an engineer.

(iii) Appropriate measures to eliminate or mitigate severance of roots for construction of a utility service:

Mechanical trenching for the installation of underground apparatus and drainage severs any roots present and can change the local soil hydrology in a way that adversely affects the health of the tree. For this reason, particular care should be taken in the routing and methods of installation of all underground apparatus. Wherever possible, apparatus should be routed outside RPAs. Where this is not possible, it is preferable to keep apparatus together in common ducts. Inspection chambers should be sited outside the RPA. Where underground apparatus is to pass within the RPA, detailed plans showing the proposed routing should be drawn up in conjunction with myself. Trenchless insertion methods should be used with entry and retrieval pits being sited outside the RPA. Provided that roots can be retained and protected, excavation using hand-held tools might be acceptable for shallow service runs where applicable.

8. Arboricultural Implications Assessment:

The proposed extension and refurbishment works to the main property would not affect any trees in the vicinity. There are no street trees in the immediate area and no trees in the rear garden, which are close enough to the rear elevation of the property to be impacted by demolition or construction. The proposed development in the rear garden is a small-scale garden room with limited access considerations. No construction vehicles or heavy plant machinery will be necessary or permitted on site due to the limitations of the site access being through the property. Therefore soil compaction is unlikely to be a constraint with regards to the rooting areas of retained trees. It was observed that a number of small trees have been planted in the rear garden in the last 18 months, the stem diameter of which do not qualify to be included in this survey, however these trees are all of arboricultural merit and you have stipulated that the contractor should ensure no damage occurs to the garden and newly planted trees during the proposed development. (i) The footprint of the garden studio room in its proposed position is within the root protection area (RPA) of T1 – Common Ash. The tree has a significant cavity within the stem base in between


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buttress flares and the canopy has been recently reduced to contain the spread and reduce wind loading on the structure to mitigate failure. Due to the proximity of tree to proposed installation I would recommend no excavation in the area as root disturbance and severance would be highly likely. The mixing of materials and contaminants would also attribute to root desiccation therefore pouring of concrete should not occur within the RPA of T1. Soil compaction can lead to anaerobic conditions for root growth therefore any installation should be supported (100mm) above soil level to allow for water, nutrient uptake and airflow within the rooting area of T1. (ii) The hard standing currently used for the existing shed should be removed to make way for the installation of screw piles to support the floor base of the garden room. These screw piles are relatively non invasive, normally to a depth of 1.8m can be positioned in areas away from primary structural roots with arboricultural supervision. Adopting this method of foundation base would mitigate any detrimental impacts to the physiological or structural condition of T1.

9. Site Observations

Photo 1: Illustrates proximity of T1 to existing garden shed. The Common Ash grows in a raised bed supported by railway sleepers.


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Photo 2: Taken facing northwest towards the mature Ash. Heavy pruning has resulted in the response of mass regrowth from pruning points to compensate for the loss of canopy. This is a normal response for this species of tree. Railway runs behind rear garden. Small cherry to be retained (DBH under 75mm at 1.5m above ground level).


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Photo 3: Depicts extent of cavity in stem base of T1. Tree has a BS category of C (refer to table on page 5) Reaction growth on buttress flares support tree stem. Cyclical crown reduction will maintain a contained spread and manage the tree in its location in relation to its structural condition. Photo 4: Tree stem of T1 bifurcates at 3m from ground level to form 2 scaffold limbs that have been heavily reduced. The Ash tree is most likely the same age as the property (circa 100years). There was no sign of Ash dieback present in canopy.


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Photo 5: View towards the rear elevation of property illustrating the well-maintained landscaped gardens. Newly planted trees in lawn to be retained and protected during the proposed development. Area adjacent to existing decking would offer space for storage of materials during construction of the garden room. Photo 6: illustrates the closest street tree to property (2 houses away from no.51) The proposed refurbishment of house would not impact the rooting area of this tree.


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10. Arboricultural Method Statement:

To ensure the health and existing vitality of the trees that grow in and around the proposed site, the AMS should be used in conjunction with the tree protection plan attached to this report. (TPP 51 Chevening Road) See below for trees that require protection prior to demolition and construction. T1 – Common Ash: RPA impacted by installation of proposed garden room. Approximately 25% of the rooting area of the tree would be covered by the structure. No excavation permitted. Adopt use of 1.8m screw piles to support floor base. No mixing of materials within RPA. Ground protection matting conforming to BS5837:2012 to be laid from raised bed at rear of garden extending 8m towards house to mitigate soil compaction from contractor footfall. (i) Pruning: No canopy pruning is required for the proposed installation. Root pruning within RPA of T1 to install screw piles may be required should the project gain planning which a qualified and insured arboriculturalist should undertake. (ii) Installation of services and utility runs: At this stage it is not clear where the service runs and inspection chambers will be installed. The tree protection plan sets out a proposed service run which would minimize the impact of the rooting areas of the trees in the rear. All services running through the RPA of T1 must be installed by hand dig only with arboricultural supervision. (iii) Construction exclusion zones: The boundary fence lines will act as construction exclusion zones and it would not be necessary to install tree protection fencing set out in section 7(i). (iv) Site access: The site access denotes the scale of machinery permitted onto site. All materials and machinery have to be brought through the interior of property therefore no heavy plant would be used on this project. (v) CTMP – construction traffic management plan with regards to deliveries. It would be advisable to suspend parking bays outside the front of property for the delivery of

materials. The front garden hard standing may offer some space to store materials. There are no street trees outside the front of property that require protection.

11. Conclusion

The proposed garden room adjacent to the rear boundary of 51 Chevening Road is a small-scale

project enhancing what is currently storage space at the end of the rear garden. The garden room would nestle underneath the canopy of the mature Ash tree. There are no major constraints on this project due to the screw pile foundation design eliminating the need for excavation in the rooting area of T1. I do not foresee the project causing a detrimental effect on the physiological or


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structural health of the Ash tree surveyed in this report. The refurbishment and extension on the rear elevation of property is at distance far enough away not to impact any surrounding trees in the vicinity.

Construction activity would be restricted to light machinery with no heavy plant permitted on site

due its situation with limited access. The boundary line fences on the east and west boundaries will act as a construction exclusion zone, confining all construction activity to the rear garden of no.51 therefore other neighbouring trees would not be affected by the proposed installation.

Storage and mixing of materials should take place within the designated area highlighted in the tree

protection plan (TPP 51 Chevening Road) to minimise work carried out underneath T1 and other newly planted trees that you have highlighted for protection.

Cellular ground protection matting will mitigate soil compaction in the area in front of the proposed

garden room during the project without reducing soil water absorption capacity. A qualified arboriculturalist should approve installation of ground protection.

Excavation should be kept to a minimum to investigate the areas to install the screw piles to

support the floor base. Roots exceeding 50mm in diameter should not be removed without prior consultation from a qualified arboriculturalist. For installation of service runs below ground level, excavation should be hand dig only.

The Tree Protection Plan demonstrates measures to protect trees on site and provided this report is

communicated to the contractor prior to the project commencing I do not foresee the proposed garden room build causing adverse effects on the mature Ash tree surveyed within this report. Tree work undertaken should be in accordance with British Standards 3998:2010. I would oversee the project prior to works commencing, during and after the proposed development for continuity should the client gain planning.

This report is to be submitted in conjunction with Tree Survey – FP/TS/263, Site Plans – TMS 51 Chevening Road, TCP 51 Chevening Road, and TPP 51 Chevening Road.

12. References:

• BS 5837:2012 – Trees in relation to design, demolition and construction – Recommendations

• Original scale site survey supplied by Studio Mcleod.

51 Chevening Road Arb report - planning.org.uk

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