Arboricultural Ltd Method Statement Norfolk

Arboricultural Method Statement

MAN/THTAC/AMS/01

Client: Mansell Construction Ltd

Site: Thetford Academy,

Croxton Road, Thetford, Norfolk

Author: T. Sorensen Date: 10.11.2011

Revision History:

Ravencroft Arboricultural Services 6 Reepham Road Foulsham, Norfolk NR20 5SL

Tel/Fax: 01362 684291

Email: [email protected]

Ravencroft Arboricultural Services

Arboricultural Method Statement – Valley Primary School Norwich NPS/VALPS/AMS/04

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1 Introduction

1.1 Instruction and brief ................................................................................................................. 3

1.2 Limitations ................................................................................................................................ 3

2 Implementation phases

2.1 PHASE 1 – Pre commencement ............................................................................................. 4

2.2 PHASE 2 – Root investigations ............................................................................................... 5

2.3 PHASE 3 - Implementation tree works .................................................................................... 6

2.4 PHASE 4 - Implementation of tree protection measures ......................................................... 7

2.5 PHASE 5 – Demolition and Construction ................................................................................ 9

2.6 PHASE 6 - Completion .......................................................................................................... 10

3 Appendices (not paginated)

3.1 Appendix 1 - Tree Survey Schedule

3.2 Appendix 2 – Tree Protection Plan

Author: Tony Sorensen BSc (Hons) Arb. M.Arbor. A

Signed:

Date: 10.11.2011

Contents



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1 Introduction

1.1 Instruction and brief

1.1.1 Ravencroft Arboricultural Services have been instructed by Bidwells LLP

acting on behalf of Mansells Ltd to provide an arboricultural method

statement for the demolition of existing buildings and the construction of a

new academy building, associated access roads, pedestrian walkways,

playing fields and car parking at Thetford Academy, Croxton Road, Thetford.

1.1.2 The method statement will be undertaken in accordance with the

expectations of British Standard 5837:2005 ‘Trees in Relation to

Construction - Recommendations’ (unless superseded by more recent

research) and is based upon the information presented within the associated

Arboricultural Implications Assessment (MAN/THTAC/AIA/01A).

1.2 Limitations

1.2.1 Ravencroft Arboricultural Services are not responsible for the related

accuracy of any information received by a third party for the purpose of the

tree survey or development proposals. No checking of independent third

party data will therefore be undertaken.

1.2.2 This methodology must be read and integrated into the appropriate

development phases, which falls outside our field of expertise.

1 Introduction



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1.2.3 If any part of this statement is unclear or conflict arises with the proposed

staging of events, the appointed site arboriculturist must be consulted for

clarification or further guidance. The omission or avoidance of any instruction

provided below renders the information provided null and void.


2.1 PHASE 1 – Pre commencement

2.1.1 The contractor must appoint an independent arboriculturalist to oversee the

project who will monitor, record and confirm the implementation and

maintenance of tree protection measures and method statements. This

person must be an arboriculturalist as defined within BS 5837:2005 and

must not be an employee of the client, the design team or the contractor.

2.1.2 Prior to commencement of any activity on site, the contractor must arrange

and effect a pre - commencement meeting between the appointed

arboriculturalist, a design team representative and project manager to review

and confirm extent of arboricultural involvement, the scheduling of site visits

and the efficacy of tree protection measures. This will allow the identification

of any design changes since the completion of arboricultural implication

assessments and the resolution of any remaining foreseeable issues prior to

vehicle movements on site. A summary of the decisions made and the final

schedule of inspections will be recorded by the arboriculturalist and where




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necessary (such as the amendment of tree protection plans or barrier

specifications) agreed with the Norfolk County Council tree officer in writing.

Confirmation of subsequent agreement will be forwarded to the design and

construction representatives to allow commencement.

2.1.3 The contractor must retain a copy of the tree protection plan (see appendix

2) on site and the project manager will be responsible for communicating the

recommendations of this method statement to all staff and operatives on

site.

2.2 PHASE 2 – Root investigations

2.2.1 A root investigation trench must be undertaken along the line of the

proposed access road where it lies within the RPA of T9 and T11 in order to

inform the final construction. The extent of the roadway and the calculated

RPAs should be marked out in advance by the contractor using the

dimensions given in the tree survey schedule within the associated

Arboricultural Implications Assessment (MAN/THTAC/AIA/01A) (a copy has

been included within Appendix 1).

2.2.2 The investigation will involve the excavation (either by the appointed

arboriculturalist or under their supervision) of a trench using an excavator

with an un-toothed bucket to a minimum depth of 600mm (or the proposed

construction depth, whichever is greater) with a width no greater than

300mm. Due to the distance anticipated (± 40 metres) the trench should be

broken into multiple two metre trenches if considered appropriate by the



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appointed arboriculturalist provided the distance between trenches does not

exceed two metres.

2.2.3 If roots are discovered, excavation must cease although exposure of the

discovered roots to assess their significance can be achieved using hand

tools if considered appropriate. The appointed arboriculturalist will document

the findings of the investigative trench (including the location of significant

roots above 25mm in diameter) and propose recommendations for

construction depending on the revealed root morphology which must be

communicated to both the design team and the Norfolk County Council Tree

Officer. The trench will be promptly backfilled on completion with areas

suitable for re-excavation by hand clearly marked.

2.2.4 Final design will be prepared by a suitable qualified and competent individual

based on the recommendations of the appointed arboriculturalist. The details

(which will include final levels) must be agreed with the LPA Tree Officer

before commencement.

2.3 PHASE 3 - Implementation tree works

2.3.1 If the specification for tree works is older than 12 months or relates to trees

that have experienced a material change in circumstances (i.e., have been

subjected to construction traffic) then the appointed arboriculturalist will re-

inspect the site and ensure that the specified works detailed in the tree

survey schedule within the associated Arboricultural Implications

Assessment (MAN/THTAC/AIA/01A) remain relevant and necessary (a copy



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has been included within Appendix 1). This includes any trees to be removed

or pruned to facilitate the development or vehicle access that have been

subsequently identified as necessary to the scheme and that are agreed

(either directly or implicitly) as part of the proposal.

2.3.2 All tree works must be carried out by a suitably qualified arborist appointed

by the project manager; preferably one from the Arboricultural Association

Approved contractors list or by an ISA certified Arborist. All works must

comply with BS 3998:2010. After completion of all specified tree works, the

project manager will notify the appointed arboriculturalist.

2.3.3 The appointed arboriculturalist must inspect all completed tree works prior to

commencement of any construction to ensure full compliance with the

approved specification. This inspection may coincide with the inspection of

tree protection measures required by the following stage.

2.3.4 Should any further tree work become necessary as a result of unforeseen

circumstances, a specification schedule detailing the proposed works must

be produced by the appointed arboriculturalist and agreed by the LPA Tree

Officer in writing prior to implementation.

2.4 PHASE 4 - Implementation of tree protection measures

2.4.1 All tree protection barriers will be installed by the construction team as

shown on the agreed tree protection plan prior (101111/C in appendix 2)

prior to allowing any delivery of construction materials / plant or works

connected with the development. These will be constructed using weld mesh



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panels on a framework of scaffolding or similarly sturdy material driven into

the ground to a suitable depth to ensure its stability and compliance with

BS5837:2005 Figure 2. Weatherproof notices must be attached to the tree

barriers stating; “Construction Exclusion Zone - Keep Out” and including the

contact details of the appointed arboriculturalist and the LPA Tree Officer.

The project manager will notify the appointed arboriculturalist upon the

completion of the installation of all barriers.

2.4.2 The appointed arboriculturalist will undertake a site inspection within 24hrs of

notification of the above to confirm and record that all tree protection

measures are fit for purpose and correctly positioned (and that all facilitation

pruning has been undertaken correctly if not previously recorded). The

condition of the trees will be cross referenced with the preceding survey and

any discrepancies noted and photographically recorded where appropriate.

Any arboricultural issues that arise (such as accidental damage) will be

resolved in agreement with the Norfolk County Council tree officer and

recorded. Confirmation of the installation of tree protection measures and

any material change in tree condition or health will be forwarded to the

project manager and LPA tree officer in writing.

2.4.3 All tree protection measures must remain in place until the end of the

development period, it will be the responsibility of the project manager to

ensure all such protection remains in place and any sections damaged duly

repaired or replaced as a matter of high priority. If for any reason any section

needs to be moved then the appointed arboriculturalist must first be

consulted.



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2.5 PHASE 5 – Demolition and Construction

2.5.1 Due to the space afforded by pre-commencement tree removals and the

installation of tree protection all required demolition of structures and

subsequent construction can be undertaken any time after the confirmation

by the appointed arboriculturalist (see section 2.4.2) with the exception of the

following elements.

2.5.2 The areas of the existing surface within the tennis courts that are within the

assessed RPAs of the retained trees within G6 must be removed under

supervision by the appointed arboriculturalist. This can be undertaken using

an excavator with an un-toothed bucket to lift sections of the surface for

removal by hand. Where it is assessed by the appointed arboriculturalist that

there is a risk of damaging significant roots, hand tools should be used to lift

and break the surface. After removal of the surface, an assessment should

be made by the appointed arboriculturalist regarding the suitability of

retaining the sub-base and method of its removal should that be considered

appropriate. Any exposed roots must be covered by between 100 - 300mm

of good quality topsoil within eight hours of their exposure.

2.5.3 The pile or post locations for the proposed suspended walkway pedestrian

crossover that are within two metres of the base of either T9 or T14 must be

excavated by hand to the required depth. The embankment may be scraped

clear of vegetation to depth of no more than 150mm using hand tools only.

Any machinery used to auger the reminder of the post holes or drive piles

must operate from suitable ground protection as identified by the appointed

arboriculturalist.



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2.6 PHASE 6 - Completion

2.6.1 Upon completion of the project and after construction and vehicle

movements of site have finished, tree protection will be removed by the

construction team. Subsequently, the project manager will notify appointed

arboriculturalist of its removal.

2.6.2 The appointed arboriculturalist will undertake a final site inspection within

48hrs of notification of the above. The condition of the trees will be cross

referenced with the preceding surveys, any discrepancies noted and

photographically recorded where appropriate. Any arboricultural issues that

arise (such as accidental damage) will be resolved in agreement with the

Norfolk County Council tree officer and recorded. Confirmation of the

removal of tree protection measures and any material change in tree

condition or health will be forwarded to the project manager and Norfolk

County Council tree officer in writing.

2.6.3 The appointed arboriculturalist will produce a compliance report summarising

the combined notes and history of the development with regard to the trees.

If tree protection has been maintained and method statements followed

effectively this can demonstrate a proactive approach, diminish claims of

negligence and help discharge relevant planning conditions prior to

handover. This report will include an overview of the impact of the

development on the trees and propose any final amelioration or mitigation

works that are necessary. This will be submitted to the project manager and

Norfolk County Council tree officer.

Appendix 2 – Survey Schedule Explanation

The following schedule details the results of the tree survey undertaken on the date referred to in section 2.1.1. This information is used to create the tree constraints plan and forms the base assessment for the conclusions and recommendations within the main text. Below is an example section of a schedule with an explanation of its component parts.

Tree ID No.

Common Name

Botanical Name

Maturity Height (m)

Stem Dia.

(mm)

Spread (m) Position and height of lowest

canopy (m)

Condition

Comments

Recommendations Remaining Contribution

BS5837: 2005

Category

RPA Radius

(m) RPA m²

N E S W Root Zone Stem Canopy Physio.

T1 Walnut Juglans regia

Mature 10 640 6 7 9 6 W - 2 Fair Good Fair Good Minor branch stub cavities on main stem.

No work at this time. 40+ Years A2 7.68 185.3

T2 Common Ash

Fraxinus excelsior

Mature 16 300 6 6 8 7 N - 4.5 Fair Bad Fair Good Twin stemmed structure with southern stem sweeping (due to suppression) to vertical over road

with significant end loading. Visible adaptive bulges on underside of

stem. Old annual I. hispidus brackets midway along leaning stem on tension side at point of

union with dead branch. Northern stem is currently sheltered and is

beyond the acceptable threshold of h/d = 50 (16m/300mm = 53.5).

Fell to ground level and grind stump to >300mm. Back fill with

screened topsoil to BS3882:2007 and seed with appropriate and consistent grass seed. Replant with one standard size (8-10cm girth) Common Ash - Fraxinus

excelsior subject to agreement of location, specification and methodology with the LPA.

40+ Years R 3.6 40.7

Alphanumeric reference assigned to allow cross referencing between all plans and within the main text.

Stem diameter is measured at 1.5m from ground level for trees with a single stem at that height. Where this is not the case, the measurement is taken just above the basal root flare (where the stem diameter becomes consistent narrower).

Defines the relative stage of the tree’s development within the environment as follows: NP – Newly Planted; Young - <33% Life expectancy (LE); Semi Mature – 33-66% LE; Mature – 66-100% LE; Over Mature - >100% LE.

Lateral canopy spread as measured at the four cardinal points (north south, east & west).

The Root Protection Area (RPA) of the tree is calculated from the stem diameter as per section 5.2.2 of BS5837:2005. The subsequent shape of this area on the constraints plans must reflect site conditions and tree habit. The adjacent column shows the same area as an idealised radial model.

Tree category in accordance with section 4.3.1 and Table 1 of BS5837:2005. Retention categories include A, B, C with those rated R typically identified for removal. Subcategories (numbers) reflect particular values to aid assessment. Text is coloured to correspond with the plans.

Orientation (N, S, E or W) and height from adjacent ground level of the lowest point of the canopy. Where only one side of the canopy has the potential to be affected by development this details will be included to maintain relevance.

Comments include details of any identified structural defects, notes on form and location. Subsequent recommendations include any necessary remedial work specifications and reference to any replacement planting (subject to details within the main conclusions).

The estimated remaining contribution of the trees (as per section 4.2.6 of BS5837: 2005) in the existing environment precluding any development. This information typically informs the categorisation of the trees (adjacent).

Summarises the structural condition of the basic parts of the tree/s and its overall physiological (abbreviated to Physio.) state as follows: Bad – Significant irredeemable defect; Poor – Significant defects redeemable by significant pruning works; Fair – Minor defects redeemable by significant pruning works; Good – No defects present or inconsequential defects not requiring any practical works; Decline – Progressive and irreversible physiological deterioration; Dead - >90% moribund or dysfunctional tissue present.

Appendix 1 - Tree Survey ScheduleThetford Academy, Croxton Road, Thetford

Ravencroft Arboricultural Services Ltd.Surveyed - 15.06.11 07.11.11

KEYT - Tree / G - Group / H - Hedge / W - Woodland

NB: The suffix 'E' indicates that the dimension is estimated.

N E S W Root Zone Stem Canopy Physio.

T1 English Oak Quercus robur Semi - Mature

10 290 5 5 5 5 1.5 - N Fair Poor Fair Good Chain around base (securing picnic table) causing significant constriction to stem.

Remove chain where it can be freely pulled away. Any included sections to be cut in situ and left.

20 - 40 Years B 3.48 38.1

T2 Ash Fraxinus excelsior Semi - Mature

9 260 4 3.7 3.7 5 3.5 - W Fair Fair Fair Fair No significant visible defects. No work at this time. 20 - 40 Years B2 3.12 30.6

T3 Ash Fraxinus excelsior Mature 17 850 9 5 7 11 3.5 - W Poor Poor Poor Poor Possible fire damage on stem and lower limbs. Woodpecker holes visible. Multistemmed structure.

Fell to ground level to faciliate development. <10 Years R 8.5 227.0

T4 Ash Fraxinus excelsior Mature 18 500 4 6 7 6 10 - S Obscured by ivy

Obscured by ivy

Fair Fair No significant visible defects. Form indicative of woodland growth with no lower limbs.

Fell to ground level to faciliate development. 20 - 40 Years B2 6 113.1

T5 Ash Fraxinus excelsior Semi - Mature

17 450 6 6 4 6 12 - N Fair Poor Poor Decline Thin canopy and potential hollowing beneath bark to the north.

Fell to ground level to faciliate development. < 10 Years R 5.4 91.6

T6 Ash Fraxinus excelsior Dead 13 400 2 2 2 2 5 - S Obscured by ivy

Obscured by ivy

Obscured by ivy

Dead Ivy covered. Previous branch failures visible.

Fell to ground level to faciliate development. < 10 Years R 4 50.3

T7 Hawthorn Crataegus monogyna Dead 7 500 4 4 4 4 3 - N N /A N/A N/A Dead Ivy covered. Previous branch failures visible.

Fell to ground level to faciliate development. < 10 Years R 6 113.1

T8 English Oak / Ash

Quercus robur / Fraxinus excelsior

Semi - Mature

9 350 5 5 5 5 3.5 - S Obscured by epicormic growth

Obscured by ivy

Fair Fair Interlocked individuals of Oak and Ash. Constricted unions between limbs.


T9 English Oak Quercus robur Mature 11 1000 7 7 7 7 5 - N Obscured by ivy

Obscured by ivy

Poor Poor No significant visible defects. Sever Ivy stems to 1.5m from ground level around entire circumference of host tree.

20 - 40 Years B2, 3 12 452.4

T10 Field Maple Acer campestre Semi - Mature

8 600 4 4 4 4 2 - S Obscured by ivy

Obscured by ivy

Good Fair No significant visible defects. Sever Ivy stems to 1.5m from ground level around entire circumference of host tree.

10 - 20 Years B 6 113.1

T11 Ash Fraxinus excelsior Mature 11 750 6 7 6 7 3 - N Obscured by ivy

Obscured by ivy

Good Good Two historic failures visible at 5m on the northwest canopy. No significant visible defects.

Sever Ivy stems to 1.5m from ground level around entire circumference of host tree.

20 - 40 Years B 9 254.5

T12 Ash Fraxinus excelsior Mature 13 700 4.5 4 7 6 2.5 - N Obscured by ivy

Obscured by ivy

Good Good No significant visible defects. Sever Ivy stems to 1.5m from ground level around entire circumference of host tree.

20 - 40 Years B 7 154.0


13 550 6 4 4 3 4 - S Fair Fair Fair Fair No significant visible defects. No work at this time. > 40 Years B 6.6 136.9


13 550 6 3 4 4 4 - S Fair Fair Fair Fair No significant visible defects. No work at this time. > 40 Years B 6.6 136.9

T15 Hawthorn Crataegus monogyna Mature 5 170 4 4 4 4 2.5 - W Fair Fair Fair Fair No significant visible defects. Fell to ground level to faciliate development. 20 - 40 Years C 2.04 13.1

T16 Hawthorn Crataegus monogyna Dead 5 170 4 4 4 4 2.5 - W N /A N/A N/A Dead Dead tree in hedgerow. Fell to ground level to faciliate development. < 10 Years R 2.04 13.1

T17 Sugar Maple Acer saccharum Semi - Mature

6 180 2 2 2 2 2 - S Fair Fair Poor Fair Pollarded at 2m. No significant visible defects.

No work at this time. 10 - 20 Years C 2.16 14.7

T18 Silver Birch Betula pendula Semi - Mature

12 180 4 4 4 4 3 - S Fair Fair Fair Fair No significant visible defects. Fell to ground level to faciliate development. 10 - 20 Years C 2.16 14.7

W1 English Oak / Beech / Ash / Larch / Hawthorn / Field Maple

Quercus robur / Fagus sylvatica / Fraxinus excelsior / Larix decidua / Crateagus monogyna / Acer campestre

Mature 15 400 5 5 5 5 4 - S Fair Fair Fair Fair Mixed condition trees with characeristic woodland form.

Fell selected edge trees on western edge in agreement with LPA Tree Officer. Advise client to implement a woodland management plan produced by a qualified and competant arboriculturalist.

> 40 Years B2 4.8 72.4

G1 English Oak Quercus robur Semi - Mature

9 300 5 4 5 5 2 - N Fair Fair Fair Fair No significant visible defects. No work at this time. > 40 Years B2 3.6 40.7

G2 English Oak / Ash

Quercus robur / Fraxinus excelsior

Semi - Mature

8 300 5 5 5 5 2 - N Obscured by ivy

Fair Fair Fair Five oaks and one twin stemmed Ash. No significant visible defects.

No work at this time. 20 - 40 Years B2 3.6 40.7

G3 Ash Fraxinus excelsior Semi - Mature

16 350 4 4 8 8 8 - S Obscured by waste.

Obscured by ivy

Fair Fair Partially composted green waste around base of trees.

Fell to ground level to faciliate development. 10 - 20 Years C 4.2 55.4

G4 Laburnum / Wild Cherry

Laburnum anagyroides / Prunus avium

Semi - Mature

9 400 4 4 4 4 2 - N Obscured by ivy

Obscured by ivy

Obscured by ivy

Fair No significant visible defects. Fell to ground level to faciliate development. 10 - 20 Years C 4 50.3

G5 Ash Fraxinus excelsior Mature 15 600 9 7 7 7 3 - W Obscured by ivy

Obscured by ivy

Fair Fair No significant visible defects. Fell to ground level to faciliate development. > 40 Years B2 6 113.1

G6 Scots Pine Pinus sylvestris Semi - Mature

9 300 5 5 5 5 0 - N Good Fair Good Good No significant visible defects. Fell northernmost subgroup (trees G6a to G6e) to ground level to faciliate development.

20 - 40 Years B2 3.6 40.7

G7 English Elm Ulmus procera Dead 8 350 3 3 3 3 3 - W N /A N/A N/A Dead Group of dead and dying trees typical of Dutch Elm Disease.


G8 Silver Birch Betula pendula Semi - Mature

10 300 5 5 5 6 2 - S Fair Fair Fair Good No significant visible defects. Fell to ground level to faciliate development. 20 - 40 Years B2 3.6 40.7


13 320 6 5 6 6 2 - S Fair Fair Fair Good No significant visible defects. No work at this time. 20 - 40 Years B2 3.84 46.3

Remaining Contribution

BS5837: 2005 Category

RPA Radius (m)

RPA m²Stem Dia. (mm)

Spread (m) Average height of lowest canopy (m)

Condition Comments RecommendationsHeight (m)

Tree ID Common Name

Botanical Name Maturity

Appendix 1 - Tree Survey ScheduleThetford Academy, Croxton Road, Thetford

Ravencroft Arboricultural Services Ltd.Surveyed - 15.06.11 07.11.11

KEYT - Tree / G - Group / H - Hedge / W - Woodland

NB: The suffix 'E' indicates that the dimension is estimated.

N E S W Root Zone Stem Canopy Physio.Remaining Contribution

BS5837: 2005 Category

RPA Radius (m)

RPA m²Stem Dia. (mm)

Spread (m) Average height of lowest canopy (m)

Condition Comments RecommendationsHeight (m)

Tree ID Common Name

Botanical Name Maturity


7 250 3 3 3 3 2 - S Fair Fair Fair Good No significant visible defects. Fell to ground level to faciliate development. 20 - 40 Years B2 3 28.3

G11 Scots Pine Pinus sylvestris Semi - Mature

8 350 4 4 4 4 2 - N Fair Fair Fair Good No significant visible defects. Fell to ground level to faciliate development. 20 - 40 Years B2 4.2 55.4



G13 Ash / Laburnum

Fraxinus excelsior / Laburnum anagyroides

Semi - Mature

7 250 2 3 2 3 3 - W Fair Poor Poor Fair Ash exhibit suppression form adjacent woodland and Laburnum is in terminal decline.

Fell to ground level to faciliate development. 10 - 20 Years C 2.5 19.6



H1 Field maple / Ash / Hawthorn

Acer campestre/ Fraxinus excelsior / Crateagus monogyna

Mature 5 150 2 2 2 2 0 - S Fair Good Fair Fair Mixed native hedge. No significant visible defects.

Remove section as shown on Proposed Tree Constraints Plan (Retained) 101111/B2

20 - 40 Years B 1.5 7.1

H2 Leyland Cypress

x Cuprocyparis leylandii

Mature 6 150 1 1 1 1 0 - N Fair Fair Fair Fair No significant visible defects. Fell to ground level to faciliate development. 10 - 20 Years C 1.5 7.1




Fell to ground level to faciliate development. 20 - 40 Years B 1.5 7.1





20 - 40 Years B 1.5 7.1





20 - 40 Years B 1.5 7.1

Documents

Arboricultural Ltd Method Statement Norfolk