STEPHEN CUTMORE BSc(Hons), MArborA

UK/I 0343A

STEPHEN CUTMORE BSc(Hons), MArborA

PRO3755

Arboricultural & Ecological Services

S U R V E Y S , I N S P E C T I O N S , R E P O R T S

21 Maes-y-Dre, Ruthin, Denbighshire. LL15 1DB

Email: [email protected]

Mobile: 07877120981 Tel: 01824 709650

BUILDING PLOT

(BETWEEN ‘Y CULFOR’ AND ‘CAE PYSGODLAN’)

BANGOR ROAD

CAERNARFON

GWYNEDD

LL55 1LN

ADVANCED TREE INSPECTION

UTILISING THE PICUS SONIC TOMOGRAPH AND

IML PD-400 RESISTOGRAPH

Report by:

Stephen Cutmore BSc (Hons), MArborA I.S.A. Certified Arborist U/I-0343A,

I.S.A Tree Risk Assessment Qualified

Client Kyra Beguiristan

Planning Authority Gwynedd County Council

Date of Survey 21 April 2017

Grid Reference SH488 639

Reference 042017/ATI-KB



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TABLE OF CONTENTS

1.0 SUMMARY 3

2.0 INTRODUCTION 4

2.1 Brief

2.2 Purpose of this report

2.3 Scope of this report

2.4 Relevant background information 5

2.5 Tree identification and location

2.6 Qualifications

2.7 Copyright

3.0 DATA COLLECTION 5

3.1 Site visit

3.2 Site description

3.3 Methodology 6

3.4 Results 7

4.0 APPRAISAL

4.1 Analysis of IML PD-400 Resistograph drillings 8

5.0 CONCLUSIONS 9

6.0 RECOMMENDATIONS 9

APPENDICES

APPENDIX 1 – Site plan 10

APPENDIX 2 – Picus Sonic Tomographs 11

APPENDIX 3 – Resistograph drill readings 13

APPENDIX 4 - Photographs 21

APPENDIX 5 – Bibliography 22

Client: Kyra Beguiristan Picus Tree Report 24 April 2017

Ref: 042017/ATI/KB Bangor Road, Caernarfon page 2 of 36



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1.0 SUMMARY

An advanced inspection was carried out on the three Beech trees (T1, 8 & 9), using hi-tech

decay detection equipment. The Picus Sonic Tomograph (SoT) utilises ultra-sonic

soundwaves to assess the internal condition of the trunk cross-section being tested.

The PD-400 Resistograph micro-drill drills a narrow diameter drilling needle into the wood,

whilst recording the resistance of the wood against the cutting tip. High resistance indicates

healthy wood, low resistance indicates defects in the wood (decay, cracks etc.).

Various researchers have devised mathematical equations regarding the safety factors of

trees, based on scientific evidence that a hollowing tree can remain stable providing that there

is a residual wall of solid, healthy wood around the periphery of the trunk. A ratio of

residual wall thickness to the radius (t/R) of 0.3 is given as a rough guideline for safety, for

tall trees with a full canopy exposed to wind-loading [Mattheck, Bethge and Weber, 2015].

The SoT showed a central cavity in the base of Beech T1. The PD-400 drillings confirmed a

central cavity and indicated that the 1/3 radius safety margin has been breached at MP2 and

MP7. The conclusion is that the tree is in a critical condition. The advanced decay/cavity

will likely increase in intensity and extent over the next few years. The tree is posing an

increasingly high risk to the high value targets in the danger zone (people, vehicles using

Bangor Road). The recommendation is to section-fell the tree to ground level for safety

reasons.

The PD-400 drillings for Beech (T8) confirmed the 1/3 radius safety margin remains intact at

this time. The conclusion is that the tree can be safely retained at this time. The

recommendation is to crown reduce the tree by 25%.

The SoT indicated an open cavity in the east of the trunk base of Beech T9. The narrow

transition from solid wood to decay indicates a strong defensive barrier is present in the

wood. The 1/3R safety margin remains intact at this time. The defensive barrier is inhibiting

the spread of the fungus into the rest of the trunk cross-section at this time. The conclusion is

that the tree can be safely retained at this time. The recommendation is to crown reduce the

tree by 25%.





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2.0 INTRODUCTION

2.1 Brief

Stephen Cutmore BSc (Hons), MArborA, was instructed by Kyra Beguiristan, in the form of a

telephone conversation on 18 April 2017, to carry out an advanced tree inspection of three

mature Beech trees on the building plot, (between ‘Y Culfor’ and ‘Cae Pysgodlan’), Bangor

Road, Caernarfon, Gwynedd, LL55 1LN.

The definition of the assignment was to:

1. Carry out an Advanced Tree Inspection of the three Beech trees, utilising hi-tech decay

detection tools.

2. Assess the condition of the trees.

3. Provide a report with management options.

2.2 Purpose of this report

The purpose of this report is to advise you of the results of the parts 1-2 of the assignment.

These results are set forth in the Conclusions section, following. This report describes the

field conditions as found and interpreted.

2.3 Scope of report

Date of consultation.

The field examination was made on 21 April 2017, and observations and conclusions are as

of that date.

Limit of scope.

This is solely an Arboricultural Report and cannot comment on topics outside this discipline.

If additional advice is required, it is strongly recommended that other professionals are

consulted e.g. Structural Engineers or Surveyors.

1) information contained in this report covers only those trees that were examined and

reflects the condition of those trees at the time of the inspection: 2) the inspection is limited

to visual examination of the subject tree from ground level only and 3) specialist hi-tech

equipment was utilised to assess the internal condition of some of the trees.





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2.4 Relevant background information

During a recent tree survey, three mature Beech trees were identified as having decay present

in the trunks. If there is significant decay present in the Beech trees, they could pose a high

risk to public safety.

2.5 Tree identification and location

The subject trees were identified in my previous report [Tree Condition Survey to BS5837

(2012), dated 6 January 2017] as T1, T8 and T9. The trees are located within the boundaries

of the building plot, (between ‘Y Culfor’ and ‘Cae Pysgodlan’), Bangor Road, Caernarfon,

Gwynedd, LL55 1LN. Beech tree (T1) is located on the south-east boundary adjacent to the

busy A487 Bangor Road. The other two trees (T8 & T9) are located near to the north-west

boundary of the site, within falling distance of the neighbouring residential property located

to the north-east. The locations of the trees are shown on the site plan, attached as Appendix

1.

2.6 Qualifications

Stephen Cutmore has over thirty years’ experience in the arboricultural and forestry industry

as a contractor and has over twenty years’ experience as an arboricultural consultant.

Stephen holds a BSc (Hons) in Arboriculture & Urban Forestry and is a Certified Arborist

UK/I-0343 [International Society of Arboriculture]. Stephen is a Professional Member of the

Arboricultural Association (MArborA) and is also an Associate Member of the Institute of

Chartered Foresters, currently working through the Institute’s Professional Membership Entry

towards Chartered status. Stephen has attended three Masterclasses for the Picus and one

Masterclass for the Resistograph, run by the UK distributors, Sorbus International and has

specialist knowledge in advanced tree inspections utilising hi-tech decay detection

equipment.

2.7 Copyright

Copyright © 2017 by Stephen Cutmore. All rights reserved. This report or any parts thereof

may not be reproduced without the prior written permission of the author.

3.0 DATA COLLECTION

3.1 Site visit

A site visit was made on the morning of 21 April 2017. The weather was dry and sunny.

There were no limiting factors to the inspection.

3.2 Site Description

The site is an unmanaged pasture field, with predominantly mature age class broadleaved

trees located around the boundaries. Residential properties are located either side of the plot

and a horse paddock field is adjacent to the north-west boundary. The A487 Bangor Road is

adjacent to the south-east boundary.





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3.3 Methodology

An advanced inspection of the three Beech trees, utilising specialist decay detection

equipment, was carried out.

The data obtained in the advanced inspections was analysed and the condition of the trees

were assessed.

Picus Sonic Tomograph

Two Beech trees (T1 and T9) were tested with the Picus Sonic Tomograph (non-invasive

technique) to assess the internal condition of the trunks near the base. The Picus Sonic

Tomograph works on the basis that solid wood is a better sound transmitter than decayed

wood. Sonic sensors were strategically spaced around the circumference of the trees, to detect

stress-waves induced by manual impact and propagated through the wood. Electronic

callipers were used to accurately plot the positions of the sensors. A computer analysed the

data and generated a two-dimensional colour sonic tomograph (SoT) of the cross-section,

detailing areas of solid wood, decay and cavities within the tree. On the tomograph, brown

colours indicate solid, healthy wood. The colours green, violet and blue indicate increasing

degrades of decay. The SoT tomographs are included as Figures 1 and 2 and also as

Appendix 2.

IML PD-400 Resistograph microdrill

Following the Picus Sonic Tomograph assessment, a further assessment of Beech T1 was

made near the base, utilising the IML PD-400 Resistograph. An inspection was also carried

out on Beech (T8), which had an open cavity extending some distance up the north-east

trunk. The PD-400 Resistograph is a precision tool, used to accurately assess the internal

condition of trees. The device has a narrow 2mm diameter drilling needle with a maximum

drilling length of 400mm. As the drilling needle is drilled into the wood at a constant

velocity, the resistance of the wood against the tip of the drill-bit is digitally recorded. High

resistance indicates solid, healthy wood. Low resistance indicates defects in the form of

decayed wood, cavities, cracks, etc.

Four drill tests were carried out around the trunk of Beech (T1) at 20cm height and one drill

test at 10cm height. Three drillings were carried out on the north-east trunk of Beech (T8) at

4m height. The Resistograph readings are included as Appendix 3.





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3.4 Results

Picus Sonic Tomograph

Beech T1

Figure 1: SoT of Beech T1 at 20cm above ground.

The SoT indicates a decay cavity (blue colour) across the centre of the trunk and extending

towards the south side of the trunk [Measuring Point 7], with associated advanced decay

(violet colour) and early-stage decay (green colour). Solid wood (brown colour) is shown

around the trunk periphery. The light brown colour indicates a reduction in the sonic

velocity, where a fungus may have inoculated the wood, but not yet degraded the cell walls of

the wood cells. The superimposed red line indicates the 1/3 radius safety margin.

Beech T9

Figure 2: SoT of Beech T2 at 10cm above ground.

The SoT indicates an open decay cavity on the east of the trunk [MP9-10]. The tomograph

indicates a small amount of advanced decay and early-stage decay around the inner margins

of the cavity. The rest of the trunk cross-section is shown as solid wood. The light brown

colour indicates a reduction in the sonic velocity, where the fungus has inoculated the wood,

but not yet degraded the cell walls of the wood cells. The superimposed red line indicates the

1/3 radius safety margin.





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3.4 Results (continued)

IML PD-400 Resistograph

Beech T1

Test #1(MP2): The drilling shows sound wood until 17.3cm before encountering advanced

decay/cavity.

Test #2(MP5-6): The drilling shows sound wood until 30cm before encountering advanced

decay/cavity.

Test #3(MP7): The drilling shows sound wood until 18.9cm before encountering advanced

decay/cavity.

Test #4(MP9-10): The drilling shows sound wood until 30.7cm before encountering

advanced decay/cavity.

Test #5(MP5-6) at 10cm above ground: The drilling shows sound wood until 25.7cm before

encountering advanced decay/cavity.

Beech T8

Test #6: The drilling shows sound wood until 24.1cm before the needle automatically

retracted when constant pressure on the handle was interrupted.

Test #7: The drilling shows sound wood until 30.7cm before the needle automatically

retracted when constant pressure on the handle was interrupted.

Test #8: The drilling shows sound wood until 35.1cm before encountering advanced

decay/cavity.

4.0 APPRAISAL

4.1 Analysis of IML PD-400 Resistograph drillings

Various researchers have devised mathematical equations regarding the safety factors of

trees, based on scientific evidence that a hollowing tree can remain stable providing that there

is a residual wall of solid, healthy wood around the periphery of the trunk. A ratio of

residual wall thickness to the radius (t/R) of 0.3 is given as a rough guideline for safety, for

tall trees with a full canopy exposed to wind-loading [Mattheck, Bethge and Weber, 2015].

Beech T1

The circumference of Beech T1 at the position of the test was 3880mm. The diameter

calculates as 123.5cm [C= πd]. The one-third radius safety margin calculates as 20.56cm.

Tests #1 and #3 encountered advanced decay/cavity at 17.3cm and 18.9cm drilling depth

respectively. Tests #2 and #4 encountered advanced decay/cavity at 30cm and 30.7cm

respectively. Test #5 was made at 10cm height and encountered advanced decay/cavity at

25.7cm. The Resistograph drills confirm a decay cavity is developing in the centre of the

trunk and that the 1/3R safety margin has been breached at Tests #1 and #3. Client: Kyra Beguiristan Picus Tree Report 24 April 2017




Mobile: 07877120981 Tel: 01824 709650

4.1 Analysis of IML PD-400 Resistograph drillings (continued)

Beech T8

The diameter of the north-east stem of Beech T8 at 4m height was 70cm. The one-third

radius safety margin calculates as 11.67cm. Test #6 indicated that the drilling needle

encountered sound wood until 24.1cm, before the needle automatically retracted when

constant pressure on the handle was interrupted. Test #7 indicated that the drilling needle

encountered sound wood until 30.7cm, before the needle automatically retracted when

constant pressure on the handle was interrupted. Test #8 indicated that the drilling needle

encountered sound wood until encountering advanced decay/cavity at 35.1cm. The 1/3R

safety margin remains intact at all three test positions at this time.

5.0 CONCLUSIONS

Beech T1

The SoT shows a central cavity developing across the base of the trunk. The wide transition

zone between solid wood (brown) and decayed wood (green, violet and blue) indicates a

weak defensive barrier in the wood. The fungal decay is likely to increase in intensity and

extent over the next few years. The Resistograph drillings all encountered advanced

decay/cavity and the results confirm the 1/3R safety margin has been breached at MP2 and

MP7. The conclusion is that Beech T1 is in a critical condition and there is an increasingly

high risk to vehicles and pedestrians on the adjacent Bangor Road.

Beech T8

The Resistograph drillings confirm the 1/3R safety margin remains intact. The conclusion is

the tree is safe to retain at this time.

Beech T9

The SoT shows an open cavity on the east of the trunk at MP9-10. There is a narrow

transition zone between solid wood and decay, indicating a strong defensive barrier in the

wood. There is solid healthy wood around the rest of the trunk periphery and the 1/3R safety

margin remains intact. The conclusion is the tree is safe to retain at this time.

6.0 RECOMMENDATIONS

The recommendation for Beech T1 is to section-fell to ground level for safety reasons.

The recommendation for Beech T8 and T9 is to crown reduce by 25%, by shortening the

branches back by 2-3m to a suitable lateral branch.

The work should be carried out by a qualified and insured arborist to comply with BS3998

(2010) ‘Recommendations for Tree Work’.

Report written and compiled by

Stephen Cutmore BSc (Hons), MArborA,

I.S.A. Certified Arborist UI-0343A, I.S.A. Tree Risk Assessment Qualified





Mobile: 07877120981 Tel: 01824 709650

APPENDIX 1 – Site plan (to scale)





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APPENDIX 2 – Picus Sonic Tomograph

Plate 1: Sonic tomograph of Beech T1 at 20cm.





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APPENDIX 2 – Picus Sonic Tomograph

Plate 2: Sonic tomograph of Beech T9 at 10cm.





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APPENDIX 3 – IML PD400 Resistograph drillings

Plate 3: Resistograph test Beech T1 #1





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Plate 4: Resistograph test Beech T1#2





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Mobile: 07877120981 Tel: 01824 709650

APPENDIX 5 – Photographs

Photo 1: Basal cavity in Beech T1.

Photo 2: North-east stem of Beech T8, showing Resistograph test locations.

Photo 3: Basal cavity in Beech T9.





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APPENDIX 6 – Bibliography

The following publications were referred to in preparing this report.

Lonsdale, D (1999). Principles of Tree Hazard Assessment and Management. Research for

Amenity Trees No.4. HMSO, London, UK.

Mattheck, C., Bethge, K. and Weber, K. (2015). The Body Language of Trees. Encyclopedia

of Visual Tree Assessment. K.S Druck, Kronau, Germany.

Mattheck, C. and Breloer, H. (1994). The Body Language of Trees. A Handbook for Failure

Analysis. HMSO, London, UK.

Schwarze, F.W.M.R (2008). Diagnosis and Prognosis of the Development of Wood Decay in

Urban Trees. Enspec, Rowville, Australia.



Documents

STEPHEN CUTMORE BSc(Hons), MArborA