TREE HEALTH AND STRUCTURAL INTEGRITY REPORT

Transcription

1 TREE HEALTH AND STRUCTURAL INTEGRITY REPORT OUR REF: JM/5721 R/mp YOUR REF: DATE: 24 th October 2012 CLIENT: SITE ADDRESS: Mr David Walker Writtle Parish Council Writtle Green Writtle. Essex DATE/TIME OF VISIT: Tuesday 16 th October 2012 PEOPLE PRESENT: REPORT COMPLETED BY: Mr J Mills and Mr L Smith Mr Jason Mills Note In reading and understanding the contents of this report it should be remembered that no tree can be deemed risk free. As with all things in the natural environment, they are subject to unpredictable forces such as extreme weather, effects of disease, and man s influence upon them. We investigate every obvious and available facet of the tree s structure and its surroundings in reaching a conclusion as to a level of risk. These conclusions and recommendations seek to reduce the level of risk the trees may pose to one that could be considered acceptable, given the tree s location, site use, and owners acceptance of the level of risk and the perception of its value to the environment. No tree can ever be considered completely hazard free, and regular monitoring of the tree and its surroundings should be undertaken by the owner and their appointed specialist advisors, where necessary on a cyclic and recorded basis. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 1 of 17

2 REPORT REFERENCES As a progressive company, we keep abreast of research data relating to arboriculture. All observations, recommendations and works are based on current industry standard reference material and extensive FA Bartlett research findings derived from the company s own facilities at University of Reading UK and Charlotte in the USA. A selection of pertinent items is shown in Appendix two. REPORT LIMITATIONS Observations were made from the ground level and the tree was not climbed. All tree risk assessments undertaken during surveys or inspections either on single trees or multiples of trees, use the methodology established by the International Society of Arboriculture, in the publication, Best Management Practice Tree Risk Assessment (Smiley, Matheny and Lilly 2011) and in the F.A. Bartlett publication Tree Risk Management (Smiley, Fraedrich, Hendrickson 2009), Principles of Tree Hazard Assessment and Management (HMSO Lonsdale 1999), Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines, 4 th Edition (Harris, Clark and Matheny 2004). This format may be specifically detailed in text related to reports on single and smaller groups of trees but will be implicit for large scale surveys unless specified to the contrary by the client. It is not possible to maintain trees free of risk, some level of risk must be accepted in order to experience the full range of benefits that trees provide. As such we reference the recently published document by the National Tree Safety Group (NTSG), Common sense risk management of trees (Forestry Commission 2011). This document provides guidance on trees and public safety in the UK for owners, managers and advisors. TREE PRESERVATION ORDER PROTECTION Tree Preservation Order (TPO) and Conservation Area (CA) status has not been confirmed. It would be advisable to check the status of the tree with the Local Authority before any tree works are carried out. AERIAL PHOTOGRAPH T13 Willow T12 Willow T18 Common Lime T19 Common Lime T7Silver Birch F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 2 of 17

3 TREE DETAILS The trees were visited on Tuesday 16 th October by Mr Jason Mills and Mr Lee Smith. A Silver Birch (Betula pendula), two Weeping Willow (Salix babylonica) and two Common Lime (Tilia x europaea) trees were inspected. T7 Silver Birch is located on the Eastern tip of the green. T12 and T13 Weeping Willow are adjacent the duck pond. T18 and T19 are on the Southern boundary of the green, next to a public road. The trees have been inspected following recommendations included within the tree survey carried out in 27 th February 2012, ref; OB/5721. T7 Silver Birch is 12.0 metres tall and has a stem diameter of 430mm at 1.5 metres above ground level and a basal diameter of 950mm. The crown predominates to the North with a spread of 8 metres. Crown spread to the east is 7.0 metres and 3.0 metres to the South and West. T12 Weeping Willow is 18.0 metres tall and has a stem diameter of 890mm at 1.5 metres above ground level and a basal stem diameter of 1500mm. The mean crown spread of the tree is 6.0 metres. T13 Weeping Willow is 18.0 metres tall and has a stem diameter of 920mm at 1.5 metres above ground level and a basal stem diameter of 1250mm. The crown spread of the tree is 7.5 metres to the north, 3.0 metres to the east, 6.0 metres to the south and 9.0 metres to the west. T18 Common Lime is 20.0 tall and has a stem diameter of 600mm at 1.5 metres above the ground and a basal diameter of 1500mm. The crown spread of the tree is 5.7 metres to the north, 4.8 metres to the east, 4.6 metres to the south and 4.8 metres to the west. T19 Common Lime is 8.0 metres tall and has a stem diameter of 640mm at 1.5 metres above ground level and a basal stem diameter of 820mm. The mean crown spread of the tree is 4.0 metres. There is public access beneath the canopy of all of the inspected trees. T12 and T13 have a high level of pedestrian activity under their canopies due to their location next to the duck pond. Tree Evaluation The tree s root flare and buttresses above ground were inspected and, where necessary, were probed. The stem, main scaffold limbs were visually inspected and probed where required. The trees crown, main branch framework and shoot extension growth were inspected from the ground with the aid of binoculars. Any accessible limb or stem unions suspected of having decay or cracks were also probed. Results from these assessments are included in the summary of tree visual assessment. Additionally evidence of fungal activity, and disease was investigated and recorded where noted. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 3 of 17

4 THE TESTS; USING A SONIC TOMOGRAPH (PICUS) One PICUS* test was made on each tree at the point of concern indicated in the tree survey to establish the extent of decay within the main stems. The test for T7 Silver Birch was carried out at 10 centimetres above ground level, T12 Weeping Willow at 120 centimetres above ground level, T13 Weeping Willow at 250 centimetres above ground level, T18 Common Lime at 15 centimetres above ground level and T19 Common Lime at 10 centimetres above ground level. *PICUS testing (Sonic Tomograph) enables almost un-injurious testing of a suspect tree stem. Sensor units are attached to adjustable webbing and small nails are driven into the bark to contact the sapwood tissue beneath. Each of the twelve nails are struck with a test hammer. Each blow is picked up by the sensor array around the tree stem (sound travels fastest through solid wood and very slowly through decay). The relative speeds of reception are uploaded onto a data file and processed into a visual image of the interior of the tree stem, using the software provided with the Sonic Tomograph. This image indicates solid wood (Brown colours) to voids/damaged tissue (Purple/Blue colours). This information is for inclusion along with other data in the overall assessment of a tree s condition. For each test, sensor one was located on the north side of the main stem and the subsequent sensors were spaced at regular intervals around the base of the trees. PHOTOGRAPH OF LOCATION OF SENSORS The photograph above shows the sensors attached to the main stem of T7 Silver Birch at 10 centimetres above ground level. The photograph above shows the sensors attached to the main stem of T12 Weeping Willow at 120 centimetres above ground level. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 4 of 17

5 The photograph above shows the sensors attached to the main stem of T13 Weeping Willow at 250 centimetres above ground level. The photograph above shows the sensors attached to the main stem of T18 Common Lime at 15 centimetres above ground level. The photograph above shows the sensors attached to the main stem of T19 Common Lime at 10 centimetres above ground level. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 5 of 17

6 RESULTS OF SONIC TOMOGRAPH (PICUS) TESTS The picture above shows the PICUS test carried out at 10 centimetres above ground level for T7 Silver Birch. The picture above shows the PICUS test carried out at 120 centimetres above ground level for T12 Weeping Willow. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 6 of 17

7 The picture above shows the PICUS test carried out at 250 centimetres above ground level for T13 Weeping willow. The picture above shows the PICUS test carried out at 15 centimetres above ground level for T18 Common Lime. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 7 of 17

8 The picture above shows the PICUS test carried out at 10 centimetres above ground level for T19 Common Lime. Analysis of PICUS Sonic Tomograms; T7 Silver Birch The tomogram was taken level with the fungal fruiting bodies evident on the North and North-East sides of the main stem. The results show that decayed/damaged wood occupies the central area of the tree at this height. Overall 32% of the cross-section is represented as solid wood, illustrated as brown on the PICUS image. 10% of the cross section was identified as being partially damaged which is illustrated as green on the PICUS image and 58% was identified as damaged or decayed wood, which is illustrated as violet and blue. The area of decayed wood (illustrated in the tomograph image as blue) is considered to be 41% of the total wood strength of the solid wood. The circumferential red line on the Tomogram indicates Mattheck s t/r ratio, (when a tree is two thirds or more hollow the probability of failure is high). It can be seen that the residual sound wood is generally insufficient to satisfy the ratio. The circumferential green line on the Tomogram indicates the Tree Stability Assessment included within the Picus Q72 software. When applying the dimensions of the tree, species and target value safety factor of 200% the green line depicts the maximum size of the cavity permitted with the remaining stability. Thus we can see that the residual wall is predominantly insufficient to extend beyond the green line. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 8 of 17

9 T12 Weeping Willow The tomogram was taken at approximately 120 centimetres above ground level at the height hollow sounds were noted during the initial tree survey. The results show that the tree contains no significant decay at this height. 100% of the cross-section is represented as solid wood, illustrated as brown on the PICUS image. 0% of the cross section was identified as being partially damaged (which is illustrated as green on the PICUS image), damaged or decayed wood (which is illustrated as violet and blue). T13 Weeping Willow The tomogram was taken at approximately 250 centimetres above ground level at the height hollow sounds were noted just below the historic pruning wound on the east side of the main stem in the initial tree survey. The results show that decayed/damaged wood occupies the central area of the main stem and extends out to the north-eastern side of the tree at this height. Overall 38% of the cross-section is represented as solid wood, illustrated as brown on the PICUS image. 11% of the cross section was identified as being partially damaged which is illustrated as green on the PICUS image and 51% was identified as damaged/ decayed wood which is illustrated as violet and blue. The area of decayed wood (illustrated in the tomograph image as blue) is considered to be 43% of the total wood strength of the solid wood. The circumferential red line on the Tomogram indicates Mattheck s T/r ratio, (when a tree is two thirds or more hollow the probability of failure is high). It can be seen that the residual sound wood is generally insufficient to satisfy the ratio. The circumferential green line on the Tomogram indicates the Tree Stability Assessment included within the Picus Q72 software. When applying the dimensions of the tree, species and target value safety factor of 200% the green line depicts the maximum size of the cavity permitted with the remaining stability. Thus we can see that the residual wall is predominantly at the boundaries or insufficient to extend beyond the green line. T18 Common Lime The tomogram was taken at approximately 15 centimetres above ground level at the height hollow sounds were noted on the North side of the main stem in the initial tree survey. The results show that decayed or damaged wood occupies the central area of the main stem and extends out to the north-eastern side of the tree at this height. Overall 41% of the cross-section is represented as solid wood, illustrated as brown on the PICUS image. 20% of the cross section was identified as being partially damaged which is illustrated as green on the PICUS image and 39% was identified as damaged/ decayed wood which is illustrated as violet and blue. The area of decayed wood (illustrated in the tomograph image as blue) is considered to be 49% of the total wood strength of the solid wood. The circumferential red line on the Tomogram indicates Mattheck s t/r ratio, (when a tree is two thirds or more hollow the probability of failure is high). It can be seen that the residual sound wood is generally insufficient to satisfy the ratio. The circumferential green line on the Tomogram indicates the Tree Stability Assessment included within the Picus Q72 software. When applying the dimensions of the tree, species and target value safety factor of 200% the green line depicts the maximum size of the cavity permitted with the remaining stability. Thus we can see that the residual wall is predominantly insufficient to extend beyond the green line. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 9 of 17

10 T19 Common Lime The tomogram was taken at approximately 10 centimetres above ground level at the height fungal fruiting body is attached and hollow sounds were noted on the north side of the main stem in the initial tree survey. The results show that decayed/ damaged wood occupies the northern area of the main stem, extending laterally into the central wood of the stem. Overall 52% of the cross-section is represented as solid wood, illustrated as brown on the PICUS image. 12% of the cross section was identified as being partially damaged which is illustrated as green on the PICUS image and 36% was identified as damaged/ decayed wood, which is illustrated as violet and blue. The area of decayed wood (illustrated in the tomograph image as blue) is considered to be 40% of the total wood strength of the solid wood. The circumferential red line on the Tomogram indicates Mattheck s t/r ratio, (when a tree is two thirds or more hollow the probability of failure is high). It can be seen that the residual sound wood is generally insufficient to satisfy the ratio. The circumferential green line on the Tomogram indicates the Tree Stability Assessment included within the Picus Q72 software. When applying the dimensions of the tree, species and target value safety factor of 200% the green line depicts the maximum size of the cavity permitted with the remaining stability. Thus we can see that the residual wall is predominantly at the border or sufficient to extend beyond the green line. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 10 of 17

11 Summary of the Visual Tree Assessment (VTA) component of the assessment; T7 Silver Birch The tree has average vigour, with deadwood up to 4 centimetres in diameter occupying less than 5% of the crown mass. The calculated live crown ratio (LCR) of the tree is 67%, which is considered to be adequate. The main stem of the tree from ground level to 3.0 metres leans to the North at an angle of approximately 10.0 degrees. The crown of the tree predominates to the North-East, possibly due to previous competition for available light. There are two Heterobasidion annosum fungal fruiting brackets attached to the base of the main stem on the North side of the tree. The exposed buttress roots on the north side of the main stem sound hollow when struck with a mallet. The hollow sound extends from ground level to approximately 0.5 metres above ground level. There are a large number of target cankers throughout the tree crown. No excavations were carried out in the root zone of the tree. T12 Weeping Willow The tree has average vigour, with deadwood up to 4 centimetres in diameter occupying less than 5% of the crown mass. The calculated live crown ratio (LCR) of the tree is 88%, which is considered to be adequate. There is decay evident on the top-side of exposed roots to the North-West of the tree. 2 fungal fruiting bodies, potentially Daedaleopsis confragosa were noted in the crown of the tree at the points of old pruning wounds. One dark coloured specimen to the east targeting the bank of the duck pond and a discoloured desiccated specimen to the west of the tree s crown at a height of between 3.5 to 4.0 metres. A hazard beam was noted at 3.5 metres above ground level in the crown on the West side of the tree s main stem. No excavations were carried out in the root zone of the tree. Exposed sections of buttress roots appear sound when struck with a mallet. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 11 of 17

12 T13 Weeping Willow The tree has average vigour, with dead wood occupying approximately 5% of the crown volume up to 9cm in diameter. The calculated live crown ratio (LCR) of the tree is 78%, which is considered to be adequate. There is decay evident on the top side of exposed roots to the South of the tree. The tree has previously been heavily reduced and there is an historic pruning wound at 2.5 metres above ground level on the east side of the tree. There is visible decay at the point of the old wound and dark exudation extending to the ground. Hollow sounds were noted at an area 1.8 metres wide from the point of the wound, extending down to 1.5 metres above ground level. No excavations were carried out in the root zone of the tree. Exposed sections of buttress roots appear sound when struck with a mallet. T18 Common Lime The tree has average vigour, with dead wood up to 10cm occupying less than 5% of the crown volume. The calculated live crown ratio (LCR) of the tree is 82.5%, which is considered to be adequate. Hollow sounds were noted at the base of the tree when tapped with a mallet. The tree has been historically pollarded at 5.0 metres and has since been allow to lapse. There are approximately ten limbs extending the height of the tree from the old pollard point. There is decay evident at the old pollard points and weak attachment points formed at the new growth. No excavations were carried out in the root zone of the tree. T19 Common Lime The tree has average vigour, No deadwood was noted in the tree s crown. The calculated live crown ratio (LCR) of the tree is 62.5%, which is considered to be adequate. There is a Ganoderma applanatum fungal fruiting body attached to the main stem of the tree at ground level on the north side. The surrounding area sounds hollow when tapped with a mallet. Minor decay was noted on the exposed buttress roots to the South and south-west of the tree s main stem. It is likely this is as a result of strimmer damage. The tree has been pollarded at 5.0 metres above ground level, with 3 metres of regrowth from the pollard points. Decay is evident at these points. No excavations were carried out in the root zone of the tree. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 12 of 17

13 SOIL TESTS Soil tests were not deemed necessary for this particular project. RESULTS OF SOIL AND ph SAMPLE TESTS Soil tests were not carried out. ph tests were not carried out. FLUORIMETER TESTS A fluorimeter test evaluates the ability of the chlorophyll in tree leaves to turn sunlight into energy (sugars). The physiological condition of a tree and, to some degree, its life expectancy can be assessed. This measure can prove scientific, non-bias measurement to assist in making tree retention decisions on development sites. Fluorimeter tests were not deemed necessary on this occasion. FUNGAL, DISEASE OR INSECT, PATHOGENS Fruiting brackets of the decay fungus Heterobasidion annosum are attached to the base of the main stem of T7 Silver Birch. Birch is one of the most common hosts of Heterobasidion annosum and this decay fungus causes a selective de-lignified white rot that starts in the root system. It is reported that the decay causes ductile fracture at the affected part of the tree ( Principles of Tree Hazard Assessment and Management Lonsdale. D, 1999, The Stationery Office, London.). A fruiting bracket of the decay fungus Ganoderma applanatum is attached to the main stem of the T19 Common Lime. This decay fungus causes a white rot that seems to start in the inner part of the root system and can form a central cone-shaped zone of decay (Lonsdale. D, 1999). Fungal decay brackets considered most likely to be that of Daedaleopsis confragosa were noted attached to old pruning wounds in the crown of T12 Weeping Willow. This fungi is saprophytic, usually confined to parts of a tree that have previously died or been seriously damaged from other causes (Lonsdale. D, 1999). The photograph above shows the exposed buttress roots of T7 Silver Birch and the arrows indicate the location of the fungal fruiting bodies of Heterobasidion annosum. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 13 of 17

14 The photograph above shows the Ganoderma applanatum decay fungal bracket attached to the base of the main stem of T19 Common Lime. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 14 of 17

15 CONCLUSION We conclude that the structure of T7 Silver Birch has been severely compromised by the fungal activity. As such the tree is considered to pose a high risk. The fungus remains active and the further spread of the decay into the main stem and buttress roots is highly probable. It should be noted that the tree is located in a high use area with a footpath running under the crown to the north and the main stem of the tree leans to the north at an angle of approximately 10 degree, further predisposing the tree to failure at the base. Crown reduction is not considered an option with this specimen due to the poor compartmentalizing ability of Birch trees. The PICUS test has indicated that there is no significant decay within the stem of T12 Weeping Willow at 120 centimetres above ground level. T12 is currently considered a Low Risk. A consideration for this tree will be the loss of shelter once the crown of T13 has been reduced. T12 will then potentially be exposed to wind forces that it has not grown to accommodate. This will increase the potential for branch failure in the crown of the tree. Because of the high target area that it occupies removal of a weak limb and a climbing inspection to check structural integrity is recommended. The PICUS test on T13 has indicated that decayed/damaged wood occupies the central and Eastern area of the tree at 250 centimeters above ground level. The structure of T13 has been significantly compromised at this height. 11% of the remaining wood is partially affected, indicating that the decay is still likely spreading through the tree at this height. T13 is in a high target area and poses a Moderate to High Risk to people and property within the crown of the tree. It is important that the weight and windsail area of the crown is significantly reduced for this tree in order to reduce the chance of failure at the area of decay in the main stem. T13 will produce substantial re-growth following the crown reduction and it is important that the tree receives on-going monitoring to ensure that the risk posed by the tree remains acceptable. The PICUS test has revealed decayed/damaged wood at the base of T18 Common Lime, as suspected during the initial visual assessment. Decayed/damaged wood currently occupies the central wood and extends to the North and Eastern areas of the main stem at 15 centimeters above ground level. The previous management of the tree as a pollard has lapsed and resulted in substantial new growth formed at weak attachment points with the main stem of the tree. There is potential for failure at these points, especially during high winds. In light of this it is important that the tree s wind-sail area is substantially reduced in order to reduce the chance of failure at the old pollard points or windsnap/windthrow from the base/rootplate of the tree. The structure of the main stem of T19 Common Lime has been compromised by fungal activity but the extent of decay is not currently significant. The ratio of sound to decayed/damaged wood is considered sufficient as the crown is compact as a result of recent pollarding. Future management of this tree with T178 as a pollard is recommended. It should be noted that fungus remains active in the tree and the removal of the leaf bearing crown will result in a temporarily reduced ability to put down new wood to combat the spread of the fungus. Therefore future monitoring is essential to ensuring that the tree remains at an acceptable level of risk. * Interpretations of Risk (As per Smiley, Fraedrich and Hendrickson 2009) Critical Risk Failure imminent: personal injury and/or property inevitable. High Risk Failure likely especially during storms: personal injury and/or property damage likely. Moderate Risk Failure possible especially during severe storms: personal injury and/or property damage possible. Low Risk Failure unlikely: personal injury and/or property damage unlikely. ** Dismantling/surgery risk Weakened crown anchor points possible, require full risk assessment prior to tree works F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 15 of 17

16 RECOMMENDATIONS REMEDIAL WORKS Recommendations Priority T7 Silver Birch Fell to ground level, grind stump out and replace with a new advanced nursery stock tree. Within 3 months. T12 Weeping Willow Current Recommendations Pollard at a terminal height of between 4.0 and 6.0 metres above ground level. Future Recommendations Re-pollard Within one year Every 3 to 5 years. T13 Weeping Willow Current Recommendations Reduce lateral to north-west with hazard beam by 4.0 metres in crown spread and at the same time carry out climbing inspection to check structural integrity of the tree. Future Recommendations Visual re-inspection Within one month Annually T18 Common Lime Current Recommendations Pollard at a height of 4.5 to 5.0 metres, pruning back to the nearest viable secondary growth point. Future Recommendations Re-pollard Within 6 months Every 3 to 5 years. T19 Common Lime Current Recommendations Re-pollard at a height of 5.0 metres. Future Recommendations Re-pollard every 3 to 5 years. Within 2 years. Every 3 to 5 years. F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 16 of 17

17 REPORT CLASSIFICATION: Tree Health & Structural Integrity Report REPORT STATUS: Complete REPORT COMPLETED BY: REPORT PEER REVIEWED BY: Mr Jason Mills Arboricultural Consultant Mr Andrew S Potter BSc Hons (For) MICFor M.Arbor.A Chartered Arboriculturist Senior Arboricultural Consultant SIGNATURE:.... CONSULTANT..DATE: 23/10/2012 REPORT REVIEWED BY:.....SENIOR CONSULTANT DATE:29/10/2012 F. A Bartlett Tree Expert Co. Ltd Tree Health & Structural Integrity Report Page 17 of 17