SouthShore Forest Consultants. Arborist Report. For

Transcription

1 Arborist Report For 1957 Llewellyn Place District of North Saanich, B.C. December 10, 2016 Prepared for: Collyn & Rena Varnes Prepared by: Page 1

2 10163 Fifth Street, Sidney B.C., V8L 2Y2 Phone: (250) , RE: Arborist Tree Risk Assessment Background/Scope of Work was contacted by Collyn & Rena Varnes, and requested to assess four (4) trees which are located in the rear of their property located at 1957 Llewellyn Place in the District of North Saanich. The Varnes are concerned about the general liability to their property and have questioned the stability of the four (4) trees in the landscape. Each of the trees is protected under a covenant which had been created on their property. Furthermore each of the trees were positioned as a cohort trees contained in a mixed forest condition. Currently each tree has been exposed and would be considered as edge trees which have been newly exposed to environmental conditions. The client would like a Visual Tree Assessment (VTA) to be performed on each tree. Detailed observations would be provided in an Arborist Report. agreed to complete the assessment and provide the findings in an Arborist Report. Methodology On December 8th, 2016 the property was entered and a Tree Inventory and Assessment was conducted by. The weather that day was cool and clear, with wind gusts up to 40km. The temperature that day was approximately 0 celcius. The property and individual trees were visually assessed and no form of diagnostic tools or invasive techniques were used during the assessment. Excavation to expose sections of each trees root crown did occur. All tree measurements were made with the use of a standard metal forestry tape and Clinometer (height measurements). Measurements and observations were recorded with the intent to provide a static representation of the area. Photographs of the site were taken during the assessment and these are included as Appendix A of this report. During the assessment one (1) tree was identified and numbered with a metal tag. It was inventoried as #788. Three (3) trees have been previously inventoried and can be identified with a plastic yellow surveyors tag. Their tag numbers are # 423, #424 & #425. Each tag is located approximately 2 metres above grade along the stem of each tree. Page 2

3 Observations/Discussion During the site assessment we observed the construction of a new residential single family home which the client was constructing. We observed the remnants of a second growth coastal forest which had been removed to accommodate the development of three (3) residential lots. Each lot measuring approximately one half a hectare in size. Douglas-fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata) appeared to be the dominate tree species. During the assessment we observed grade increases in the south western portion of the property. Each of the subject trees is positioned in the upper portion of the rear yard. This section of the property will be landscaped and designed to provide a retaining wall to reduce erosion. We assume that the client will be required to grade, compact and cut soil grades to complete the landscape. When this occurs, root damage combined with changes to hydrological flows will occur. We believe that minor changes to each trees Protected Root Zone (PRZ) will negatively affect tree condition and sustainable root development. The newly created edge effect trees, trees which have been preserved on the edge of a newly exposed forest line, are more susceptible to failure due to forces which are related to tree size, position and reactionary forces when increased strain or tension is inflicted upon them. In this case the client is required to retain four trees which have increased in failure potential, due to the acceptance of a Demolition Permit and guidelines which allow for the removal trees on private property. The Tree Care Industry has devoted substantial time and experimental efforts into studying tree mechanics. The slenderness ratio, also called the height-todiameter ratio has been used as a guideline which some professional use when assessing risk factors for solitary trees which have become edge trees in newly exposed conditions. Under the current circumstances we believe that the client has a valid concern and we believe that the each of the four (4) protected trees have increased in the potential for failure on site. We believe that the retention of the trees would become a hardship to the client and neighbouring properties. Combined with the construction damages and landscaping concerns we believe that each of these four (4) trees can be mitigated through the planting of native trees which would acclimate to the new landscape conditions proposed for the site. A Cost to Cure methodology, would be somewhat accepted in this case. Not that the client would be expected to provide replacement trees for the size of each specimen. We would focus on immediate mitigation and provisions for the planting and maintenance of trees which would eventually provide tree populations in the protected treed covenant. Page 3

4 Inventory #425 Douglas-fir 66cm DSH (Diameter Standard Height) measured at 1.4m above grade 41m (height) 7m Protected Root Zone (PRZ) Fair/Fair Condition rating (health/structure) Tree Hazard Rating (2+4+4) =10 - Fail potential/size/target=hazard Rating 1 = No Hazard & 12 = Immediate Removal (High Hazard) Shifted root plate during stump removal project. Visible dead limbs in tree canopy. When we provide a height-to-diameter ratio evaluation this tree has a rating of The accepted threshold has been identified as In this case the tree is lower and would be considered to have a greater than normal failure potential in the current environment. #424 Douglas-fir 78cm DHS 42m (Height) 8m (PRZ) Fair/Fair Condition Rating Tree Hazard Rating (2+4+4) = 10 Two major surface root have been damaged. Crushing action, resulting to shear tearing and removal of outer cambium. Visible dead limbs in tree canopy. We have provided a height-todiameter ratio of In this case the tree has a 0.56 ratio, which is higher than the 0.50 threshold. In this case the tree would be considered to have a reasonable failure potential in the current environment. #423 Douglas-fir 76cm DSH 42cm (Height) 8m (PRZ) Fair/Fair Condition Rating Tree Hazard Rating (1+4+4) = 9 Damage to the tree upper root crown was identified during the assessment. Positioned in a root union with a cedar tree. Visible dead limbs in tree canopy. We have provided a height-todiameter ratio of In this case the tree has a 0.55 ratio, which is higher than the 0.50 threshold. In this case the tree would be considered to have a reasonable failure potential in the current environment. Page 4

5 #788 Western red cedar 89cm DSH 28m (height) 9m (PRZ) Fair/Fair Condition Rating Tree Hazard Rating (1+3+4) = 8 This is codominant tree with a lower attachment wedged between the primary stem and Douglas-fir # 423. The lower attachment had a hollow detected in it during the assessment. We have provided a height-to-diameter ratio of In this case the tree would be considered to have a lessened failure potential in the current environment. Recommendations Provide tree removal for tree # 423,424,425 & 788. Provide tree replacement to ensure that tree mitigation measures are met. Provide tree replacement at a ratio of 2:1. Ensure that all tree planting stock is no less that #15 gallon or B&B stock which is retained from a local commercial tree nursery. Michael Butcher BSc Forestry ISA-ON-0583A CTRA# 1401 Bill Plant Forest Technician, B.C. ATTACHMENTS: Appendix A Site Photos Page 5

6 Arborist Disclosure Statement: Arborist are tree specialists who use their education, training and experience to examine trees, recommend measures to enhance the beauty and health of trees, and attempt to reduce the risks. Arborist cannot detect every condition that could possibly lead to structural failure of a tree. Trees are living organisms that fail in ways we do not fully understand. Conditions are often hidden within trees and below the ground. Arborist cannot guarantee that the tree will be healthy and safe under all circumstances, or for a specific period of time. Trees are dynamic specimens, not static. Changes in conditions including the environment are unknown. Remedial treatments cannot be guaranteed. Trees can be managed, but they cannot be controlled. The only way to eliminate all risk is to eliminate all trees. Tree Assessment Condition Rating Good - Fair - Poor- Dead- A tree specimen which is exempt defects, branch dieback, moderate insect and fungal identification. This tree has evenly distributed branching, trunk development and flare. The root zone is undisturbed, leaf, bud and flower production and elongation are normal for its distribution. A tree specimen which has minor defects, branch dieback, previous limb failure, identification of cavities and insect, or fungal identification. This tree has multiple (2-3) primary stem attachments; previous utility pruning, callus growth and poor wound wood development. Minor root girdling, soil heave and identifiable mechanical damage to the root flare or root zone. A tree specimen where 30-40% of the canopy is identifiably dead, large dead primary branching, limited leaf production, bud development and stem elongation. Limb loss or failure, and heavy storm damage leading to uneven weight distribution. Large pockets of decay, multiple cavities, heavy insect and fungal infection. Root crown damage or mechanical severing of roots. Root plate shifting, heavy lean and movement of soil. Tree has been observed to be dead with no leaf, foliar and bud development. No stump sprouts and root suckers are present. Excavation Process and Recommendation for Tree Root Zones 1. Provide and schedule Project Arborist to assess site prior to construction. 2. Inventory and identify trees and hazards which could complicate excavation process. 3. Utilize hand tools and cutting equipment when large tree roots are anticipated. 4. Provide small rubberized track excavation equipment which will reduce soil compaction. Page 6

7 5. Excavator operator must be well informed about dig site and goal to complete project. 6. Use shallow excavation sweeps across the site to establish a depth which roots can be easily identified. (3cm to 5cm in depth of soil for each sweep across the soil face) 7. Roots greater than 10cm in diameter should be preserved and inspected by the Project Arborist. The project arborist will determine if roots should be pruned or cut. 8. All roots greater than 6cm in diameter should be identified and documented for project records. 9. Photos are highly recommended for documentation purposes. Assessment of the site may expose further tree issues or conditions. If this occurs the project arborist will contact District Staff for further recommendations. Page 7