The District of North Vancouver

Transcription

1 The District of North Vancouver January 12, File: RFS TO: Susan Rogers & Gavin Joyce FROM: Ralph Nevill & Wayne Maskall SUBJECT: Inter River "Digger" Park - Arborist Report ASSIGNMENT This arborist report of hazardous trees in the Digger Park forest area of Inter River Park is in response from a request from the District of North Vancouver Fire Rescue Services following an incident where a hiker was struck by a falling tree top. As these trails are actively and heavily used by local residents, public safety and risk mitigation for the forest trails area are the focus of the report. Therefore this assessment only considers those trees deemed to be a hazard and provides recommendations for their remediation. This inspection and report of hazardous trees and recommended action is independent of any future plans for the area. BACKGROUND On November 25, 2017 Chad Laforet, Assistant Chief Operations for the District of North Vancouver Fire Rescue Services reported his staff responded to a resident who had been struck by a falling tree top in forested area of Inter River Park just north of the Fire Training Centre (see map). Fortunately the hiker was not seriously injured, but Assistant Chief Laforet noted that tree top appeared to be rotting and that the surrounding area should be investigated sooner than later (Photo 1, 2). This area of Inter River Park is referred to Digger Park forest by the local residents and tree work in this area is highly contentious (Photo 2) as a large portion of the area has been proposed for new sports field development which many oppose. Previous to this event, an arborist report was prepared in May of 2017 by Binne & Associates for the trees in this area as part of a preliminary study of the development potential in Inter River Park. However, as the report did not examine dead trees on the site it cannot be used as a reference for the present study.

2 TREE & SITE DETAILS The trees were examined November 26 and December 5, The 3.4 ha Digger Park forest area is bounded on the north and northwest by the Inter River Park Sports Field #1 parking lot, Lynn Creek to the west, the Fire Training Centre to the south, the Digger Park playground to the southeast and on the east by condominium developments along Premier Street (map). The forest is comprised of roughly year old, mature decadent bigleaf maples, alders, hemlocks and a few western red cedars and Sitka spruce. The area is often flooded in the winter due to heavy rains and high water table, but dries out in the summer due to the rocky soil conditions. The recent droughty summers have placed these trees under considerable stress. Map showing approximate location of failed tree and other hazard trees in the area.

3 METHODS For the purpose of this report each hazardous tree was assigned a reference number painted on the side of the tree in orange paint below a large orange dot for easy identification. Information collected for each tree included: tree number, species, the diameter measured at 1.3 metres above grade (D.B.H.), tree condition, priority rating (using DNV Tree Rating Work Schedule), tree prescription to be taken based on condition and priority as well as any observations. A summary of the observations is presented in Table 1 while the complete inventory is in the Appendix. OBSERVATIONS Species Common Name Average Condition No. for removal Tsuga heterophylla Western hemlock Dead 16 Thuja plicata Western Red Cedar Dead 1 Acer macrophylla Bigleaf maple Dead 3 Alnus rubra Red alder Dead 2 Total 22 Table 1. Summary of hazard tree observations Most of the trees were deemed to pose an imminent hazard and rated Priority 1 or 2 requiring immediate removal. Three dead trees were rated Priority 3 as these trees present only a moderate risk of failure. RECOMMENDATIONS Mitigation of all of the dead trees be taken as soon as reasonably possible before the commencement of the bird nesting season in March 1, Where feasible the hazard trees to be removed will be snagged for habitat. In conclusion, the remaining trees are recommended for retention and monitoring as there are no other imminent tree failure risks noted at this time.

4 APPENDIX: TREE INVENTORY Tree Size # Cm Species Condition Priority Action Comments Hemlock Dead P2 10m / make safe* Hemlock Dead P2 10m / make safe Hemlock Dead P2 10m / make safe Broken top (Photo 2) 4 40 Alder Dead P1 Remove Not safe to climb Hemlock Dead P2 10m / make safe Hemlock Dead P2 10m / make safe Hemlock Dead P2 10m / make safe BL Maple Dead P2 Remove Not safe to climb Hemlock Dead P2 10m / make safe Hemlock Dead P2 10m / make safe Hemlock Dead P2 10m / make safe WR Cedar Dead P3 5-6m / make safe Hemlock Dead P2 5-6m / make safe Adjacent to Fire Training Centre Adjacent to Fire Training Centre Hemlock Dead P2 10m / make safe Hemlock Dead P3 10m / make safe Hemlock Dead P3 10m / make safe Hemlock Dead P3 10m / make safe Hemlock Dead P3 10m / make safe Hemlock Dead P3 10m / make safe Maple Dead P3 Remove Not safe to climb Maple Dead P3 Remove Not safe to climb Alder Dead P3 Remove Not safe to climb *For safety reasons it is the tree fallers choice to snag the tree at the prescribed height or remove the tree.

5 Photo 1. Failed top from dead 75 cm hemlock tree.

6 Photo 2. Dead hemlock trees in Digger Park Forest.

7 Testing and Analysis: The assessment completed on the trees defined within this report, consisted of a visual and physical inspection from the ground and was based upon the principals of Visual Tree Assessments. No invasive tests, such as using a resistograph or increment borer, were used during the testing for this report. Assumptions and Limiting Conditions: 1. The information contained in this report covers only those items that were examined and reflect the condition of these items at the time of inspection. The inspection is limited to visual examination of accessible components without dissection, excavation or probing. There is no warranty or guarantee, expressed or implied, that problems or deficiencies of the trees or property in question may not arise in the future. 2. The opinions in this Report are given based upon observations made using generally accepted professional judgment, however, because trees and plants are living organisms and subject to change, damage and disease, the results, observations, recommendations, and analysis as set out in this Report are valid only as at the date any such testing, observations and analysis took place. No guarantee, warranty, representation or opinion is offered or made by the District of North Vancouver as to the length of the validity of the results, observations, recommendations and analysis contained within this Report. 3. Care has been taken to obtain all information from reliable sources. All data has been verified insofar as possible; however, the appraiser/company can neither guarantee nor be responsible for the accuracy of information provided by others. 4. All tree work is to be completed under the supervision of an ISA Certified Arborist and in compliance with ISA, BC Hydro and WCB standards. 5. Alteration of any part of this report invalidates the entire report. If you have any questions or concerns please feel free to contact me. Ralph Nevill, PAg, RPBio, Certified Arborist The District of North Vancouver 355 West Queens, North Vancouver BC V7N 4N5 (604)

8 Tree Rating Work Schedule Priority 1 Sent immediately to arboriculture crew or prime contractor for mitigation Priority 2 Sent to the arboriculture crew or prime contractor to be mitigated through the next monthly tree work contract. Priority 3 Sent to the arboriculture crew or prime contractor to be mitigated through the next or subsequent monthly tree work contract as the workload allows. Priority 4 Sent to the Parks Department for consideration. Work may be deferred due to work load and /or budget considerations. Priority 5 Sent to Parks Department for consideration. Work may be deferred due to work load and /or budget considerations.

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