Arborist Report - Talbot Mackenzie & Associates - March 14, 2013

Assignment

Provide arborist services to review the site conditions on the property as they existed on March 05, 2013 and as they relate to tree retention and protection issues. Review the recent encroachment into and impacts on the tree resource as outlined in the Town of View Royal's February 22, 2013 report prepared by the Town Planner. Determine the impacts that have been exerted on the tree resource and prepare a report outlining the impacts, and outline measures to reduce the impacts on the trees, where possible.

Findings and Potential Impacts

The potential areas of impact, as outlined in the above mentioned report, include:

1. Impacts on the root zones of the large Douglas-fir trees at the end of Anya Lane and shown to be located on a section of property that is attached to the adjacent property at 1700 Wilfert Road.
2. Impacts on the trees within the development permit area and related to the driveway grading within this area.
3. Impacts on the bylaw-protected Big Leaf maple trees growing below and to the east of the house footprint.

With the amount of fill soil that is presently on the site, it is difficult to determine if and to what depth any excavation that may have occurred has encroached into the soil layers and the root zones, below the original site grade. The layer of fill soils have been placed within what we would consider to be the critical root zone areas of several trees in the development permit area and the bylaw-protected Big Leaf maple trees. At present, there is no visible evidence that the large structural supporting roots have been severed, and we did not observe any soil cracking, heaving, root pate lifting, unnatural trunk leans or any other indicators of root instability.

Injury to a 15 cm diameter root that extends from the 125 cm diameter Douglas-fir tree (at the end of Anya Lane on the 1700 Wilfert Road property) was observed, but it does not appear that this root has been severed. Fill soil has been placed over the root zones of a 35 cm and a 53 cm diameter Douglas-fir, and boulders have been placed against the trunk of, and fill soil placed within, the root zone of a 41 cm Big Leaf maple located within the development permit area.

We observed four multiple stemmed bylaw-protected Big Leaf maple trees on the bank below the house footprint. After viewing the plan contained in the Environmental Review, it appears that at least one and possibly two Big Leaf maple trees have been removed. Mechanical injury is visible on the trunks and stems of all of the maple trees; however, the injury that is visible above the level of fill soil appears relatively minor. A deep layer of fill soil has been placed within the critical root zones of the Big Leaf maple trees, both above and below the tree trunks. While this species of tree is relatively tolerant to construction impacts related to loss of roots that are not within the root plate radius, they are not tolerant to fill soil being placed around their trunks or within their critical root zone areas.

Mitigation of Impacts

We recommend the following procedures be implemented, to reduce the impacts on the trees to be retained.

While there were no visible indicators of root instability observed during our site visit, it is difficult to tell, due to the amount of fill soil present, whether any root structures have been severed. In the short term, we recommend monitoring the trees during high wind events for any evidence of soil, lower trunk or root plate movement.

At present, the backfill soils that have been placed over the root systems and driveway area are protecting the root structures in the native soil layers that are beneath these fill soils; however, to have a reasonable expectation that the trees to be retained will survive long term, it will be necessary to remove these fill soils from around their base.

We recommend the following:

1. Once the backfill of the foundation around the building footprint has been completed and machine activity is no longer required, the fill soils above the maple trees and below the maple trees should be removed to the original site grade that was present prior to the placement of these soils. a. An area extending out one metre from the trunk of each tree must be excavated by hand to determine the level of the original grade and to prevent damage to the tree root collars. b. The fill soil should be removed to the edge of the branch drip zone or approximately 10 metres out from the base of the tree. c. If fill soil is to be retained outside the drip zone area at a higher grade than the root zone, a method of draining this area must be considered so that standing water does not accumulate in the tree root zones. d. To prevent further mechanical injury, protective barrier fencing or solid hording must be placed around and one metre out from the trunks of the trees that are to be retained, until the fill soil has been removed. e. If the fill soils are to be removed prior to completion of construction then the critical root zones of the trees should be isolated from the construction activity by erecting barrier fencing once the fill has been removed. f. All excavation to remove fill soils must be supervised by an ISA Certified Arborist.
2. An ISA Certified Arborist must also supervise the removal of fill soils from the driveway area that is within the development permit area. The fill soils should be retained until machine activity is no longer required within this area. If boulders are to be remain along the edge of this driveway, they must be carefully placed or relocated so that the boulders do not touch the trunks of the trees that are to be retained. A recently created footpath runs through the undisturbed area between the upper and lower areas of the property and between the driveway and the stream. This path should be decommissioned or a proper path that is covered in a deep layer of suitable mulch or similar material should be established, to prevent further soil compaction within this area. Alternately, this area could be isolated by erecting barrier fencing.
3. The injured root extending from the 125 cm Douglas-fir tree should be identified on site and protected from further injury. No further excavation should occur in this area and the removal of any fill soils must be supervised by an ISA Certified Arborist. The edge of the driveway should be fenced to prevent any further encroachment into this area.

Please do not hesitate to call us at 250-479-8733 should you have any further questions. Thank you.

Yours truly,

Tom Talbot & Graham Mackenzie ISA Certified, & Consulting Arborists

Disclosure Statement

Arborists are professionals who examine trees and use their training, knowledge and experience to recommend techniques and procedures that will improve the health and structure of individual trees or group of trees, or to mitigate associated risks. Trees are living organisms, whose health and structure change, and are influenced by age, continued growth, climate, weather conditions, and insect and disease pathogens. Indicators of structural weakness and disease are often hidden within the tree structure or beneath the ground. It is not possible for an arborist to identify every flaw or condition that could result in failure nor can he/she guarantee that the tree will remain healthy and free of risk. Remedial care and mitigation measures recommended are based on the visible and detectable indicators present at the time of the examination and cannot be guaranteed to alleviate all symptoms or to mitigate all risk posed.