City Of Kent, WA
The City of Kent, WA, contracted DRG for a Level 3 risk assessment on a historic Deodar cedar in Kaibara Park due to safety concerns from its westward lean and visible decay. DRG conducted resistance drilling at 13 sites to assess decay and stability, determining low risk of trunk failure.
Getting A Detailed Look
The City of Kent hired Davey Resource Group, Inc. (DRG) to perform a Level 3 risk assessment on a historic Deodar cedar tree in Kaibara Park. The tree had an observable lean to the west, endangering road and parked cars in the event of trunk failure. Decay pockets on the east side of the tree were visible and suspected when sounded with a mallet. The client had established through visual assessment (Level 2 risk assessment) that the tree had a high risk of trunk failure.
The tree is historic and prominent, so the city wanted to conduct a more detailed analysis. Therefore, DRG conducted resistance drilling at 13 locations around the tree to establish the extent of decay and identify places where the tree was at risk of mechanical failure based on declining wood strength. Measurements from the drill revealed acceptable levels of wood strength at critical locations. The Level 3 risk assessment indicated that trunk failure is improbable in the next three years and that the overall risk rating for this tree is Low.
Reducing Risk While Preserving History
DRG advised that the tree should be retained but visually inspected annually by an ISA Certified Arborist with Tree Risk Assessment Qualification and, in subsequent years, re-inspected with a resistance drill to monitor changes in wood strength. DRG also recommended that the city expand the park by removing parking stalls and pavement within striking distance of the tree. This expansion would also improve the growing conditions for this tree and other trees in the park.
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