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HomeMy WebLinkAboutTR_Arborist_Report_12109SE164St_20260306_v1 March 6th, 2026 Prepared by: David Bigelow ISA Certified Arborist Tree Risk Assessment Qualified PN-9725A Property Address: 12109 SE 164th St., Renton, WA 98058 (Parcel #142390-0010) Client: Mark Monsrud (206) 992-4247 | monsy2002@msn.com Date / Time: 3/6/2026 – 12:45 PM Tree ID: Tree No. 1 (Tree 10 on site map) Assessor: David Bigelow, ISA Certified Arborist & Tree Risk Assessor PN9725A Tools Used: Visual inspection Assessment Time Frame: Imminent Arborist’s Report The tree described below was evaluated to determine its current condition and the potential for risk to adjacent targets. Trees are living organisms and their health, vigor, and structural condition can change over time. This report reflects conditions at the time of assessment and the information recorded on the attached ISA Basic Tree Risk Assessment Form. 1. Scope of Work A basic tree risk assessment was performed for one Western red cedar located at 12109 SE 164th St., Renton. The purpose of this assessment was to document observed defects and site constraints, identify targets, and rate risk using the ISA matrices, with particular emphasis on documented conflict between roots and on-site infrastructure. 2. Summary Tree: Western red cedar (Thuja plicata) • DBH: 33.8 in • Height: ~75 ft • Crown spread: 38 ft • Live Crown Ratio (LCR): 45% Target: “12109 infrastructure (underground and foundational)” with occupancy constant • Roots: continued/ongoing damage associated with infrastructure conflict; likelihood noted as imminent for the root/infrastructure condition. • Crown/Trunk: multiple codominant leaders (four tops originating around ~25 ft), included bark, weak attachments, poor taper, and lean (3–4°) across multiple stems; likelihood recorded as probable for codominant stem failure. Risk ratings: • Target 1 – Roots / “Continued damage” → High • Target 1 – Codominant leaders / “Failure at union (x4)” → High Overall tree risk rating: High Mitigation option: Remove / replace Residual risk: None 3. Methodology This assessment follows the ISA Basic Tree Risk Assessment approach, evaluating: • Observed defects in crown, trunk, and roots/root collar • Site factors and load factors • Target presence and occupancy • Likelihood of failure, likelihood of impact, consequences, and resulting risk rating This assessment was performed via visual inspection as listed on the form. 4. Site Conditions and Load Factors Topography: Flat Site changes: Root cuts noted; described as mitigation of a large root impacting water/sewer pipe. Soil conditions: Limited volume; pavement over roots; 65–70 percent coverage. Prevailing wind direction: NE Load factors recorded: • Wind exposure: Full • Relative crown size: Medium • Crown density: Sparse; Interior branches: Few • Recent/expected change in load factors: removal operations paused; continuation of removal/replacement recommended. 5. Tree Health and Condition Vigor: Low Foliage: Normal 92.5%; Necrotic 7.5% 6. Defects and Conditions Affecting Likelihood of Failure Crown and Branches • Unbalanced crown; LCR 45% • Dead twigs/branches 5% overall • Removal operations paused; limited south-facing foliage • Codominant structure: several tops (4) originating at ~25 ft • Included bark; weak attachments • Crown condition of concern: codominant stems with limited mass dampening; weighted toward home • Crown load on defect: Significant; likelihood of failure: Probable; fall distance: 25 ft Trunk • Codominant stems; included bark; poor taper • Lean: 3–4°, noted as multiple stems, uncorrected due to competition • Response growth: Fair • Trunk condition of concern: codominant stem failure; part size 40–45 ft x 16–20 in diameter; fall distance 25 ft • Trunk load on defect: Significant; likelihood of failure: Probable Roots and Root Collar Recorded root conditions include: • Cut/damaged roots noted; distance from trunk 12 ft • Root condition of concern: root damage to infrastructure; part size 5 in diameter • Root load on defect: Significant; likelihood of failure: Imminent (for the infrastructure- damage scenario) • Roots causing upheaval and cracks in the patio. Subsequent water drainage towards house. 7. Risk Categorization (ISA Matrices) 1. Roots – “Continued damage” – High 2. Codominant leaders – “Failure at union (x4)” – High Overall tree risk rating: High 8. Recommendations Remove / replace • Tree assessed after removal operations were paused. • Root pruning or root block installation not feasible due to limited area; tree has outgrown its location. 9. Limits of Assessment This is a preliminary ISA basic assessment with no stated inspection limitations on the form. The evaluation is based on visible conditions and the information recorded at the time of assessment. Trees are dynamic; conditions may change with weather, site disturbance, and time. 10. Conclusion The Western red cedar at 12109 SE 164th St., Renton presents a High risk condition driven by (1) ongoing root-related infrastructure damage and (2) multiple codominant leaders with union failure concern (x4), in a constant-occupancy target setting. The recorded mitigation is remove/replace, with residual risk recorded as none following mitigation. This report does not address the safe working distances for energized conductors. Contractors should ensure compliance with all relevant safety regulations. 1 person at work in the US dies from electrocution an average of once every day. Limits of the Report Unless otherwise stated: 1. The information in this report covers only the items examined and reflects their condition at the time of inspection. 2. The inspection was limited to a visual examination of accessible items without further dissection, excavation, probing, or coring. Any loss or alteration of part of this report invalidates the entire document. There is no warranty or guarantee, expressed or implied, that the trees in question may not develop problems or deficiencies in the future. Respectfully submitted, David Bigelow 528 13th Street Snohomish, WA 98290 (206) 504-0355 dvdbigelow@gmail.com ISA Certified Arborist #PN9725A Tree Risk Assessment Qualified Site map for illustration purposes only Photo 1 Photo 2 Photo 3 Photo 4 Photo 5