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DRG used the following criteria and matrices,based on the International Society of Arboriculture Best Management Practices—Tree Risk Assessment,Second Edition (E.Thomas Smiley,Nelda Matheny,and Sharon Lilly 2017),to arrive at a risk rating. 1.Likelihood of Failure.Identies the most probable failure and rates the likelihood that structural defect(s)will result in failure based on observed current conditions. 2.Likelihood of Impacting a Target.The rate of occupancy of targets within the target zone and any factors that could aect the failed tree as it falls towards the target. 3.Consequences of Failure.The consequences of tree failure are based on the level of target and potential harm that may occur.Consequences can vary depending on the size of the defect,a distance of fall for the tree or limb,and any other factors that may protect a target from harm.Target values are subjective, but DRG statry to assess them from our client's perspective. As shown in the matrix below,the likelihood of failure and the likelihood of target determine the likelihood of tree failure impacting a target. Likelihood of Failure Likelihood of Impacting Target Very Low Low Medium High Imminent Unlikely Somewhat likely Likely Very likely Probable Unlikely Unlikely Somewhat likely Likely Possible Unlikely Unlikely Unlikely Somewhat likely Improbable Unlikely Unlikely Unlikely Unlikely DRG’s urban foresters estimate the risk rating by combining the likelihood of tree failure impacting a target and the consequences of failure in the matrix below.Risk ratings are Low,Moderate,High,and Extreme.A Low Risk tree poses a low overall level of risk.A Moderate Risk tree may pose some threat,particularly during storm events or unusual weather.A High Risk tree presents a high likelihood of tree or tree part failure,even during normal weather conditions.An Extreme Risk tree always poses a signicant risk and probability of failure. Likelihood of Failure Consequences Negligible Minor Significant Severe Very likely Low Moderate High Extreme Likely Low Moderate High High Somewhat likely Low Low Moderate Moderate Unlikely Low Low Low Low Even though trees may pose multiple risks at once,DRG assigns one risk rating to each tree during the inventory process.The risk rating serves only as a prioritization mechanism and is not a guarantee;Roseville must determine the level of acceptable risk. 8.Risk Assessment Complete—Starecord if they are not able to complete the assessment due to obstructions,safety concerns,or other unforeseen site conditions. 9.Overhead Utilities—For each tree or site,DRG records if overhead utilities are: a.Present and not conicting. Davey Resource Group Page 22