Tree Risk Assessment

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Tree Risk AssessmentUnderstanding and addressing the risks associated with trees makes your property safer andreduces potential liability. Trees are an important part of our world. They offer a wide range ofbenefits to the environment and provide tremendous beauty. However, trees can also bedangerous. Trees and/or parts of trees may fail and cause significant injury to people and/orproperty damage, so sometimes it’s important to assess and manage trees for risk.Anyone can assess a tree for risk, the question you must ask yourself is, are they qualified andappropriately insured to do so?RTS performs tree risk assessment in accordance with ANSI A300 (Part 9) - Tree RiskAssessment. Not only because we must as ISA Certified Arborists who are Tree RiskAssessment Qualified (TRAQ), but also because it ensures consistency by providing astandardized and systematic process for assessing tree risk.Risk assessment via TRAQ methodology takes one of three levels, depending on the extent ofthe assessment desired (or needed) by the client.Level 1 – This is a limited visual assessment of an individual tree or population of trees. It can beperformed as a “drive-by” assessment in the case of many trees or even as a limitedassessment as might be performed during an estimating request. RTS typically does not chargefor this type of risk assessment. However, given its brief nature, a Level 1 assessment oftencomes with a high degree of uncertainty.Level 2 – More involved than a Level 1 assessment, this is a 360-degree visual evaluation of atree where the crown, trunk, root flare, above-ground roots, and site conditions are evaluatedwith regard to specific targets. It also may involve the use of simple tools (probe, inclinometermallet, etc.) and is typically carried out using the ISA Basic Tree Risk Assessment form.Level 3 – The most extensive type of assessment, this includes what’s done in a Level 2assessment and uses specialized tools and/or techniques. Aerial inspections, root flareexaminations, and/or decay detection/characterization through core resistance drilling (seemore below) are typical of this level of assessment.After the risk assessment has been conducted, RTS works with the client to explain the findingsand offer solutions. We understand that each client is unique and risk tolerance varies.Sometimes, removal may be warranted. However, in other cases, the risk can often be loweredto an acceptable level by employing risk mitigation. Often, this may take the form of installing asupplemental support system, pruning, and/or PHC measures to improve tree strength.Royce’s Tree Service / 828-768-2747 / estimate@roycestreeservice.com

Core Resistance DrillingRTS owns a special tool that most other tree companies don’t have due to its roughly fourthousand dollar cost – a core resistograph – specifically an IML F300. Used in Level 3assessments, the IML F300 can peer into the hidden, internal state of a tree’s core bymeasuring and recording drill resistance. Having this capability can remove the limitations thatoften come with simple, visual-based assessments.Royce’s Tree Service / 828-768-2747 / estimate@roycestreeservice.com

Purdue extensionFNR-475-WTree Risk ManagementAuthorLindsey Purcell,Urban Forestry Specialist,Purdue UniversityDepartment of Forestry &Natural Resourceswww.fnr.purdue.eduTrees provide many benefits for our homes, businessesand properties. If a tree is defective, however, it maybecome a hazard. It is important to understand thattree owners have a duty to inspect and maintain theirtrees. All property owners should take reasonablesteps to protect themselves by involving a qualifiedconsultant or certified arborist.The primary responsibilities of the arborist are toassess the potential for tree failure, advise ownersof the consequences of failure and recommendthe proper measures to prevent and abate failures.In assessing and managing trees it is important tocreate a balance between the inherent risk a treeposes and the benefits provided by the tree. Risk treemanagement begins with these basic steps:reduce tree liabilities: The property owner ormanager has an obligation to periodically inspecttrees for unsafe conditions. Since all trees have riskassociated with them, regular inspection compelsthe owner or manager to evaluate the amount of riskthey are willing to assume. Tree risk assessment is animportant part of a program to determine if a treeis structurally sound or has the potential for failure.Inspections show that the tree owner is activelymanaging their trees and could reduce the owner’sliability if a failure occurs.Unhealthy trees can fail, causing potential damage to nearby homes.

Tree Risk Management FNR-475-Winspect regularly: Trees should be assessed through inspectionsby a qualified arborist, preferably an International Society ofArboriculture Certified Arborist. Further inspections shouldbe conducted after major weather events. At a minimum, treesshould be inspected every five years or according to the owner’srisk tolerance.document and maintain records: Every inspection should berecorded and kept on file for future reference. These records areimportant for several reasons. Past evaluations can show how atree has changed in its health and structure over the years. Also,written assessments are beneficial in liability claims and courtcases. These written evaluations could minimize liability if afailure occurs and a claim is filed against the tree owner.around the tree. Risk mitigation requires a process of logicaloptions focusing on protecting the target and preserving the tree.schedule tree work: While evaluating trees for risk, the inspectorshould note any tree maintenance needs. The inspection candetermine the timing and priority of work needed. The workshould be prioritized first for safety and then for tree health.Consider potential risk, activities around the tree, level ofacceptable risk and the needs of the client.Create good tree planting strategies: Identify planting needsand locations that become available as trees are removed ordestroyed. Improving the health and safety of the landscaperequires an understanding of management principles, such asspecies selection and diversity. Also consider the impact of siteinfrastructure, including utilities, streets and sidewalks, andchoose the right tree for the right place. Select trees knownto thrive under local conditions and sustainable as long-terminvestments in the property.Tree Risk AssessmentFor a tree to be considered hazardous it must be defective eitherin some part or as a whole, with risk for failure and a target thatis threatened. Trees are declared hazards if assessments havebeen completed and mitigation is required to prevent a failurefrom causing damage affecting the target. To understand theimplications of this concept, tree owners need to know somecommon terms of tree risk management.A target is people, property or activities that could be injured,damaged or disrupted by a tree failure. Tree owners mustcarefully assess the area around homes, playgrounds, sidewalksand parking areas. Is the target static, moveable or mobile?Consider whether people can be kept away or separated from thetarget area. Also, assess the target’s value and potential. Reviewthe target zone, which is the area where the tree or a branch islikely to strike when it falls, to determine consequences of thetree’s failure. The target zone should include the areas inside acircle around the tree, which is at least as wide as the total treeheight.Inspect trees for health conditions and defects during the tree risk assessment.develop a site policy and care plan: Every property managershould create and implement a policy for tree risk. Thisincludes developing a standard of care, an inspection processand mitigation of property risk. Routine care and scheduledmaintenance for all trees is essential.Mitigate tree risk: Tree owners should make every effort toreduce risk with proper pruning and health care practices.Consider all options before deciding on removal. If possible,move or remove the “target” (see definition in “Tree RiskAssessment” section). Install structural support systems wherefeasible. Modify site conditions to improve the environmentIdentify potential targets for tree failure.2

Tree Risk Management FNR-475-Wrisk is the combination of the likelihood of a tree failure eventand the severity of the possible consequences of that event.Every tree has the potential to fail; however, only a small numberof failures actually cause injury or damage. It is impossible tomaintain trees free of risk. Some level of risk must be accepted bythe owner.Hazard is a likely source of harm and is identified as the treepart or parts which will affect the target zone. For example, anentire tree or a single branch could be determined as a hazard.Hazards are identified during tree assessments, and tree ownersare required to take steps to minimize the risk of damage fromfailure.Individual tree characteristics must be considered whenconducting evaluations for defects and failure potential.Evaluations should take a systematic approach, assessing thepotential for tree failure, understanding the impact of suchfailures and outlining a plan of action to prevent and mitigatethese failures. Tree owners should fully understand the sitefactors and characteristics of the tree species. There are severalcontingencies that influence tree failure potential and risk. Theseinclude soil type and saturation, wind exposure, pest damage,poor growing conditions and poor pruning practices such astopping.Among the characteristics to consider when conducting tree riskevaluations are:Tree InspectionsAssessments should include a thorough examination of eachsection of the tree. A systematic approach using standardizedevaluation methods aids the process. Review the canopy (crown),branches and root zone to check for signs of failure. Theseinclude: Dead, diseased, dying or broken branches. Thinning or poor canopy health. An unstable branching pattern, overextended or weaklyattached branches, or cracks in the stems. Cracks or decayed areas in the main trunk. Exposed or decayed roots, heaving of the soil, fungus growth orcracks in the soil around the root plate.Recurrent inspections to determine tree health and conditionare critical for successful risk management programs. Trees inactive-use areas should be inspected annually for defects andconditions leading to failure. Inspections are necessary afterstorms to ensure excessive loads have not exceeded the strengthof the tree and its parts. Also, be sure to note trees with a historyof failures or those with problematic structure, for more frequentmonitoring and inspection. A good database and archive of treeevaluations is a critical strategy in the overall risk managementplan. Defects — severity and location. Decay, cankers, cracks andother positive indicators of weakness in the roots, stems andbranches may need immediate attention if a target is present. Species characteristics. Some tree species possess weaker wood,a susceptibility to decay, poor growth habits and potential forpests. They could be more likely to fail after wounding becauseof poor ability to wall off internal decay or health issues. Canopy size, shape and weight distribution. This is especiallytrue in situations where a tree is exposed to windy conditions, isleaning or has a poor stem-to-canopy ratio. Crown architecture. Poor branching and similar characteristicscan create high-risk situations in strong winds and otherweather conditions. Plant health and vigor. This determines how a tree canovercome wounding or pest infestations. The overall size of the defective part. A predetermined ratingsystem, which outlines critical thresholds, should be consideredand incorporated into the tree’s risk management plan.Purdue AgriCulture12/12It is the policy of the Purdue University Cooperative Extension Service that all persons have equal opportunity and access to its educational programs, services, activities, and facilitieswithout regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran.Purdue University is an Affirmative Action institution. This material may be available in alternative formats.Order or download materials fromPurdue Extension The Education Storewww.the-education-store.com3

RTS performs tree risk assessment in accordance with ANSI A300 (Part 9) - Tree Risk Assessment. Not only because we must as ISA Certified Arborists who are Tree Risk Assessment Qualified (TRAQ), but also because it ensures consistency by providing a standardized and systematic process for assessing tree risk. Risk assessment via TRAQ methodology takes one of three levels, depending on the .

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