Arboriculture: Dr. Shigo and ANSI A300
Overview
All line clearance employees need to understand basic arboriculture terms, techniques and principles for trimming trees near electric utility power lines and there are multiple ways to learn about Arboriculture. Some key principles for line clearance employees are covered by Dr. Shigo, ANSI A300 and ANSI Z133.1. We will explore all of these sources of information on arboriculture within this section.
Dr. Alex L. Shigo has published a great field pocket guide, Pruning Trees Near Electric Utility Lines, written for qualified line clearance tree trim employees. The basic concepts of tree trimming as recommended by Dr. Shigo are based on arboriculture fundamentals that are supported by utility foresters across the United States.
Plan Before You Plant and Plant the Right Tree in the Right Place
As you can tell across the landscape in an around utility power lines, some cities are better at arboriculture and tree planning than others. In many neighborhoods for example, there are maples and oaks growing in and around the power lines. This quite frankly is poor planning. The key premise here is that it is better for the city and the neighborhood to plant the right tree in the right place. In the area of the power lines this means that low growing, compact-form varieties should be planted that do not grow into the power lines. This eliminates the need for trimming and during storms will not potentially cause the severe hazard of downed power lines from tall trees falling on the power lines. Electricity from downed power lines can Kill!
Know and Practice ANSI and OSHA Standards
All line clearance employees need to be familiar with more than Dr. Shigo’s Pruning Trees Near Utility Lines. All line clearance employees are required to be familiar with ANSI Z133.1 and OSHA A300 (part 1) Pruning and (part 9) Tree Risk Assessment
Simple fundamentals for all line clearance employees to live by:
• Seek permanent solutions where possible, plant the appropriate tree near power lines, if you are not planting the trees, then spread the word about how important this is to the long-term stability of the community.
• Prune trees near power lines during regular pruning cycles (every 5 years or shorter)
• Remove branches ONLY at nodes
• Do not use Topping and tipping of trees, this only promotes excessive sprouting and regrowth.
• Do not remove branch collars or leave long stubs, this is a major cause of rot and tree branch or trunk failure.
• Do not paint cuts, wound dressing such as painting does not stop rot.
Tree Cutting Techniques
Cut trees at nodes, where branches meet the trunk. Do not cut trees between nodes or on the branch as this can lead to excessive sprouting, cracks or rot. Cutting at the node will help promote tree health. For large branch removal, use the 1, 2, 3 step technique:
Step 1 - undercut the branch by 1/3 but no more than ½. This will prevent bark stripping when the full cut is made.
Step 2 – cut the branch a few inches from the undercut in an overcut all the way through the branch.
Step 3 – now make the final cut at the node of the tree right outside the bark collar.
Cut with Care Principles
These are safety principles that all line clearance employees should follow:
• Wear the appropriate Personal Protective Equipment (PPE) at all times
• Know where your crew team partners are at all times when trimming trees
• Do not work when you are tired or sick
• Do not ignore cuts and bruises
• Report all incidents, because sharing incidents will prevent injury and save lives
• Plan your work, don’t “just do it”
• Respect power tools and use them safely
• Check tools and equipment before you go into the tree
• Do ONLY what you have been trained to do
• Concentrate on your job
• Have regular safety meetings
• Remove branches with care, using ropes when necessary
• Treat all conductors as ENERGIZED
• Do not force power tools beyond the limits
Remove Dead Wood Correctly
Removing dead wood branches is a health treatment for trees, because rot-causing fungus can spread from the dead branch to the trunk of the tree. Cut dead branches as close to the ring of living wood at the node, but do not injure or remove the rink of living wood at the node. The tree’s defense system that blocks rot is in the living ring at the node.
Extreme Caution – Never Climb A Dead or Diseased Tree
Never climb a tree that is dead, diseased or has dead wood or dead branches. It is extremely dangerous as the tree limbs used for securing the climbers life support rope lines may break loose causing the climber to fall possibly to their death. Use a bucket truck or backyard bucket to trim or remove dead or diseased trees.
90 – 3 – 90 Concept
This is a concept that helps the line clearance tree trimmer understand a key principle.
1. 90% of the time
2. 3 branches can be cut to provide
3. 90% of the clearance
Three Orders of Pruning
The first order of pruning is to start pruning trees along power lines during regular pruning cycles. Make correct cuts the first-time older trees are pruned. The second order of pruning is when the tree receives some internodal cuts. Correct the incorrect cuts that were made the first time. It may be necessary to remove a complete branch to fix an incorrect cut. Third order pruning is when the tree receives many internodal cuts such as with topping or tipping or round overs. Pruning of many branches may be needed for these trees or remove the entire tree as it is severely damaged by previous incorrect cutting.
Recognize Cracks or Splits
Line clearance employees need to be able to identify tree branches that have splits or cracks in the branch as these branches are weak and prone to rot. It is best to remove the complete branch at the node when splits or cracks are identified.
Pruning Process Flow Chart
Pruning Systems
Pruning systems should be specified to achieve the desired long-term form of the plant. Consideration shall be given to the ability of the plant to respond to the selected pruning system. Pruning systems are defined as:
Natural – is a pruning system that should be preferred and will allow for changes in appearance per specified objectives without damaging the plant. The natural pruning system is the recommended pruning system for line clearance work.
Pollarding – is a pruning system that should be selected for appropriate size, species and age of the tree. Pollarding is a method of pruning that keeps trees and shrubs smaller than they would naturally grow. It is normally started once a tree or shrub reaches a certain height, and annual pollarding will restrict the plant to that height. Pollarding should not be performed on mature trees. Pollarded trees should be maintained as pollards. See diagram below for a summary of the before and after effect of Pollarding as a pruning technique:
Topiary – is a pruning system that should be used when the objective is a specified shape, such as a hedge or a row of arborvitae. Topiary is not a recommended pruning system for line clearance work unless it is part of a private owner’s decorative tree design in a backyard. Always notify the owner’s prior to trimming in their backyard and discuss the method of trimming planned such as topiary trimming if appropriate for the situation.
Pruning Cuts
Principles of correct pruning are defined below:
• The smallest diameter cut that meets the objective is preferred, avoid cross cuts.
• The cuts that expose the heart of the wood should be minimized.
• Branches may need to be pre-cut to avoid splitting or tearing the bark.
• When removing a branch, the final cut should be made outside the collar of living tissue.
• When removing a branch with included bark, the cut should be made from the outside and as close to the joint as possible.
• The final cut should leave the adjacent bark firmly attached.
• The interior and lower branches should be retained when consistent with the objective.
• When removing live branches, the majority of the cuts should be in the outer portion of the crown.
• A flush cut is not an acceptable practice as it cuts into the living collar or branch bark ridge.
• A reduction cut should be made at a node when trying to reduce a portion of the branch to a live lateral branch when it can be expected to sustain the remaining branch or stem.
• Heading cuts and shearing cuts should only be used when using the pollarding or topiary system and when the remaining laterals can sustain the remaining branches.
Pruning Practices
A qualified arborist should always:
• Perform a visual inspection of the tree to be cut, safety procedures, location, potential hazards and techniques to complete the work safely.
• Work practices should be in place the maintain the equipment and tools used for pruning. Work practices that damage the living plant beyond what is needed to obtain the objective should be avoided.
• Wound treatment should only be used when necessary to prevent the spread of pests or disease.
• Clearance prune only when necessary and should be reduced to lateral branches at the node. Tree removal may be necessary if clearance pruning is severe causing serious threat to the remaining portion of the tree.
• Perform mechanical pruning in rural or remote locations away from settled areas and dwellings.
• Consider topping as an unacceptable practice.
• Consider lion tailing of an interior lateral branch removal that results in a concentration of growth at the branch ends shall be considered unacceptable practice.
• Disposal of tree branch pruning debris should be planned ahead per applicable local, customer requirements. Repurposing of debris into firewood is preferable.
• A monitoring and pruning interval should be established based on the pruning system, health, species, location and growth rate of the plant.
Reference: ANSI A300 (part 1) Tree, Shrub and Other Woody Plant Management – Standard Practices (Pruning).
Tree Risk Assessment Flow Chart
Tree Risk Assessment should include but are not limited to:
• Objectives of the assessment clearly stated assessing the risk associated with tree failure or part of the tree, the potential for impacting and likely consequences
• Tree location and/or tree selection criteria
• Risk assessment methodology
• Level and details of the assessment, including tools, techniques used, time frame, etc.
• When the assessment will be conducted
• Type of report to be developed
• Due date of the report
Levels of Tree Risk Assessment
Level 1: Limited visual assessment – must specify trees, targets and unique conditions of concern (if any), the perspective of the assessment (ground, in vehicle, from airplane). If the severity of risk cannot be determined, then the assessor should recommend a Level 2 or 3 Assessment.
Level 2: Basic assessment – must specify trees, defect conditions that affect tree failure, loads on trees or tree parts, growth and site factors that may affect failure or impact, common hand tools should be used in the assessment. If the severity of risk cannot be determined, then the assessor should recommend a Level 3 Assessment
Level 3: Advanced assessment – should be done in conjunction with or following a Level 1 or 2 assessment, shall include assessment tools not available or included in assessment Level 2. The tools used shall be specified such as drilling, boring, sonic assessment, electrical resistance, radar, or radiation assessment, pull testing, root or soilassessment. (see Annex B – Common Advanced Tree Risk Assessment Techniques)
Tree Risk Analysis and Reporting
A Tree Risk Analysis Report shall include:
• Objective of the assessment
• Date of the inspection
• Identification of the assessors and their qualifications
• Identification of the location of the specified trees
• Part of the trees assessed
• A description of the methodology used
• Time frame for the assessment
• Tree risk assessment data collected
• Risk rating of the tree or tree parts
• Risk mitigation options and/or recommendation
• Recommendations for monitoring and follow-up
• Statement of the limitations of the assessment methodology
Reference: ANSI A300 (part 9) Tree, Shrub, and Other Woody Plant Management – Standard Practices (Tree Risk Assessment a. Tree Failure)
Overview
All line clearance employees need to understand basic arboriculture terms, techniques and principles for trimming trees near electric utility power lines and there are multiple ways to learn about Arboriculture. Some key principles for line clearance employees are covered by Dr. Shigo, ANSI A300 and ANSI Z133.1. We will explore all of these sources of information on arboriculture within this section.
Dr. Alex L. Shigo has published a great field pocket guide, Pruning Trees Near Electric Utility Lines, written for qualified line clearance tree trim employees. The basic concepts of tree trimming as recommended by Dr. Shigo are based on arboriculture fundamentals that are supported by utility foresters across the United States.
Plan Before You Plant and Plant the Right Tree in the Right Place
As you can tell across the landscape in an around utility power lines, some cities are better at arboriculture and tree planning than others. In many neighborhoods for example, there are maples and oaks growing in and around the power lines. This quite frankly is poor planning. The key premise here is that it is better for the city and the neighborhood to plant the right tree in the right place. In the area of the power lines this means that low growing, compact-form varieties should be planted that do not grow into the power lines. This eliminates the need for trimming and during storms will not potentially cause the severe hazard of downed power lines from tall trees falling on the power lines. Electricity from downed power lines can Kill!
Know and Practice ANSI and OSHA Standards
All line clearance employees need to be familiar with more than Dr. Shigo’s Pruning Trees Near Utility Lines. All line clearance employees are required to be familiar with ANSI Z133.1 and OSHA A300 (part 1) Pruning and (part 9) Tree Risk Assessment
Simple fundamentals for all line clearance employees to live by:
• Seek permanent solutions where possible, plant the appropriate tree near power lines, if you are not planting the trees, then spread the word about how important this is to the long-term stability of the community.
• Prune trees near power lines during regular pruning cycles (every 5 years or shorter)
• Remove branches ONLY at nodes
• Do not use Topping and tipping of trees, this only promotes excessive sprouting and regrowth.
• Do not remove branch collars or leave long stubs, this is a major cause of rot and tree branch or trunk failure.
• Do not paint cuts, wound dressing such as painting does not stop rot.
Tree Cutting Techniques
Cut trees at nodes, where branches meet the trunk. Do not cut trees between nodes or on the branch as this can lead to excessive sprouting, cracks or rot. Cutting at the node will help promote tree health. For large branch removal, use the 1, 2, 3 step technique:
Step 1 - undercut the branch by 1/3 but no more than ½. This will prevent bark stripping when the full cut is made.
Step 2 – cut the branch a few inches from the undercut in an overcut all the way through the branch.
Step 3 – now make the final cut at the node of the tree right outside the bark collar.
Cut with Care Principles
These are safety principles that all line clearance employees should follow:
• Wear the appropriate Personal Protective Equipment (PPE) at all times
• Know where your crew team partners are at all times when trimming trees
• Do not work when you are tired or sick
• Do not ignore cuts and bruises
• Report all incidents, because sharing incidents will prevent injury and save lives
• Plan your work, don’t “just do it”
• Respect power tools and use them safely
• Check tools and equipment before you go into the tree
• Do ONLY what you have been trained to do
• Concentrate on your job
• Have regular safety meetings
• Remove branches with care, using ropes when necessary
• Treat all conductors as ENERGIZED
• Do not force power tools beyond the limits
Remove Dead Wood Correctly
Removing dead wood branches is a health treatment for trees, because rot-causing fungus can spread from the dead branch to the trunk of the tree. Cut dead branches as close to the ring of living wood at the node, but do not injure or remove the rink of living wood at the node. The tree’s defense system that blocks rot is in the living ring at the node.
Extreme Caution – Never Climb A Dead or Diseased Tree
Never climb a tree that is dead, diseased or has dead wood or dead branches. It is extremely dangerous as the tree limbs used for securing the climbers life support rope lines may break loose causing the climber to fall possibly to their death. Use a bucket truck or backyard bucket to trim or remove dead or diseased trees.
90 – 3 – 90 Concept
This is a concept that helps the line clearance tree trimmer understand a key principle.
1. 90% of the time
2. 3 branches can be cut to provide
3. 90% of the clearance
Three Orders of Pruning
The first order of pruning is to start pruning trees along power lines during regular pruning cycles. Make correct cuts the first-time older trees are pruned. The second order of pruning is when the tree receives some internodal cuts. Correct the incorrect cuts that were made the first time. It may be necessary to remove a complete branch to fix an incorrect cut. Third order pruning is when the tree receives many internodal cuts such as with topping or tipping or round overs. Pruning of many branches may be needed for these trees or remove the entire tree as it is severely damaged by previous incorrect cutting.
Recognize Cracks or Splits
Line clearance employees need to be able to identify tree branches that have splits or cracks in the branch as these branches are weak and prone to rot. It is best to remove the complete branch at the node when splits or cracks are identified.
Pruning Process Flow Chart
Pruning Systems
Pruning systems should be specified to achieve the desired long-term form of the plant. Consideration shall be given to the ability of the plant to respond to the selected pruning system. Pruning systems are defined as:
Natural – is a pruning system that should be preferred and will allow for changes in appearance per specified objectives without damaging the plant. The natural pruning system is the recommended pruning system for line clearance work.
Pollarding – is a pruning system that should be selected for appropriate size, species and age of the tree. Pollarding is a method of pruning that keeps trees and shrubs smaller than they would naturally grow. It is normally started once a tree or shrub reaches a certain height, and annual pollarding will restrict the plant to that height. Pollarding should not be performed on mature trees. Pollarded trees should be maintained as pollards. See diagram below for a summary of the before and after effect of Pollarding as a pruning technique:
Topiary – is a pruning system that should be used when the objective is a specified shape, such as a hedge or a row of arborvitae. Topiary is not a recommended pruning system for line clearance work unless it is part of a private owner’s decorative tree design in a backyard. Always notify the owner’s prior to trimming in their backyard and discuss the method of trimming planned such as topiary trimming if appropriate for the situation.
Pruning Cuts
Principles of correct pruning are defined below:
• The smallest diameter cut that meets the objective is preferred, avoid cross cuts.
• The cuts that expose the heart of the wood should be minimized.
• Branches may need to be pre-cut to avoid splitting or tearing the bark.
• When removing a branch, the final cut should be made outside the collar of living tissue.
• When removing a branch with included bark, the cut should be made from the outside and as close to the joint as possible.
• The final cut should leave the adjacent bark firmly attached.
• The interior and lower branches should be retained when consistent with the objective.
• When removing live branches, the majority of the cuts should be in the outer portion of the crown.
• A flush cut is not an acceptable practice as it cuts into the living collar or branch bark ridge.
• A reduction cut should be made at a node when trying to reduce a portion of the branch to a live lateral branch when it can be expected to sustain the remaining branch or stem.
• Heading cuts and shearing cuts should only be used when using the pollarding or topiary system and when the remaining laterals can sustain the remaining branches.
Pruning Practices
A qualified arborist should always:
• Perform a visual inspection of the tree to be cut, safety procedures, location, potential hazards and techniques to complete the work safely.
• Work practices should be in place the maintain the equipment and tools used for pruning. Work practices that damage the living plant beyond what is needed to obtain the objective should be avoided.
• Wound treatment should only be used when necessary to prevent the spread of pests or disease.
• Clearance prune only when necessary and should be reduced to lateral branches at the node. Tree removal may be necessary if clearance pruning is severe causing serious threat to the remaining portion of the tree.
• Perform mechanical pruning in rural or remote locations away from settled areas and dwellings.
• Consider topping as an unacceptable practice.
• Consider lion tailing of an interior lateral branch removal that results in a concentration of growth at the branch ends shall be considered unacceptable practice.
• Disposal of tree branch pruning debris should be planned ahead per applicable local, customer requirements. Repurposing of debris into firewood is preferable.
• A monitoring and pruning interval should be established based on the pruning system, health, species, location and growth rate of the plant.
Reference: ANSI A300 (part 1) Tree, Shrub and Other Woody Plant Management – Standard Practices (Pruning).
Tree Risk Assessment Flow Chart
Tree Risk Assessment should include but are not limited to:
• Objectives of the assessment clearly stated assessing the risk associated with tree failure or part of the tree, the potential for impacting and likely consequences
• Tree location and/or tree selection criteria
• Risk assessment methodology
• Level and details of the assessment, including tools, techniques used, time frame, etc.
• When the assessment will be conducted
• Type of report to be developed
• Due date of the report
Levels of Tree Risk Assessment
Level 1: Limited visual assessment – must specify trees, targets and unique conditions of concern (if any), the perspective of the assessment (ground, in vehicle, from airplane). If the severity of risk cannot be determined, then the assessor should recommend a Level 2 or 3 Assessment.
Level 2: Basic assessment – must specify trees, defect conditions that affect tree failure, loads on trees or tree parts, growth and site factors that may affect failure or impact, common hand tools should be used in the assessment. If the severity of risk cannot be determined, then the assessor should recommend a Level 3 Assessment
Level 3: Advanced assessment – should be done in conjunction with or following a Level 1 or 2 assessment, shall include assessment tools not available or included in assessment Level 2. The tools used shall be specified such as drilling, boring, sonic assessment, electrical resistance, radar, or radiation assessment, pull testing, root or soilassessment. (see Annex B – Common Advanced Tree Risk Assessment Techniques)
Tree Risk Analysis and Reporting
A Tree Risk Analysis Report shall include:
• Objective of the assessment
• Date of the inspection
• Identification of the assessors and their qualifications
• Identification of the location of the specified trees
• Part of the trees assessed
• A description of the methodology used
• Time frame for the assessment
• Tree risk assessment data collected
• Risk rating of the tree or tree parts
• Risk mitigation options and/or recommendation
• Recommendations for monitoring and follow-up
• Statement of the limitations of the assessment methodology
Reference: ANSI A300 (part 9) Tree, Shrub, and Other Woody Plant Management – Standard Practices (Tree Risk Assessment a. Tree Failure)
