Isa training tree risk assessment & cabling bracing

Tree Assessment and Tree Assessment and Risk ManagementRisk Management

Certified Arborist Training

TREES HAVE VALUE!!

Benefits of Urban Trees:

Energy Savings

Property Value

Shade

Air Quality

Aesthetics

Quality of Life

Urban Wildlife

Tree AssessmentTree Assessmentand Risk Managementand Risk Management

What are the 3 types of pruning cuts?

Outline

Risk and Liability

Basic Tree Biology – Review

Identifying Hazard Trees

Mitigation

The value comes at a “price”, however.

There are risks associated when trees are in areas used by people and their “things” (targets).

Risk assessment includes the potential of a tree to fall, the environment that may contribute to its failure, and the potential target.

Evaluating trees for their potential to fail is a component of risk management.


TREES HAVE VALUE!!

TORT LAW – A “tort” is a civil wrong; more commonly stated, a non-criminal harm (wrong) done to persons or property. Tort can result from an intentional act (assault, battery, libel) OR may be unintentional (e.g., negligence)

NEGLIGENCE – A person is negligent when he or she fails to act as a reasonably prudent person under the circumstances.

Ignorance or stupidity are not excuses for dangerous or inappropriate behavior.


RISK AND LIABILITY

“Duty of Care” (Reasonable Person)

The current trend in the United States is that the landowner will be held to a “duty of care”, determined by the principles of negligence. A landowner is not only held to the duty of common prudence in maintaining trees on his property, but is also held to an even greater duty of inspection to discover possible defects of a tree in order to prevent it from falling and injuring others. If risk can’t be eliminated, it should be mitigated so that acceptable level of risk is achieved.

Some state have “recreational user statutes” that may exempt a landowner from liability.


RISK AND LIABILITY

Degree of Care Owed to Classes of Visitors

• INVITEE: This is the highest standard imposed on landowners by law. A landowner must make reasonable inspections of the premises to discover dangerous conditions and repair or warn of such dangers.

• LICENSEE: The duty here is limited to acting with ordinary care and to warn of dangerous concealed conditions that the landowner knows about.

• TRESPASSER: This is the lowest duty of care owed by a landowner. The only duty here is to not intentionally harm or set traps; there is no duty to warn of hazards.


RISK AND LIABILITY

Outline

Risk and Liability



Mitigation

Basic Tree Biology

90-95% of a Tree’s Root System is located in the Top 3 Feet of Soil!

3 ft 1 ft

Even though the tree may be left standing (for now) major trauma to these roots will kill the tree!

Roots can grow to twice the height!


50% of a Tree’s Root System is located in the Top 1 Foot of Soil!!!!

These are mostly the absorbing roots that provide WATER and NUTRIENTS

Critical Root Zone (CRZ)

The CRZ is typically the minimum area required to maintain the tree’s health and structural integrity.

The CRZ encompasses all tree roots out to at least the drip line of a tree.


Basic Tree Biology

As a general rule, the Critical Root Zone should extend at least to the drip line of a tree.

If the CRZ cannot be protected…

Disturbance may come as close as 5X the diameter of the protected tree on ONLY ONE SIDE!!

5X…then protect the rest!!


Outline

Risk and Liability



Hazard Tree Formula

Tools

Signs & Symptoms

Mitigation

Trees grow as if they are actually trees within a tree. Each year’s growth covers and surrounds the previous year’s tissue.

If a wound occurs, the tree responds by trying to wall off, or compartmentalize, the wounded area. The tissue from each new year of growth will cover the old wound and remain unaffected, as long as rot or decay does not move into the new tissue. If compartmentalization is effective, the new tissue remains healthy and the old wound is “walled off” or sealed behind the new tissue. (e.g., a hollow tree with sound wood around the hollow.)


Tree Wounding

A tree with structural defects likely to cause failure of all or part of the tree, which could strike a target.


Hazard Tree

Approaching the inspection:

Past history of the tree

Assess current health

Owners motives?

Litigation potential?

90% of all defects can be identified by a novice!!


Inspections

Performing the inspection:

Professional conduct

Use scientific methodology

Will a written report be required?

Will the report be a “note” on scrap paper or a five-page report with photos, etc.


Inspections

Hazard Tree Report Forms

There are several… Most are very detailed and require calculation of a “Hazard Rating” or Hazard Potential.


Inspections

Tree Risk AssessmentTree Risk Assessment

Hazard Tree Report Forms

There are several… Most are very detailed and require calculation of a “Hazard Rating”

Failure + Size + Target = Hazard Potential of part Rating Rating Each part of the formula is assigned a value of 1 through 4.

The total Hazard Rating can range from 3 to 12.


Inspections

Failure + Size + Target = Hazard Potential of part Rating Rating

1 = Low (Minor defects)

2 = Medium (Small to medium cavities within safe limits)

3 = High (Significant defects, serious stem decay)

4 = Severe (Cavity at or beyond safe limits, multiple defects, large dead branches or trees)



1 = <6” diameter

2 = 6-18” diameter

3 = 18-30” diameter

4 = >30” diameter



1 = Occasional Use (alley)

2 = Intermittent Use (side street)

3 = Frequent Use (main road)

4 = Constant Use (house)


What is the Hazard Tree Rating for this tree?


Tools of the Trade…..

Rubber mallet

Drill (standard or resistograph)

Increment borer

Binoculars

Ruler

Common sense


Inspections

Arborsonic Decay Detector

Dead wood

Cracks

Weak branch unions

Decay

Cankers , conks , fruiting bodies

Root problems

Poor tree architecture (structural defects)


Hazard Types

What 3 parts make up the ISA hazard formula?

NOT NEGOTIABLE!

Dead wood is unpredictable and should be removed as soon as possible.

Dead wood is brittle.

Dead Wood


A separation of the wood, a fissure or deep split in the bark and wood.


Cracks

HIGH FAILURE POTENTIAL

A crack goes completely through the stem or branch.

Stem has two cracks on the same segment with a cavity or extensive decay.

Stem has crack with another defect (lean, weak branch, etc.).

A fork in the stem or union of two or more main branches.

Co-dominant stems…

U-SHAPED V-SHAPED


Weak Branch Unions

HIGH FAILURE POTENTIAL

A weak branch union that is also cracked or decayed.

A weak union in a tree’s hot spot.


Weak Branch Unions

MODERATE FAILURE POTENTIAL

A weak union with included bark at the branch bark ridge


Weak Branch Unions

Wood that is rotted or missing (visible cavities).

Decay always results in less structural strength and stability.


Decay

Injury occurs.Fungi enters the wound and begins to discolor the wood as rot begins.

As years pass, the rot column grows in height, but is also covered by new layers of wood from each years new “ring” (tree in a tree).

The process continues.After many years of growth, the result is a visible trunk wound with an internal rot column behind it.


Decay

Internal Hollow

Exposed Cavity


If shell thickness is less than 1/3 of the stem radius, then the tree is unsafe.


An area of dead bark and cambium anywhere on the tree, often affecting the wood beneath it.


Cankers

Problems serious enough to warrant correction are partial windthrow (leaning with mounding, missing roots, and extensive root rot.

Problems may be hidden underground.


Root Problems

Check for fruiting bodies at the base of a tree that may indicate serious root rot.

This may be the end result!!


Root Problems

Soil Compaction

Grade Changes

Trenching and Excavating


Root Problems

No root flare (lack of taper)

Wilted/scorched leaves

Drooping branches

Early fall color

Premature leaf drop

Water/sucker sprouts

Flowing out of season

Abnormal die-back

Stunted annual growth


Construction damage results in:

Lack of taper

Splits

Scaffold branches with poor attachment


Poor Tree Architecture

Outline

Risk and Liability



Mitigation

TOPPING CREATES WOUNDS THAT LAST A LIFETIME!


Prevention and Correction (Mitigation)

FLUSH CUTS LAST A LIFETIME TOO!



MOWER DAMAGE



Consider fencing off hazard trees if removal is not a “popular” option.


Prevention and Correction(Mitigation)

Performing an INVENTORY of trees on property you manage can be the best preventive step you can take!!



Inventories can provide you with data about the number of hazard trees you have.

Maintenance Needs FrequencyPercent of Total Tree

Population

Corrective Prune 164 8%Crown Reduction High 20 1%Crown Restoration High 55 3%Crown Restoration Low 2 0%Crown Cleaning High 213 11%Crown Cleaning Low 23 1%Hazard Limb High 66 3%Hazard Limb Low 11 1%Hazard Tree 269 14%Raising/Lifting 260 13%Recommended Removal 112 6%Safety Prune Walk/Street 1 0%Safety Prune Utility 1 0%TOTAL 1197 61%



Hazard Tree Web Page: www.na.fs.fed.us/spfo/hazard/index.htm

Evaluation of Hazard Trees In Urban Areas is available through the International Society of Arboriculture at www.isa-arbor.com


Additional Sources of Information:

Tree Support & Lightning Protection

Cabling?

Heavy limbs may be candidates for cabling.

Cabling Hardware

Two cable types 7-strand, common-grade galvanized

More bendable

Extra-high-strength (EHS)Much stronger, but less flexible

Sizes of 3/16-inch to 3/8-inch diameter

Cabling Hardware

Dead-end hardware (one end exposed) Lag eye

Anchor with a closed eye

Lag hook, or J-hook Sizes of 5/16-inch, 3/8-inch, ½-inch, and

5/8-inchRefer to ANSI A300 for hardware

limitations

Left and right lag hooks.

Cabling Hardware

Dead-end hardware Works good on small limbs with hard

wood. Do not install in limbs greater than 8 to

10 inches in diameter. Do not install in limbs with decay. Must seat the full length of the threads.

Cabling Hardware

Through-hardware (both ends exposed)

Threaded rods with amon-eye nuts

Eye bolts

Cabling Hardware

Dead-end grips Used to attach EHS

cable to hardware.

Thimbles must be used!

Cabling Tools and EquipmentDrill with sharp bitsCome-along

Brings two branches together.Cable grip

Used to pull cable to proper tension.Cable aid

Used to spread open thimbles, to tighten lags, and help wrap dead-end grips onto the cable.

Attaching Cable to Hardware

Eye splice Used for 7-strand, common-grade cable.

Cable clamps Alternative to using an eye splice.

Installation Techniques

The hardware should be installed in direct line with the pull of the cable.

The hardware should be installed in direct line with the pull of the cable.

Hardware installed in trees should be no closer togetherthan a distance equal to the diameter of the limb.

Much of the holding power comes from wood that forms after installation.

Installation Techniques

Anchors should not be installed into decayed areas.

The installation of cables in a tree represents an ongoing responsibility.

Cables must be checked annually.

Nonrigid Support Systems

Bracing

Used to reinforce weak or split crotches, or to strengthen decayed areas.

Bracing is used in combination with cabling, not as a substitute.

Bracing

Two types of steal rods Lag-threaded rods

Can be installed as dead-end hardware.Drill hole 1/16-inch to 1/8-inch smaller than diameter

of rod.Advantage is threaded rod itself provides support.

Machine threaded rodsUsed in soft-wooded trees, or decayed wood.Drill hole 1/16-inch to 1/8-inch larger than diameter

of rod.

Threaded rod with nuts and washers.

Bracing

To support a crotch that is not split: A single rod is installed above the crotch. Place 1 to 2 times the branch diameter

above the crotch. Additional braces may be installed below

the crotch, if necessary.To support a split crotch:

Install rod below crotch and through the split.

Guying

Guying of trees tends to be permanent because tree will not produce the necessary roots or wood to support itself.

Ground anchors should be placed no closer to the trunk than two-thirds the distance from the ground to the lowest attachment in the tree.

Guys should be attached about two-thirds the height of the tree.

Guys can present a hazard to pedestrians.

Lightning Protection

A lightning protection system consists of a series of copper conductors that extend from the top of the tree, down the main braches and trunk, and out beyond the tree underground where they are grounded.


Air terminal Copper or bronze point located near top

of treeMain conductor

Copper cable connected to air terminal and running down main branch and the trunk.

Attached at regular 3 feet intervals with approved attachments.


Main conductor Support systems (cables) should be

connected to lightning protection system.

Conductor cable should extend out from the tree and be buried 8 to 12 inches below ground.

System still functional if tree grows around conductor as long as there is no break in the conductor.


Ground rod Conductor cable attached to copper

ground rod that is 10 feet long and ½-inch diameter.

Ground rod should be driven to a depth of 10 feet.

In dry, sandy, or rocky soils, the cable should be forked to several ground rods.

For soil with less than 2 feet of depth, use a ground plate.

In dry, sandy, or rocky soils, the cable should be forked to multiple ground rods.

Thank You!

Josh BehounekDavey Resource Group

[email protected]

Isa training tree risk assessment & cabling bracing

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