Trees and Construction

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Trees and Construction
Keeping Trees Alive in the Urban Forest
Illinois Chapter ISA Chapter 13

• Jennifer Hitchcock

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Trees and Construction

• Outline
• How are trees damaged during construction
• Benefits of saving trees
• Function and location of tree roots
• The tree protection zone
• Tree assessment
• Construction impacts to trees
• Tree protection techniques

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Introduction

• Wooded lots or lots with mature trees bring
  added value to the new home.
• It is imperative that a professional/certified
  Arborist get involved in the planning/design
  stage, not after the construction starts.
• Construction damage is one of the most common
  causes of tree death and decline in urban areas.
• If trees are damaged most often the tree will
  not show symptoms of decline until 3-5 years
  later.

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Damage During Construction

• Injury to crown trunk
• Cutting of Roots
• Compaction
• Smothering of Roots
• Exposure to Elements

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Damage During Construction

• 1. Injury to crown trunk
• Breaking branches
• Damaging the trunks of the tree

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Damage During Construction

• 2. Cutting of Roots
• Severing of one major root can cause 15-25 loss
  of root system
• CASUES OF INJURY
• Digging/Trenching
• Lowering Grade
• Depending on how many anchoring roots have been
  cut and
• the proximity of the cut to the trunk of the
  tree, there is a possible hazard potential of
  tree becoming unstable and falling over.

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Trees and Construction
Root damage
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Damage During Construction

• 3. Compaction
• Soil compaction reduces the pore space resulting
  in the reduction of oxygen and accumulation of
  carbon dioxide and other gases.
• Root growth may be diminished.
• The ability for the root to absorb water and
  minerals is decreased.
• Water infiltration and movement into the soil is
  reduced.
• Roots ability to grow into the soil is also
  reduced.

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Damage During Construction

• 4. Smothering of Roots
• 90 of the fine roots are in the upper few inches
  of
• soil.
• Piling soil on the root system smothers roots
• Raising the grade smothers the roots in addition
  to altering the drainage pattern!
• Sensitive trees such as oaks cannot withstand the
  added 2-3 of soil.

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Damage During Construction

• 5. Exposure to Elements
• Groupings of trees removing the outer trees in
  turn changes the inner trees ecosystem. They are
  now exposed to wind and direct sunlight.
• This can cause breakage and sunscald.
• NOTE
• Roots that are exposed in a trench must be
  covered or will dry out.

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Benefits of Saving Trees

• Energy savings
• Social
• Environmental
• Economic

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Homebuyers will pay more for homes with trees.
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Benefits of Saving Trees
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Increased Market Value
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Decreased Costs
Golf Course County Club Development
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Plan for Tree Protection
A development team should include

• Developer
• Builders
• Certified arborist/urban forester
• Natural resource expert
• Civil engineers
• Utility engineers

• Architect
• Landscape architect
• Contractors
• General
• Grading
• Landscape
• Irrigation
• City/county planner

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Tree Protection Plan Example
Elementary School Development
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Tree Roots Activity
Where are tree roots?
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Tree Roots Fact or Fiction?

• Do most trees have taproots?
• Can roots be as deep as the tree is tall?

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• Some trees have deep roots close to the trunk,
  but most tree roots are concentrated in the upper
  foot of soil.

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Tree Roots Fact or Fiction?

• Do a tree's roots extend only as far as the
  branches?

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• Roots can extend up to three times the dripline
  of the tree.

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Tree Roots Fact or Fiction?

• Do tree roots need oxygen to survive?

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• Tree roots grow best where there is plenty of
  oxygen, water, and nutrients.

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Tree Roots Fact or Fiction?

• Does a tree's entire root system absorb water and
  nutrients?

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• Small diameter roots absorb the most water and
  nutrients.

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Planning Preservation

• The arborist should get involved early in the
  planning stage
• Development should occur with doing the least
  amount of damage to the preserved trees.
• They can decide what trees should be saved and/or
  removed.
• 2. They can provide recommendations on location
  of structures and utilities
• 3. They can provide recommendations on auguring
  vs. trenching.
• 4. They can provide information on the
  pre-construction, during construction and post
  construction care the trees will need.

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Communication

• Arborists must learn to work with engineers,
  developers, planners, builders and home owners.
• Understand the standards and specifications
  required of development as it applies to trees on
  the site.
• The Arborists needs to be able to explain and
  show why and how construction can damage trees!
• Be able to document problems and concerns that
  arise and address them to the appropriate people.

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Tree Protection Specifications

• The tree preservation plan is a road map to
  identify the requirements and specifications of
  tree preservation. The following must be
  included in the specifications to help ensure the
  plans success.
• Tree fence
• Root pruning
• Crown pruning
• Tunneling
• Details on how structures will be built Brick
  vs. concrete
• Bridging

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The Tree Protection ZoneDripline Method
Dripline distance protection zone radius

• Dripline distance 1.5 protection zone radius

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The Tree Protection ZoneDripline Method
Dripline distance protection zone radius

• Dripline distance 1.5 protection zone radius

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The Tree Protection ZoneDripline Method
Dripline distance protection zone radius

• Dripline distance 1.5 protection zone radius

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The Tree Protection ZoneTrunk Diameter Method

• Trunk diameter measured in inchesat 54" above
  soil line 1 ½ ft per inch protection zone
  radius

54"
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Which Trees Should Be Saved?

• Can big trees be saved?

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• Big trees can be saved only with appropriate
  practices.

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Tree Assessment

• Species
• Size
• Location
• Health

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Indicators of Health

• Structure
• Crown
• Age/maturity
• Past damage or improper pruning
• Insects or diseases

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Which Oak Would You Save?
A
B
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Structural ProblemsCodominant Stems
A
B
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Other Structural Problems
Included bark
Trunk openings/decay
Leaning trees
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Crown Problems
Crown ratio
End weight
Dieback
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Age and Maturity
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Past Damage or Improper Pruning
Old wound
Topped
Broken branch
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Insects or Diseases
Wood-rotting fungi
Canker
Wood-boring insects
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Tree Assessment

• Species
• Size
• Location
• Health
• Individual trees

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Individual Trees
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Were These Trees Worth Saving?
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Were These Trees Worth Saving?
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To Minimize DamageWhen Saving Individual Trees

• Pre and post construction treatments

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Tree Assessment

• Species
• Size
• Location
• Health
• Individual trees
• Groups of trees

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Groups of Trees
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To Minimize DamageWhen Saving Groups of Trees

• Keep natural areas undisturbed
• Leave the understory beneath the canopy

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Avoiding Tree Damage During Construction

• Barriers Tree fence the single most important
  action before construction begins.
• Place to drip line of tree or 1 from trunk for
  each tree diameter.
• Nothing happens within fenced area.
• Limiting Access
• Allow 1 access point for all construction
  equipment
• Define limits of storage

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Avoiding Tree Damage During Construction

• Reducing Compaction
• If access is within the drip line, installing a
  6-12 layer of mulch over the critical zone will
  disperse the weight of trucks. In addition to
  this, plywood can be placed on top of the chips.

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Avoiding Tree Damage During Construction

• Changes in Grade
• How much root system will be disturbed?
• Type of species
• Degree the grade will be changed
• Soil conditions
• Surface to be used
• A. Lowering Grade can be accomplished by
• Terracing in steps
• Tree islands
• Must severe roots cleanly and keep them moist

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Avoiding Tree Damage During Construction

• Raising Grade
• Aeration systems and Tree wells
• If to be affective must be installed correctly
  using the appropriate materials and taking into
  consideration the species of tree affected.

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Construction Impacts

• Excavation
• Dumping
• Spilling
• Storage
• Water changes
• Above ground injury

• Clearing
• Compaction
• Grading
• Soil fills
• Pavement installation
• Utilities installation

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Construction Impacts Fact or Fiction?

• Is construction damage to trees easily seen?

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• Damage to trees is more often hidden than seen.

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Construction Impacts Clearing
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To Minimize Damage by Clearing

• Have tree protection in place before clearing
  begins
• Hand clear trees with chain saw
• Leave understory vegetation under trees
• Use specialized equipment

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Construction Impacts Compaction

• Will parking equipment under a tree affect its
  survival?

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Most compaction occurs duringthe first pass of
equipment.
Elephant (50 psi) 2-ton Truck (20 psi) based
on 48 sq in per tire
Average person (10 psi) Bulldozer (10 psi)
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Construction Impacts Compaction
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To Minimize Damage by Compaction

• 12 of mulch in equipment path
• Steel plates over mulch
• Traffic routes

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Construction Impacts Grading

• Does lowering the grade on a site harm tree roots?

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• Removing as little as 2 inches of soil removes
  many important roots.

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Construction Impacts Lowering the Grade
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Construction Impacts Grading

• Will adding 2 inches of soil over the roots harm
  a tree?

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• Adding even small amounts of soil can suffocate
  roots by cutting off oxygen and water.

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Construction Impacts Raising the Grade
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Construction Impacts Grading

• Will building a "tree well" help save a tree from
  the effects of raising the grade?

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• A tree well is no guarantee of tree survival.

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To Minimize Damage by Grading

• Appropriate site design
• Maintain grade as far as possible
• Root prune at edge of excavation
• Channel water away from trees
• Add coarsely textured fill

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Construction Impacts Installation of Utilities
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To Minimize DamageFrom Installation of Utilities

• Consolidation of utilities
• Alter the route
• Tunneling/boring
• Trench only one side of a tree
• Trench work location
• Keep root ends moist

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Construction Impacts Pavement Installation
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To Minimize DamageFrom Pavement Installation

• Adjust finished grades/utilize natural grades
• Select paving that requires the least excavation
• Minimize cuts
• Use extra reinforcement in concrete
• Pervious pavers

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Construction Impacts Excavation
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To Minimize DamageFrom Excavation

• Use a stem wall foundation
• Reinforce the slab
• Thicken the edge of the slab
• Avoid continuous footings next to trees
• Use pier foundations with grade beams above grade
• Excavate by hand

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Other Construction Impacts

• Dumping
• Spilling
• Storage
• Water changes

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To Minimize Damage FromOther Construction Impacts

• Set specific areas for storage and disposal
• Use plastic to prevent spills
• Clean up spills immediately
• Use pesticides according to the label
• Channel water away from trees
• Use grass swales

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Construction Impacts Above Ground Injuries
Wounds
Improper pruning
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To Minimize Damage From Above Ground Injuries

• Prune before construction
• Fence trees
• Prune broken or torn limbs to form clean cuts
• Cut away dead or injured bark

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Construction Impacts Fact or Fiction?

• If a tree survives construction, will it live?

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• Trees may die suddenly after construction ends or

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• trees may show a slow decline over a period of
  years.

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Punchlist for Tree Survival

• Hire a certified arborist early in the process.

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Punchlist for Tree Survival
Inventory trees and select which to save.
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Punchlist for Tree Survival
Protect the trees you plan to save.
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Punchlist for Tree Survival
Do not allow construction activities in the root
protection zone.
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Punchlist for Tree Survival
Communicate the tree protection plan.
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Punchlist for Tree Survival
Plan for accountability.
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Punchlist for Tree Survival
Fines and Penalties for violations This can
include penalties on a per day basis. When stop
work orders will be issued. The Arborist should
visit the site daily. A plan should be posted at
the site for all to see.
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Treatment of Damaged Trees

• Use all the tools at your disposal
• Pruning of broken branches
• Cabling and Bracing
• Repairing Damaged Bark/Trunk
• (bark tracing)
• Irrigation and Drainage decide what measures
  need to be taken to elevate the problem
• Mulching

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Treatment of Damaged Trees

• Aeration of the root zone due to compaction and
• increase in grade.
• Drilling holes/vertical mulching
• 2-4 diameter, 1-3 on center throughout the
  root zone of the tree. Depth 12 filled with
  organic material.
• Radial Trenching
• Trenches are dug in radial pattern throughout
  root zone
• (spokes of a wheel). Begin 4-8 from trunk of
  tree.

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Treatment of Damaged Trees

• Fertilization Not the first year
• Monitoring for Decline and Hazards