protecting the root zone during construction · tree root damage during construction •feeder...

Protecting the Root Zone During Construction

Amy Seiler

Western Community Forestry Specialist

Nebraska Forest Service

Benefits of Trees

• Economic Benefits• Reduce cooling costs

• Increase property values

• Attract business and residents to an area

• Environmental Benefits• Oxygen

• Improve air quality

• Sequester carbon

• Conserve energy

• Reduce stormwater runoff

• Assist with erosion control

• Food and protection for wildlife

• Social Benefits• Where trees are

present:• draw people to an

area

• Lower stress levels

• Reduce hospital recovery times

• Behavioral improvements in children

• Reduce certain types of crime

Information from International Society of Arboriculture

If Trees Benefit Us

Does This Benefit Trees?????

Construction Can Be Deadly to Trees

Review of Roots• Where do roots typically grow?

• Top 6-24” of soil• Cover an area 2 to 4 X diameter of crown

• What are the function of roots?• Water and mineral conduction• Food and water storage• Anchorage

• What are the two kinds of roots and how do they grow?• Large, woody roots• Feeder roots

• Why do roots grow where the do?• Grow where water, oxygen and minerals

are found• Soil aeration and soil temperatures

Tree Root Damage During Construction

• Feeder roots crushed from heavy equipment• Change in grade

• Tree roots buried/smothered

• Tree roots exposed

• Tearing or cutting roots during excavation or trenching

• Soil Compaction

• Other ways trees are damaged during construction• Physical injury to roots, trunk and canopy from equipment or

construction material

• Removing supporting/neighboring trees©2017, Colorado State University Extension, Fort Collins, Colorado 80523 USA

•Two Options• Develop a tree preservation plan

• Builders

• Developers

• Tree Board

• City Arborist

• City Planner

• Campus landscape staff

• Create a tree protection ordinance

Protecting Trees During Construction

• Plan must be in place before project starts• Arborist must be involved and be able to work with:

• Builders• Engineers• Developers• Planners• Landscape Architects

•Determine which trees should be preserved and removed• Condition• Species• Size• Location

Tree Preservation Plans

•Only healthy structurally sound trees should be preserved•Strive to maintain diversity of species and ages•Consider if trees will be tolerant of construction

activity• Large mature trees may not be as tolerant of

construction activity• Smaller more vigorous trees may be more tolerant


•Avoid designing projects around trees that are not structurally sound, in poor condition or unable to survive construction impacts


Photo credit: Eric Berg

• Arborists should work with an architect or engineer to:• Create maps of trees to preserve

• Plans should include:• Boundaries for tree protection zones• Details of mitigation and preservation measures

• Grade changes• Water capture locations

• Write specifications • Should state what can and can’t be done to and around

trees• Should communicate to contractors the purpose of barriers

and specific work zones• Fines and penalties may be built into specifications


• Improve tree vitality

• Develop tree protection zones• Set up barriers around trees with fencing and signage

• Limit access

• Reduce compaction

• Minimizing grade changes

Mitigation and Preservation Measures

• Mulch with 3-4” of mulch around drip line

• Develop a watering schedule for during construction

• Treat for any pests or nutrient deficiencies

• Consider application of tree growth regulators

Improve Tree Vitality

Limit access• Ideally one access route on and off property

• Contractors should be instructed where to drive and park vehicles

• Define Storage areas for• equipment

• soil

• construction material

• cement washout pits

Develop Tree Protection Zones

• Set up barriers around trees with fencing and signage

Photo credit: Altitude Arborist, LLC

Photo credit: gibneyce.com

Critical root zone radius distances calculated by tree diameter at breast height

Tree diameter

Critical root zone

radius

Total protection zone diameter, including trunk

2 inches 2 feet 4+ feet

6 inches 6 feet 13.5 feet

20 inches 20 feet 42 feet

46 inches 46 feet 96 feet

• Each tree has a critical root zone (CRZ) that varies by species and site conditions. • CRZ is an area equal to 1’ radius from the base of the tree’s trunk for each inch of the

tree’s diameter at DBH (4.5’ above grade)

Reduce compaction

• Mulch• Spread 6-12” of course wood chip

mulch on construction site

• Additional protection around roots• Add large plywood or steel sheets

over mulch to disperse load of heavy equipment

Photo credit: gibneyce.com

Minimize Effects of Grade Changes

• When grades must be lowered:• Tree islands with retaining walls

• Feathered slopes

• When grades must be raised:• Do not use gravel as fill

• Use fill soil similar in texture to native soil

• Have knowledge of trees that can tolerate additional soil over roots• Trees that are native to flood

• http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

Preventing Damage to Tree Roots During Trenching or Sidewalk Construction

• Alter the Route

• Keep trench outside the dripline

• When roots are exposed, keep the moist

• If you must cut roots, make sharp cuts

• Tunneling or boring

When Roots are Exposed, Keep them Moist

• Monitor trees during construction

• Enforce the tree protection zone (TPZ)

• Assist with changes in the field

• Monitor injury to trees and provide corrective action

• Communicate with project manager

Roll of Arborist During Construction

• http://wanakahcccom.blogspot.com/2011/10/tree-root-pruning.htmlDiscussion

http://wanakahcccom.blogspot.com/2011/10/tree-root-pruning.html

• Acknowledgements: • International Society of Arboriculture

Arborist Study Guide• ISA Best Management Practices

Managing Trees During Construction

• Colorado State Forest Service

• University of Florida Fact Sheets and Ed Gilman

• Arbor Day Foundation Tree City USA Bulletin #35 “How to Protect Trees During Construction”

Questions?????

Amy Seiler,Community Forestry SpecialistNebraska Forest [email protected]

mailto:[email protected]

Resources

• https://www.smgov.net/uploadedFiles/Portals/UrbanForest/Maintenance/TreeProtectionGuidelines.pdf

• https://content.ces.ncsu.edu/construction-and-tree-protection

• http://gibneyce.com/14-read-about-trees-on-building-sites.html

• http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

• ISA Best Management Practices Managing Trees During Construction
https://www.smgov.net/uploadedFiles/Portals/UrbanForest/Maintenance/TreeProtectionGuidelines.pdfhttps://content.ces.ncsu.edu/construction-and-tree-protectionhttp://gibneyce.com/14-read-about-trees-on-building-sites.htmlhttp://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

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