Construction around existing trees can cause serious long term damage.
We often forget that half the tree is below ground and it is the tree below ground that suffers most during construction.

The following document is the draft of a proposed standard for protection of trees. This document is open for comment and can be made to treedoc@ozdocs.net.au or bruno@treexpert.com.au

Draft 97_1.2

INTRODUCTION
1 SCOPE
2 AIM
3 APPLICATION
4 DEFINITIONS
5 THE TREE AS A SYSTEM
6 PRE PLANNING & PLANNING
7 PRE CONSTRUCTION
8 TREE PROTECTION ZONES
9 MAINTENANCE ACTIVITIES
10 FENCING
11 OTHER PROTECTION TECHNIQUES
12 SIGNS
13 ROOT SEVERANCE
14 MAINTENANCE REPORTS
15 NON CONFORMANCE REPORTS
16 LANDSCAPE CONSIDERATIONS

INTRODUCTION
Construction activities usually have an adverse or detrimental affects on trees. Well meaning individuals usually cause serious damage to trees during construction. This can sometimes result in death, severe short and long term decline or physical failure of the tree.

Frequently the damage is not apparent until after construction has been completed and the typical defects liability period of 12 months is over. Often the damage only becomes apparent several years
later.

The desire to retain trees but the failure to obtain advise from an Arborist and to make adequate allowance for their retention is also another common cause for problems with Protection of Trees on Construction Sites.

In almost all cases the problem with trees on construction sites arises from:

· A lack of understanding of trees and how they function.
· A lack of knowledge regarding the value and benefit of trees.
· A failure to obtain proper advice from an Arborist during the planning stage.
· The lack of a systematic approach to prevent damage by the use of active protection techniques and maintenance (eg. fencing and irrigation).
· The failure to seek sufficient expertise and intervention over the long term.

The involvement of an Arborist is an essential component to successfully managing trees.

The purpose of this document is to provide consistent and uniform standards and minimum guidelines for the retention, protection and care of trees on construction sites. Whilst it will provide a valuable reference for builders and developers it is not a "self help" book and will require active and ongoing involvement of a qualified Arborist

A developer, architects, engineers, building inspectors, town planners/builder, landscape architect or planner will however be able to clearly define and quantify the level of professional advice and tree protection that will be required.


1 SCOPE

This document describes the role of an arborist in the Protection of Trees on Construction Sites and the methods and materials required as a minimum to protect trees on construction sites. It also gives valuable guidelines to the activities that should and should not be carried out adjacent to tree(s).

2 AIM
To provide documentation and an action plan that can be readily adapted for the process of protecting trees on construction sites.
3 APPLICATION

These guidelines apply to the protection of all woody plants and trees on construction sites. They cover issues to be addressed during the design process right through to post construction maintenance. It is intended for use by those who are involved in the design, planning approval stage, construction industries and by the arborists responsible for the protection of the trees.
4 DEFINITIONS

The terms listed below are incomplete. They are to be supplemented wherever required by Australian Standard AS 4373-1996 Pruning of Amenity Trees, and NATSPEC Guide to "Purchasing Landscape Trees"
4.1 Arborist: one who is formally qualified or certified in Arboriculture with at least 3 years documented experience in Arboriculture.
4.2 Arboriculture: The care of trees and wood trees in the urban environment.
4.3 Barricade: A temporary structure usually made from star pickets and barricading tapes or rolls.
4.4 EC meter: A device measuring the level of dissolved salts used to indicate levels of fertilizers etc
4.5 Drip line: The area under the canopy of a tree.
4.6 D.B.H: Diameter of the tree at Breast height (i.e. 1.2 meters.)
4.7 Fence (rigid): A solid structure that prevents free access by people and machinery.
4.8 Field Capacity: The maximum water storage capacity of soil after free gravity drainage has occurred.
4.9 Mulch: a layer of organic or inorganic matter placed on the surface of the soil intended to reduce soil moisture loss and weed growth and on occasions limit soil compaction.
4.10 Mycorrhizae: A beneficial root-fungi association where the fungi aids in the absorption of water and minerals by the roots in exchange for carbohydrates.
4.11 Nitrogen drawdown: the rapid uptake of nitrogen by micro-organisms during the sudden rapid initial decay of undecomposed organic material in an aerobic environment (usually at or near the surface).
4.12 Non Woody Root: A tee root that contains little to no lignin and no corky outer bark that is responsible for the uptake of water and dissolved elements. These are usually less than 1 mm in diameter and never any thicker than several millimeters.
4.13 Palm: A woody perennial monocotyledon with one or more stems from the order arecacae.
4.14 Palm Roots: Unlike tree roots, these branch less, do not grow in thickness with age and have no bark or meristematic zone surrounding the root.
4.15 Penetrometer: A device used to measure the destiny / compaction of soil.
4.16 Root zone. The area where tree roots can be found.
4.17 Tensiometer: A device that gives a quantitative reading of the amount of available water in the soil.
4.18 Tree: A woody , perennial, dicotyledon, with one or several stems which potentially grows to a height of more than 3 meters.
4.19 Trunk flare: the zone at the base of a tree trunk where it rapidly becomes wider and enters the ground as well as the area up to approximately 2m from the trunk where large structural roots are close to the ground surface.
4.20 Turgor: The rigidity of plant cells, organs and parts resulting from hydrostatic pressure exerted on the cell wall.
4.21 Wilt Point: The level of soil moisture at which no free moisture is available for uptake by the tree. This results in wilting and or other stresses and strain.
4.22 Woody Root: A root that has high amounts of lignin and a corky outer bark. These roots are important for energy storage, conduction of water and dissolved elements and structural support of the tree.
5 THE TREE AS A SYSTEM

Trees are, in themselves, complex organisms. Equally, they have developed complex associations with many other organisms.

Put simply, trees are woody plants with two main absorptive parts (leaves and non woody roots) at either end of a conductive system (branches stems and woody roots). Surprisingly there are usually far more absorptive tips below ground than there is above ground i.e. there are more roots than leaves. Those absorptive parts above ground are called leaves, needles or fronds and the portion below ground are the roots.

Damage one part of the tree and you damage the system as a whole.

The leaves absorb carbon dioxide and sunlight and through a process called photosynthesis produce carbohydrates, the energy required for growth and respiration. Non-woody roots, on the other hand, absorb water and all the dissolved elements also required by the tree for healthy growth.

The conductive parts are woody. They include branches, trunks and woody roots. Wood is a highly ordered arrangement of cells that are living, dying or dead. These cells have walls of cellulose, hemicelluloses, and lignin.

Wood is the part of the tree used for storage and in particular the storage of energy reserves. Woody roots store more energy than branches. Woody roots are also responsible for providing anchoring and support of the tree.

All the living cells in the tree utilize (or metabolize) carbohydrates. To do this they require not just carbohydrates but also OXYGEN in a process known as 'respiration'. All living parts of the tree need to respire and will SUFFOCATE if the levels of oxygen falls below a critical level. It can sometimes take months or even years for this damage to manifest itself.

The association that trees have is complex but vitally important. The vast majority of these occur under ground in the area around the roots. This area, called the Rhizosphere, is both complex and vital to the survival of the tree. It is in this zone that we find mycorrhizae. Mycorrhizae is the interdependent relationship between a fungus and a non woody roots that acts as a single organ of the tree. There are also important bacteria, decay fungi and microflora.

So much important activity of trees occurs underground from roots to the Rhizoshpere. Construction frequently involves extensive changes at and below ground. Because of this, construction can have both short and long term adverse affects on a tree.

6 PRE PLANNING & PLANNING

6.1 Prior to site planning, existing trees on the site should be inspected by a consulting arborist to determine their health, vigour and structural integrity.
6.2 A site survey accurately indicating the location of all trees.
6.3 A tree list and survey shall be supplied indicating genus and species, where possible along with DBH, height and spread of canopy. Also any important observations such as health and structural problems or special considerations as well as any recommended works i.e. pruning, removal, soil amelioration should be noted.
6.4 Any information supplied by an Arborist must satisfy local council requirements.
6.5 Where appropriate an estimation of age, life expectancy, and tolerance to construction activities may also be provided.
6.6 A tree valuation may be required for the purposes of determining bonds or the value of the amenity that may need to be replaced in the event of tree removal.
6.7 Trees that can be transplanted should be noted so that consideration can be given to their use in the future landscape.
7 PRE CONSTRUCTION

Prior to the commencement of construction a consulting arborist shall issue a report outlining the following:

7.1 The trees that have been protected, the maintenance activities (if any) for each tree, the size of the protection zone for each tree and type of protective fencing installed.
7.2 A statement that the physical protection (items 7 and 8) of the trees has been performed to the above standards or if not, any nonconformance and the reason for the nonconformance, e.g. the fencing around tree is incomplete due to the presence of a boundary fence.

8 TREE PROTECTION ZONES

The protection zone can be divided into 5 basic classes.

8.1 The Critical Root Zone (CRZ): This is the most critical root area. It can be defined as the area 10 times the diameter of the trunk. It is the base area that should be designed to remain unaltered by cut, fill, trenching or liquid chemical overland flow throughout the construction phase.
8.2 The Primary Root Zone (PRZ): This is the area to the dripline or outer edges of the canopy or a circle the radius of the height of the tree whichever is greater. Activity in this area should be limited. The area can be altered with the guidance of an arborist in conjunction with these standards.
8.3 The Auxiliary Root Zone (ARZ): The Auxiliary Root Zone is the area one and a half times the canopy or a radius one and a half times the height of the tree whichever is greater. Activities in this area have less affect on the tree. There are still some activities that are not permitted in this area.
8.4 The Root Graft Zone (RGZ): This is an area 5 times the height of the tree or 5 times the canopy of the tree which ever is greater. The zone only exists if another tree of the same Genus falls within this zone. The use of systematic herbicides in this zone on trees which have a specimen of the same genus which is to be retained in this zone is prohibited.
8.5 Palm Protection Area (PPA): This is an area not less than 4 square meters and having a minimum soil volume of 4 cubic meters.

9 MAINTENANCE ACTIVITIES

9.1 Maintenance Overview

9.1.1 Maintenance activities: These include but are not limited to irrigation, soil amelioration, mulching, weed control, soil aeration and crown cleaning in accordance with AS 4373 - 1996 - Pruning of Amenity Trees, removal of trees by sectional felling and stump grinding.
9.1.2 Timing: qualified Arborists may perform Maintenance activities at any time during the construction process. Maintenance should be performed at regular intervals.
9.1.3 Controlled activities: These activities should occur only after approval and specifications have been provided by an Arborist and include, trenching, root severance, soil truncation, soil build up, vehicular and pedestrian traffic access, and pruning other than crown cleaning.

9.2 Irrigation

9.2.1 Soil moisture during construction shall be maintained at not less than 50% of field capacity.
9.2.2 Irrigation may be applied by hand, automatic or manual irrigation system, or by fine spray from a water tanker located outside the tree protection zone. Water is to be applied at a volume and frequency required to maintain turgor and leaf retention and encourage healthy root development.
9.2.3 On each and every visit the consulting arborist shall check the soil moisture and manually check the irrigation system, if installed.
9.2.4 Soil moisture levels should be checked by physical touch (the pinch test - see *) or with a tensiometer.
9.3 Soil amelioration

9.3.1 Bio-stimulants such as rooting hormones, humic acids, soil microflora and mycorrhizae should be applied by an arborist in accordance with the manufacturers instructions.
9.3.2 The use of chemical fertilizers should only be performed after laboratory testing, of either the soil or the soil and the foliage, and in accordance with those test results.
9.3.3 The use of nitrogenous fertilizers must not be used where Phytophora is suspected or has been diagnosed.
9.3.4 The use of fertilizers with phosphorous should be avoided around natives, particularly Proteacae. The use of phosphate liberating bacteria is preferred.
9.4 Mulching

9.4.1 Mulch, when applied, will be free of weeds and shall be applied at no greater thickness than 100mm. Mulch should be applied to the surface and not mixed with the soil. Mulch with an appropriate carbon to nitrogen ratio should be selected as recommended by the arborist.
9.5 Weed Control

9.5.1 Weed control shall be by hand pulling, wiping or spraying with a glyphosate based or other appropriate herbicide.
9.5.2 Weed control shall never be performed by mechanical cultivation or by scraping or back burning.

9.6 Aeration

9.6.1 An arborist should perform soil decompaction only after testing with a penetrometer or similar device indicates it is necessary. Decompaction may include the use of a Grow Gun, vertical mulching or radial trenching.
9.6.2 The arborist performing decompaction activities should carefully evaluate the soil structure and the pattern of root activity prior to choosing and implementing a decompaction program.

9.7 Crown cleaning

9.7.1 Crown cleaning (AS4373-1996, Pruning of Amenity Trees) shall be performed in accordance with the standard by an arborist and in compliance with the appropriate occupational health and safety regulations.
9.7.2 Any concerns about health or safety that are observed by the arborist on the site should be reported in writing within 7 days to the superintendent/principal/client and/or head contractor.
9.7.3 The use of spurs on live trees and internodal cutting should be prohibited.

9.8 Tree removal and stump grinding

9.8.1 Sectional felling and stump grinding shall be used to remove trees. Care shall be taken not to damage any adjacent trees that are to remain.
9.8.2 The extent and depth of grinding of stumps shall be determined and agreed upon by the arborist and the contractor prior to grinding. Consideration shall be given to the location of trees that are to remain and the pattern and location of their roots. The ground out stump is to be filled with planting soil to finish flush with the adjacent ground levels.

10 FENCING

10.1 The tree protection zone (Primary root zone at minimum) should be determined by an arborist and fenced prior to the commencement of ANY work, including demolition and land clearing by earth moving machinery but may be erected after maintenance activities (see 6 above).
10.2 The fencing surrounding the CRZ and PRZ must be a rigid fence not less than 1.8m high.
10.3 If the protection zone extends into the ARZ or further, the portion of fence protecting this zone may be barricading.
11 OTHER PROTECTION TECHNIQUES

Site-specific design solutions should be developed in consultation with an arborist. Due to site variations prescriptive solutions cannot be given.

11.1 Temporary roadways should be designed to mimimise soil compaction and to avoid changes of the grade. These designs may use geo-textile fabrics, structurally gaped aggregate, mulch, and metal plates.
11.2 Service installation should avoid trenching through the primary and critical root zone. The use of horizontal boring is preferable.
11.3 Siltation and water inundation should be avoided by the use of silt traps and appropriate drainage.
11.4 Where construction is required within the CRZ techniques such as pier and suspended slabs, canter levering, decking and other systems should be considered.
12 SIGNS

12.1 A minimum of two signs should be attached to all tree protection areas at no greater than 20 meter intervals. The signs should be a minimum of 600mm x 600mm, bearing the following phrase in red letters on white background at least 50mm in height:

TREE PROTECTION ZONE - KEEP OUT.

12.2 On the same sign above or on a separate sign attached adjacent, in red lettering on white background not less than 25mm in height is to be the following

PROHIBITED ACTIVITIES:
followed by the list below in letters not less than 15mm
Prohibited Activities:
a) entry of machinery or people.
b) storage of building materials.
c) parking of any kind.
d) erection or placement of site facilities.
e) removal or stockpiling of soil or site debris.
f) disposal of liquid waste including paint and concrete wash.
g) excavation or trenching of any kind (including irrigation or electrical connections).
h) attaching any signs or any other objects to the tree.
i) placement of waste disposal or skip bins.
j) pruning and removal of branches, except by a qualified Arborist.

12.3 The name of the supervising Arborist or Arboricultural company and a contact phone number should be displayed on the sign in letters not less than 25mm in height.

13 ROOT SEVERANCE

12.1 All roots greater than 25mm in diameter that are required to be removed shall be cleanly cut and kept moist at all times and shall not be left exposed to the air. (see appendix D - Root curtains)

14 MAINTENANCE REPORTS

14.0.1 Inspection period. Where the trees on a site and their primary root zone are retained, a monthly inspection and report by an arborist is required.
14.0.1 Where construction activity is to occur within the primary root zone, weekly inspections and monthly reports shall be provided until the end of construction.
14.0.2 Where construction activity is to occur within the critical root zone, a consulting arborist shall be on site during the performance of such work and shall document and report on that work along with performing weekly inspections and monthly reports until the completion of construction activities on site.

14 Site Log

14.2.1 A site log shall be maintained and include the date of each inspection, the person who performed the inspection, the items inspected or tested, the maintenance activities performed, any repairs undertaken or required to be undertaken, and any substantial breaches or nonconformances.
14.2.2 The entries in the log book shall be signed by the arborist performing the inspection.
14.2.3 The log shall be maintained on site or alternative copies of the log entries for the month shall be submitted each month with the monthly report.

15 NON CONFORMANCE REPORTS

15.0.1 The removal of all or part of any protective fence.
15.0.2 The performing of any activity noted as prohibited on protection zone signage (SEE 8.21)
15.0.3 The failure to maintain adequate soil moisture (SEE 6.21 and 6.24) or the faulty of the irrigation system.
15.0.4 Mechanical damage to the trunk, stems, branches or retained roots.
15.0.5 The sudden and abnormal or premature shedding or decline of the tree.
15.0.6 Substantial breaches and non conformances
15.0.7 Any breach or nonconformance of the tree protection zone, by any party, shall be notified in writing within 2 working days of it being first observed.
15.0.8 Notification may be made to the following as directed in the contract. The Arborist , builder, contractor / subcontractor or person responsible for the breach. Any council officer required as a condition of the DA or BA, any other parties required by the contract.

16 LANDSCAPE CONSIDERATIONS

The installation of landscaping during the finishing stages of construction requires careful planning and implementation.

The landscape construction often requires that all tree protection fencing be removed. This can leave all trees vulnerable to landscape construction damage. Tree protection fencing should only be removed after consultation with the supervising arborist.

An arborist must approve all landscape installations that are likely to impact on the tree. These may include, installation of irrigation, paths, access roads, lights and fittings, signs, turf, ponds, cuts and fills.

PROTECTION OF TREES
ON CONSTRUCTION SITES

(POTOCS)

Mark Hartley
The Tree Doctor
Bruno Wright
CANOPY, Tree Experts

Copyright Release

POTOCS is covered by copyright. Its use is restricted to the trees for which a report was sort and to any and all other trees on the same site only.

The use of any or all sections of this document in any documentation relating to this site is permissible so long as the copyright is noted at the completion of any and all portions.

Any other use of this document or the use of this document or any part thereof for any other purpose or in documentation for any other site is strictly prohibited.

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