Tree Protection Zones, Australia 4970-2009(+a1)

Page 1 LICENCE for Licensee: Date: Click on the red box above to activate the Licence Agreement scroll bar Learn about LexConnect, All Jurisdictions, Standards referenced in Australian legislation Know when a Standard has changed Visit our store to find more Publications Page 2 AS 4970—2009 (Incorporating Amendment No. 1) Australian Standard® Protection of trees on development sites AS 4970—2009 Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 3 This Australian Standard® was prepared by Committee EV-018 (formerly BD-068), Arboriculture. It was approved on behalf of the Council of Standards Australia on 31 July 2009. This Standard was published on 26 August 2009. The following are represented on Committee EV-018 (formerly BD-068):  Australian Council of National Trusts  Australian Institute of Building Surveyors  Australian Institute of Horticulture  Australian Institute of Landscape Architects  Australian Local Government Association  Australian Pipeline Industry Association  Australian Property Institute  Energy Networks Association  Institute of Australian Consulting Arboriculturists  International Society of Arboriculture (Australia Chapter)  Local Government Tree Resources Association  National Arborists Association of Australia  Nursery and Garden Industry Australia  Parks and Leisure Australia  TAFE NSW  The University of Melbourne  Water Services Association of Australia Additional Interests:  National Trusts of Australia NSW  Wollongong City Council This Standard was issued in draft form for comment as DR AS 4970. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period. Keeping Standards up-to-date Australian Standards® are living documents that reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting www.standards.org.au Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at mail@standards.org.au , or write to Standards Australia, GPO Box 476, Sydney, NSW 2001. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 4 AS 4970—2009 (Incorporating Amendment No. 1) Australian Standard® Protection of trees on development sites First published as AS 4970—2009. Reissued incorporating Amendment No. 1 (March 2010). COPYRIGHT © Standards Australia All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 9229 4 Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 5 AS 4970—2009 2 PREFACE This Standard was prepared by the Standards Australia Committee EV-018, Arboriculture. This Standard incorporates Amendment No. 1 (March 2010). The changes required by the Amendment are indicated in the text by a marginal bar and amendment number against the clause, note, table, figure or part thereof affected. This Standard provides guidance for arborists, architects, builders, engineers, land managers, landscape architects and contractors, planners, building surveyors, those concerned with the care and protection of trees, and all others interested in integration between trees and construction. This document describes the best practices for the planning and protection of trees on development sites. The procedures described are based on plant biology and current best practices as covered in recently published literature. The assistance obtained from the 1991 and 2005 editions of BS 5837, Trees in relation to construction—Recommendation , along with Matheny and Clark (1998)* and Mattheck and Breloer (1994)* is acknowledged. The term ‘informative’ has been used in this Standard to define the application of the appendix to which it applies. An ‘informative’ appendix is only for information and guidance. * See bibliography in Appendix E for details. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 6 3 AS 4970—2009 CONTENTS Page FOREWORD....................................................................................................................... ....... 4 SECTION 1 SCOPE AND GENERAL 1.1 SCOPE ..................................................................................................................... ... 5 1.2 APPLICATION ........................................................................................................... 5 1.3 REFERENCED DOCUMENTS .................................................................................. 5 1.4 DEFINITIONS ............................................................................................................ 5 SECTION 2 PLANNING AND THE TREE MANAGEMENT PROCESS 2.1 TREE MANAGEMENT PROCESS ............................................................................ 7 2.2 DETERMINING AUTHORITIES ............................................................................... 7 2.3 PLANNING................................................................................................................. 8 SECTION 3 DETERMINING THE PROTECTION ZONES OF THE SELECTED TREES 3.1 TREE PROTECTION ZONE (TPZ).......................................................................... 11 3.2 DETERMINING THE TPZ ....................................................................................... 11 3.3 VARIATIONS TO THE TPZ .................................................................................... 11 SECTION 4 TREE PROTECTION MEASURES 4.1 GENERAL ................................................................................................................ 15 4.2 ACTIVITIES RESTRICTED WITHIN THE TPZ ..................................................... 15 4.3 PROTECTIVE FENCING ......................................................................................... 15 4.4 SIGNS ..................................................................................................................... .. 16 4.5 OTHER TREE PROTECTION MEASURES ............................................................ 16 4.6 MAINTAINING THE TPZ........................................................................................ 19 SECTION 5 MONITORING AND CERTIFICATION 5.1 GENERAL ................................................................................................................ 20 5.2 TREE PROTECTION PLAN..................................................................................... 20 5.3 PRE-CONSTRUCTION ............................................................................................ 20 5.4 CONSTRUCTION STAGE ....................................................................................... 20 5.5 POST-CONSTRUCTION.......................................................................................... 21 APPENDICES A DIAMETER AT BREAST HEIGHT (DBH) ............................................................. 23 B POTENTIAL DAMAGE TO TREES ON DEVELOPMENT SITES......................... 24 C TREE PROTECTION ZONE SIGN EXAMPLE ....................................................... 28 D ENCROACHMENT INTO TREE PROTECTION ZONE......................................... 29 E BIBLIOGRAPHY...................................................................................................... 30 Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 7 AS 4970—2009 4 FOREWORD Landscape design is an important component of most development. Established trees of appropriate species and sound structure are beneficial components of the built environment and a potential asset to any development site. Trees may be retained because of their— (a) aesthetic qualities; (b) heritage values; (c) ecosystem benefits, including— (i) stormwater man agement; (ii) shade and heat reduction qualities; (iii) wildlife habitat and biodiversity; (iv) carbon dioxide absorption; (v) particulate pollution capture; (vi) salt wind protection; and (d) social and psychological values. A living tree is a dynamic organism that needs specific environmental conditions to continue healthy, stable growth. It is rarely possible to repair stressed and injured trees, so substantial injury needs to be avoided during all stages of development and construction. For trees to be retained and their requirements met, procedures must be in place to protect trees at every stage of the development process. This s hould be taken into account at the earliest planning stage of any outdoor event or design of a development project where trees are involved. Trees and their root systems may occupy a substantial part of any development site and because of their potential size, can have a major influence on planning the use of the site. Existing trees of appropriate species and sound structure can significantly enhance new development by providing immediate benefits such as shade and stormwater reduction as well as complementing new development. Most trees will t ake many years and possibly decades to establish but can be injured or killed in a very short time as their vulnerability is commonly not understood. This is especially so in relation to tree root systems which cannot usually be seen. Irreparable injury frequently occurs in the early stages of site occupation and remedial measures routinely fail. Early identification and protection of important trees on development sites is essential from the outset and will minimize the problems of retaining inappropriate trees. Successful long term retention of trees on development sites depends on an acceptance and acknowledgment of the constraints and benefits that existing trees generate. Protecting trees in accordance with this Standard may influence design and construction costs and this should be considered in project budgets and contracts. The gains and benefits of retaining trees will accrue if the measures detailed in this Standard are applied. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 8 5 AS 4970—2009 www.standards.org.au © Standards Australia STANDARDS AUSTRALIA Australian Standard Protection of trees on development sites SECTION 1 SCOPE AND GENERAL 1.1 SCOPE This Standard provides guidance on the principles for protecting trees on land subject to development. It follows, in sequence, the stages of development from planning to implementation. This Standard aims to assist those concerned with trees in relation to development. Where development is to occur, the Standard provides guidance on how to decide which trees are appropriate for retention, and on the means of protecting those trees during construction work. It does not argue for or against development, or for the removal or retention of trees nor does it consider the monetary value of trees. The Standard does not apply to the establishment of new trees. 1.2 APPLICATION This Standard gives guidance to horticulturists, arborists, architects, builders, engineers, land managers, landscape architects, contractors, planners, determining authorities, building surveyors, certifiers, those concerned with the care and protection of trees, and all others involved in the management of trees and development. 1.3 REFERENCED DOCUMENTS The following documents are referred to in this Standard: AS 1319 Safety signs for the occupational environment 4373 Pruning of amenity trees 4454 Composts, soil conditioners and mulches 4687 Temporary fencing and hoardings 1.4 DEFINITIONS For the purpose of this Standard, the following definitions apply: 1.4.1 Determining authority Those bodies responsible for issuing approvals. 1.4.2 Development Includes the following: (a) The use of land (e.g. festival events, use of park areas and other events) that requires approval. (b) The subdivision of land. (c) The erection of a building. (d) The carrying out of a work. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 9 AS 4970—2009 6 © Standards Australia www.standards.org.au (e) The demolition of a building or works. (f) Road works. (g) The installation of utilities and services. (h) Any other act, matter or thing as defined by the relevant legislation. 1.4.3 Diameter at breast height (DBH) The nominal trunk diameter at 1.4 m above ground level determined from the circumference of the trunk divided by pi (π) (see Appendix A). 1.4.4 Project arborist The person responsible for carrying out the tree assessment, report preparation, consultation with designers, specifying tree protection measures, monitoring and certification. The project arborist will be suitably experienced and competent in arboriculture, having acquired through training, qualification (minimum Australian Qualification Framework (AQF) Level 5, Diploma of Horticulture (Arboriculture)) and/or equivalent experience, the knowledge and skills enabling that person to perform the tasks required by this Standard. 1.4.5 Structural root zone (SRZ) The area around the base of a tree required for the tree’s stability in the ground. The woody root growth and soil cohesion in this area are necessary to hold the tree upright. The SRZ is nominally circular with the trunk at its centre and is expressed by its radius in metres. This zone considers a tree’s structural stability only, not the root zone required for a tree’s vigour and long-term viability, which will usually be a much larger area. 1.4.6 Tree Long lived woody perennial plant greater than (or usually greater than) 3 m in height with one or relatively few main stems or trunks (or as defined by the determining authority). 1.4.7 Tree protection zone (TPZ) A specified area above and below ground and at a given distance from the trunk set aside for the protection of a tree’s roots and crown to provide for the viability and stability of a tree to be retained where it is potentially subject to damage by development. 1.4.8 Vigour Ability of a tree to sustain its life processes. The term ‘vigour’ in this document is synonymous with commonly used terms such as ‘health’ and ‘vitality’. 1.4.9 Work Any physical activity in relation to land that is specified by the determining authority. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 10 7 AS 4970—2009 www.standards.org.au © Standards Australia SECTION 2 PLANNING AND THE TREE MANAGEMENT PROCESS 2.1 TREE MANAGEMENT PROCESS The success of the tree management process will depend on the cooperation of all involved in the design and development team. In particular, it is essential for those involved in site works to appreciate the need for maintaining the area of protection around the trees. An example of the tree management process in r elation to the stages of a typical development is set out in Table 1. NOTE: Appendix B outlines potential damage to trees on development sites. 2.2 DETERMINING AUTHORITIES Legal controls and liabilities under common law should be considered at the earliest stages of potential site development. NOTE: Trees may be subject to legislation. Where development is proposed, additional protection may be appropriate and may be enforced by a determining authority. Determining authorities have an important role in encouraging and enforcing the development process. Table 1 indicates the common stages in the development process and typical considerations and actions applicable to trees. When development has been approved, planning conditions may be imposed for the management of trees. TABLE 1 INDICATIVE STAGES IN DEVELOPMENT AND THE TREE MANAGEMENT PROCESS Tree management process Stage in development Matters for consideration Actions and certification Planning (Sections 2 and 3) Site acquisition Legal constraints Detail surveys Council plans and policies Planning instruments and controls Heritage Threatened species Existing trees accurately plotted on survey plan Preliminary tree assessment Hazard/risks Tree retention value Evaluate trees suitable for retention and mark on plan Provide preliminary arboricultural report and indicative TPZs to guide development layout Preliminary development design Condition of trees Proximity to buildings Location of services Roads Level changes Building operations space Long-term management Planning selection of trees for retention Design review by proponent Design modifications to minimize impact to trees (continued ) Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 11 AS 4970—2009 8 © Standards Australia www.standards.org.au Tree management process Stage in development Matters for consideration Actions and certification Development submission Identify trees for retention through comprehensive arboricultural impact assessment of proposed construction. Determine tree protection measures Landscape design Provide arboricultural impact assessment including tree protection plan (drawing) and specification Development approval Development controls Conditions of consent Review consent conditions relating to trees Pre-construction (Sections 4 and 5) State based OHS requirements for tree work Compliance with conditions of consent Approved retention/removal Tree removal/tree retention/transplanting Refer to AS 4373 for the requirements on the pruning of amenity trees Tree pruning Certification of tree removal and p runing Initial site preparation Specifications for tree protection measures Establish/delineate TPZ Install protective measures Certification of tree protection measures Construction (Sections 4 and 5) Site establishment Temporary infrastructure Demolition, bulk earthworks, hydrology Locate temporary infrastructure to minimize impact on retained trees Maintain protective measures Certification of tree protection measures Construction work Liaison with site manager, compliance Deviation from approved plan Maintain or amend protective measures Supervision and monitoring Implement hard and soft landscape works Installation of irrigation services Control of compaction work Installation of pavement and retaining walls Remove selected protective measures as necessary Remedial tree works Supervision and monitoring Practical completion Tree vigour and structure Remove all remaining tree protection measures Certification of tree protection Post construction (Section 5) Defects liability/ maintenance period Tree vigour and structure Maintenance and monitoring Final remedial tree works Final certification of tree condition NOTES: 1 Owing to variations in planning legislation this table is a general indication of the process only. 2 Certification of tree protection and c ondition should be carried out by the project aborist. 2.3 PLANNING 2.3.1 Site survey A detailed topographical survey should be made showing all existing site features. NOTE: This should be made by a registered surveyor. The survey plans should include— (a) location of all individual trees or groups of trees and other vegetation; TABLE 1 (continued ) Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 12 9 AS 4970—2009 www.standards.org.au © Standards Australia (b) location of trees on land adjacent to the development site that may be impacted by the development; (c) crown spread, measured and drawn to scale, defining the actual crown spread; (d) other features, such as streams, creeks, watercourses, buildings and above and below ground services; and (e) spot heights of ground level throughout the development site and specifically including level at the base of individual trees as a basis for evaluating changes in soil level around retained trees. NOTES: 1 Before commencing this survey, advice should be sought from the project arborist to confirm relevant items for inclusion in the survey. 2 Other vegetation may need to be surveyed to meet specific provisions of the determining authority or legislation. 2.3.2 Preliminary tree assessment The preliminary assessment of the trees should take place at the beginning of the project, once any site surveys have been completed. The purpose of this assessment is to provide quantitat ive and qu alitative information on the trees. All trees included in the site survey should be numbered and assessed by the project arborist as the basis for deciding which trees are suitable for retention. For each tree consideration should be given to— (a) correct botanical identification and common name; (b) vigour; (c) structure; (d) dimensions, height, crown spread and DBH; (e) age class; (f) estimated life expectancy; (g) heritage and/or cultural matters (refer Note 3); (h) ecological and habitat matters (refer Note 3); (i) the location relative to existing site features, e.g. its function as a screen or as a landmark feature; (j) other matters relevant to the site, e.g. surface roots; and (k) retention value. NOTES: 1 These criteria should also be recorded for trees surveyed on adjacent properties. 2 Accuracy of the survey data to be verified by the arborist. 3 Input from other specialists may be required. 4 If trees require tagging use a temporary, non-injurious method. 5 A number of commonly used assessment methods are contained is documents listed in Appendix E. 2.3.3 Preliminary arboricultural report Tree protection is most effective when considered at the earliest st age of de velopment planning. The process will require reports at different stages. The most crucial reports are the Preliminary Arboricultural Report and the Arboricultural Impact Assessment. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 13 AS 4970—2009 10 © Standards Australia www.standards.org.au The preliminary report is not intended to be the comprehensive tree protection report. This information is to be used by planners, architects and designers, in conjunction with any planning controls and other legislation, to develop the design layout in such a way that trees selected for retention are provided with enough space. The report should list all the trees, providing all the details collected in the tree assessment (see Clause 2.3.2). Trees (or groups of trees) should be placed into categories based on their suitability for retention (for examples refer to documents listed in Appendix E). Trees suitable for retention should be identified and marked on the detailed survey plan. This plan should also show the location of TPZs, trees to be transplanted and trees to be removed. TPZs are to be calculated as shown in Section 3. 2.3.4 Development design and review The preliminary arboricultural report should guide the development layout. During the design and documentation stages, the project arborist should be involved in ongoing review of architectural, engineering (e.g. bulk earth works and construction drawings), services and landscape drawings. The purpose of this is to determine the potential impact on trees proposed to be retained. Consideration should be given to tree sensitive measures such as pier and beam, suspended slabs, cantilevered building sections, screw piles and contiguous piling. Service corridors should be established at the planning stage to avoid their redirection after works have commenced. It is essential that detailed plans show the routing of all services (above and below ground) in the proximity of trees. Consideration should be given to acti vities required during the construction stage, such as over-excavation, scaffolding, temporary access roads, stockpiling materials, site sheds, temporary services and sediment control measures as well as the permanent elements of the development such as onsite water detention and storage. 2.3.5 Arboricultural impact assessment The arboricultural impact assessment will be prepared once the final layout is complete. The report will identify trees to be removed, retained or transplanted. The report will identify possible impacts on trees to be retained. The report will explain design and construction methods proposed to minimize impacts on retained trees where there is encroachment into the calculated TPZ (refer to Clause 3.3.2). It will recommend measures necessary to protect the trees throughout all demolition and construction stages. Review of architectural, services and landscape plans should be included to provide an accurate impact assessment. If these plans are not available for review, it should be clearly stated in the report. Specification of tree protection measures will be included in construction documentation (refer to Section 4). The report will include a tree protection plan (drawing) showing the TPZs for trees being retained taking into account the matters referred to in Section 3 and other protection measures. Groups of trees with overlapping TPZs may be included within a single protection area. A copy of this plan will form part of the development plans. The tree protection plan should be included in subsequent construction documentation. The location of tree protection measures should also be shown on other documents such as demolition, bulk earth works, construction and landscape plans. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 14 11 AS 4970—2009 www.standards.org.au © Standards Australia SECTION 3 DETERMINING THE PROTECTION ZONES OF THE SELECTED TREES 3.1 TREE PROTECTION ZONE (TPZ) The tree protection zone (TPZ) is the principal means of protecting trees on development sites. The TPZ is a combination of the root area and crown area requiring protection. It is an area isolated from construction disturbance, so that the tree remains viable. The TPZ incorporates the structural root zone (SRZ) (refer to Clause 3.3.5). 3.2 DETERMINING THE TPZ The radius of the TPZ is calculated for each tree by multiplying its DBH × 12. TPZ = DBH × 12 where DBH = trunk diameter measured at 1.4 m above ground Radius is measured from the centre of the stem at ground level. A TPZ should not be less than 2 m nor greater than 15 m (except where crown protection is required). Clause 3.3 covers variations to the TPZ. The TPZ of palms, other monocots, cycads and tree ferns should not be less than 1 m outside the crown projection. 3.3 VARIATIONS TO THE TPZ 3.3.1 General It may be possible to encroach into or make variations to the standard TPZ. Encroachment includes excavation, compacted fill and machine trenching. 3.3.2 Minor encroachment If the proposed encroachment is less than 10% of the area of the TPZ and is outside the SRZ (see Clause 3.3.5), detailed root investigations should not be required. The area lost to this encroachment should be compensated for elsewhere and contiguous with the TPZ. Variations must be made by the project arborist considering relevant factors listed in Clause 3.3.4. The figures in Appendix D demonstrate some examples of possible encroachment into the TPZ up to 10% of the area. 3.3.3 Major encroachment If the proposed encroachment is greater than 10% of the TPZ or inside the SRZ (see Clause 3.3.5), the project arborist must demonstrate that the tree(s) would remain viable. The area lost to this encroachment should be compensated for elsewhere and contiguous with the TPZ. This may require root investigation by non-destructive methods and consideration of relevant factors listed in Clause 3.3.4. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 15 AS 4970—2009 12 © Standards Australia www.standards.org.au 3.3.4 TPZ encroachment considerations When determining the potential impacts of encroachment into the TPZ, the project arborist should consider the following: (a) Location and distribution of the roots to be determined through non-destructive investigation methods (pneumatic, hydraulic, hand d igging or ground penetr ating radar). Photographs should be taken and a root zone map prepared. NOTE: Regardless of the method, roots must not be cut, bruised or frayed during the process. It is imperative that exposed roots are kept moist and the excavation back filled as soon as possible. (b) The potential loss of root mass resulting from the encroachment: number and size of roots. (c) Tree species and tolerance to root disturbance. (d) Age, vigour and size of the tree. (e) Lean and stability of the tree. NOTE: Roots on the tension side are likely to be most important for supporting the tree and are likely to extend for a greater distance. (f) Soil characteristics and volume, topography and drainage. (g) The presence of existing or past structures or obstacles affecting root growth. (h) Design factors. Tree sensitive constru ction measures such as pier and beam, suspended slabs, cantilevered building sections, screw piles and contiguous piling can minimize the impact of encroachment. When siting a structure near to a tree, the future growth of the tree, both above and below ground should be taken into account. Precautions should be taken at the planning and design stage to minimize potential conflict between trees and new structures. When the root zone is reactive clay, techniques such as localized pier and beam (bridged), screwpile footings or root and soil moisture control barriers may be appropriate to minimize effects on structures. NOTE: Collaboration may be required between the project arborist and the geotechnical or structural engineer. Further information is provided in the documents listed in Appendix E. 3.3.5 Structural root zone (SRZ) The SRZ is the area required for tree stability. A larger area is required to maintain a viable tree. The SRZ only needs to be calculated when major encroachment into a TPZ is proposed. There are many factors that affect the size of the SRZ (e.g. tree height, crown area, soil type, soil moisture). The SRZ may also be influenced by natural or built structures, such as rocks and footings. An indicative SRZ radius can be determined from the trunk diameter measured immediately above the root buttress using the following formula or Figure 1. Root investigation may provide more information on the extent of these roots. SRZ radius = ( D × 50) 0.42 × 0.64 where D = trunk diameter, in m, measured above the root buttress NOTE: The SRZ for trees with trunk diameters less than 0.15 m will be 1.5 m (see Figure 1). Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 16 13 AS 4970—2009 www.standards.org.au © Standards Australia STEM DIAMETER (D), m RSRZ STRUCTURAL ROOT ZONE RADIUS, m The curve can be expressed by the following formula: RSRZ = (D x 50) 0.42 × 0.64 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 SRZ radius D NOTES: 1 R SRZ is the calculated structural root zone radius (SRZ radius). 2 D is the stem diameter measured immediately above root buttress. 3 The R SRZ for trees less than 0.15 m diameter is 1.5 m. 4 The R SRZ formula and graph do not apply to palms, other monocots, cycads and tree ferns. 5 This does not apply to trees with an asymmetrical root plate. FIGURE 1 STRUCTURAL ROOT ZONE CALCULATION 3.3.6 Crown protection Tree crowns may be injured by machinery such as excavators, drilling rigs, cranes, trucks, hoarding installation and scaffolding. The TPZ may need to include additional protection of the above ground parts of the tree. Where crown protection is required, it will usually be located at least one metre outside the perimeter of the crown (see Figure 2). The erection of scaffolding may require an additional setback from the edge of the crown. Crown protection may include pruning, tying-back of branches or other measures. If pruning is required, requirements are specified in AS 4373 and should be undertaken before the establishment of the TPZ. NOTE: Pruning may require approval from the determining authority. A1 Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 17 AS 4970—2009 14 © Standards Australia www.standards.org.au TPZ TPZ SRZ SRZ SRZ TPZ TPZ SRZ SRZ Crown Crown Plan view Elevation view Plan view Tree protection zone Tree protection zone adjusted to include crown protection Elevation view Crown TPZ SRZ Crown TPZ NOTE: Refer to Clause 3.2 for calculation of TPZ. FIGURE 2 INDICATIVE TREE PROTECTION ZONE Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 18 15 AS 4970—2009 www.standards.org.au © Standards Australia SECTION 4 TREE PROTECTION MEASURES 4.1 GENERAL Tree protection measures include a range of activities and structures. Structures are used to identify and isolate the TPZ (refer to Section 3). These measures are identified in the arboricultural impact assessment and tree protection plan. The TPZ is a restricted area usually delineated by protective fencing (or use of an existing structure such as an existing fence or wall). It is installed prior to site establishment and retained intact until completion of the works. Some works and activities within the TPZ may be authorized by the determining authority. These must be supervised by the project arborist. Any additional encroachment that becomes necessary as the site works progress must be reviewed by the project arborist and be acceptable to the determining authority before being carried out. Approved tree removal and pruning should be carried out before the installation of tree protection measures. 4.2 ACTIVITIES RESTRICTED WITHIN THE TPZ Activities generally excluded from the TPZ include but are not limited to— (a) machine excavation including trenching; (b) excavation for silt fencing; (c) cultivation; (d) storage; (e) preparation of chemicals, including preparation of cement products; (f) parking of vehicles and plant; (g) refuelling; (h) dumping of waste; (i) wash down and cleaning of equipment; (j) placement of fill; (k) lighting of fires; (l) soil level changes; (m) temporary or permanent installation of utilities and signs, and (n) physical damage to the tree. 4.3 PROTECTIVE FENCING Fencing should be erected before any machinery or materials are brought onto the site and before the commencement of works including demolition. Once erected, protective fencing must not be removed or altered without approval by the project arborist. The TPZ should be secured to restrict access. AS 4687 specifies applicable fencing requirements. Shade cloth or similar should be attached to reduce the transport of dust, other particulate matter and liquids into the protected area. Fence posts and supports should h ave a diam eter greater than 20 mm and be located clear of roots. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 19 AS 4970—2009 16 © Standards Australia www.standards.org.au Existing perimeter fencing and other structures may be suitable as part of the protective fencing. Figure 3 indicates an example of protective fencing. 4.4 SIGNS Signs identifying the TPZ should be placed around the edge of the TPZ and be visible from within the development site (refer Figure 3). The lettering on the sign should comply with AS 1319. Appendix C provides an example of a suitable TPZ sign. 13 2 1.8 m 4 LEGEND: 1 Chain wire mesh panels with shade cloth (if required) attached, held in place with concrete feet. 2 Alternative plywood or wooden paling fence panels. This fencing material also prevents building materials or soil entering the TPZ. 3 Mulch installation across surface of TPZ (at the discretion of the project arborist). No excavation, construction activity, grade changes, surface treatment or storage of materials of any kind is permitted within the TPZ. 4 Bracing is permissible within the TPZ. Installation of supports should avoid damaging roots. FIGURE 3 PROTECTIVE FENCING 4.5 OTHER TREE PROTECTION MEASURES 4.5.1 General When tree protection fencing cannot be installed or requires temporary removal, other tree protection measures should be used, including those set out below. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 20 17 AS 4970—2009 www.standards.org.au © Standards Australia 4.5.2 Trunk and branch protection Where necessary, install protection to the trunk and branches of trees as shown in Figure 4. The materials and positioning of protection are to be specified by the project arborist. A minimum height of 2 m is recommended. Do not attach temporary powerlines, stays, guys and the like to the tree. Do not dr ive n ails into the trunks or branches. 4.5.3 Ground protection If temporary access for machinery is required within the TPZ ground protection measures will be required. The purpose of ground protection is to prevent root dam age and soil compaction within the TPZ. Measures may include a permeable membrane such as geotextile fabric beneath a layer of mulch or crushed rock below rumble boards as per Figure 4. These measures may be applied to root zones beyond the TPZ. Padding Geotextile membrane underneath mulch or aggregate Trunk protection (battens strapped together) Branch protection Steel plates or equivalent with or without mulch Rumble boards strapped over mulch or aggregate Padding 100 mm of mulch NOTES: 1 For trunk and branch protection use boards and padding that will prevent damage to bark. Boards are to be strapped to trees, not nailed or screwed. 2 Rumble boards should be of a suitable thickness to prevent soil compaction and root damage. FIGURE 4 EXAMPLES OF TRUNK, BRANCH AND GROUND PROTECTION Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 21 AS 4970—2009 18 © Standards Australia www.standards.org.au 4.5.4 Root protection during works within the TPZ Some approved works within the TPZ, such as regrading, installation of piers or landscaping may have the potential to damage roots. If the grade is to be raised the material should be coarser or more porous than the underlying material. Depth and compaction should be minimized. Manual excavation should be carried out under the supervision of the project arborist to identify roots critical to tree stability. Relocation or redesign of works may be required. Where the project arborist identifies roots to be pruned within or at the outer edge of the TPZ, they should be pruned with a final cut to undamaged wood. Pruning cuts should be made with sharp tools such as secateurs, pruners, handsaws or chainsaws. Pruning wounds should not be treated with dressings or paints. It is not acceptable for roots within the TPZ to be ‘pruned’ with machinery such as backhoes or excavators. Where roots within the TPZ are exposed by excavation, temporary root protection should be installed to prevent them drying out. This may include jute mesh or hessian sheeting as multiple layers over exposed roots and excavated soil profile, extending to the full depth of the root zone. Root protection sheeting should be pegged in place and kept moist during the period that the root zone is exposed. Other excavation works in proximity to trees, including landscape works such as paving, irrigation and planting can adversely affect root systems. S eek ad vice from the project arborist. 4.5.5 Installing underground services within TPZ All services should be routed outside the TPZ. If underground services must be routed within the TPZ, they should be installed by directional drilling or in manually excavated trenches. The directional drilling bore should be at least 600 mm deep. The project arborist should assess the likely impacts of boring and bore pits on retained trees. For manual excavation of trenches the project arborist should advise on roots to be retained and should monitor the works. Manual excavation may include the use of pneumatic and hydraulic tools. Refer Clause 4.5.3. 4.5.6 Scaffolding Where scaffolding is required it should be erected outside the TPZ. Where it is essential for scaffolding to be erected within the TPZ, branch removal should be minimized. This can be achieved by designing scaffolding to avoid branches or tying back branches. Where pruning is unavoidable it must be specified by the project arborist in accordance with AS 4373. NOTE: Pruning works may require approval by determining authority. Ground below the scaffolding should be protected by boarding (e.g. scaffold board or plywood sheeting) as shown in Figure 5. Where access is required, a board walk or other surface material should be installed to minimize soil compaction. Boarding should be placed over a layer of mulch and impervious sheeting to prevent soil contamination. The boarding should be left in place until the scaffolding is removed. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 22 19 AS 4970—2009 www.standards.org.au © Standards Australia Tree protection zone (TPZ) Geotextile fabric Mulch max. 100 mm min. 50 mm Scaffold planks Soleplate over geotextile. No excavation for soleplate within TPZ Type A or Type B hoarding. Minimum 1800 high Temporary fence may be incorporated into scaffolding as containment screening or as hoarding Boards or plywood to be installed over mulch for any access areas within the TPZ Branches may require pruning to erect scaffolding. Flexible branches should be tied back rather than pruned. Pruning may be subject to local regulations NOTE: Excavation required for the insertion of support posts for tree protection fencing should not involve the severance of any roots greater than 20 mm in diameter, without the prior approval of the project arborist. FIGURE 5 INDICATIVE SCAFFOLDING WITHIN A TPZ 4.6 MAINTAINING THE TPZ 4.6.1 Mulching The area within the TPZ should be mulched. The mulch must be maintained to a depth of 50–100 mm using material that complies with AS 4454. Where the existing landscape within the TPZ is to remain unaltered (e.g. garden beds or turf) mulch may not be required. 4.6.2 Watering Soil moisture levels should be regularly monitored by the project arborist. Temporary irrigation or watering may be required within the TPZ. An above-ground irrigation system should be installed and maintained by a competent individual. 4.6.3 Weed removal All weeds should be removed by hand without soil disturbance or should be controlled with appropriate use of herbicide. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 23 AS 4970—2009 20 © Standards Australia www.standards.org.au SECTION 5 MONITORING AND CERTIFICATION 5.1 GENERAL There are many stages in the development process from site acquisition to completion where the project arborist is required to monitor or certify tree protection. Table 1 summarizes the process and indicates the stages that normally require certification (a written statement of compliance). This Section provides details of the monitoring and certification process. 5.2 TREE PROTECTION PLAN The approved tree protection plan must be available onsite prior to the commencement of and during works. The tree protection plan will identify key stages where monitoring and certification will be required. A pre-construction meeting should be attended by the site manager, the project arborist and contractors to introduce the tree protection plan and its requirements. 5.3 PRE-CONSTRUCTION 5.3.1 Tree removal and pruning Trees for removal or transplanting should be marked onsite as per the approved tree protection plan. Before removal, the project arborist should confirm that all marked trees correspond with those shown on the schedule or plan. Other tree work may be specified in the tree protection plan. Tree removal should be carried out prior to erection of protection fencing. Contractors should be instructed to avoid damage to trees within protection areas when removing or pruning trees. This may include restrictions of vehicle movements. Any approved pruning required to allow for works should be done at this stage. AS 4373 specifies requirements for pruning. Stumps to be removed from within a TPZ must be removed in a manner that avoids damaging or disturbing roots of trees to be retained. The project arborist should supervise tree removal, transplanting and pruning and certify the works on completion. 5.3.2 Installing tree protection fencing and other protection measures Fencing and other protection measures are to be installed in compliance with Section 4 and as detailed in the tree protection plan. Protection measures are to be certified by the project arborist. 5.4 CONSTRUCTION STAGE 5.4.1 General In order to ensure that protection measures are being adhered to during the pre-construction and construction stages, there should be a predetermined number of site inspections carried out by the project arborist. Matters to be monitored and reported should include tree condition, tree protection measures and impact of site works which may arise from changes to the approved plans. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 24 21 AS 4970—2009 www.standards.org.au © Standards Australia If there is non-compliance with tree protection measures or if trees h ave been damaged, a timeframe for compliance and remedial works should be specified by the project arborist. The determining authority may need to be notified of non-compliance issues. Monitoring, reporting and certification should be carried out at the following critical stages of construction. 5.4.2 Site establishment The project arborist will monitor the impacts of demolition, bulk earth works, installation of temporary infrastructure including bunding, sediment control works and drainage works. The construction management plan (site establishment plan) should be checked for compliance with the tree protection plan. The construction management plan normally includes location of site sheds, stockpile areas, temporary access roads and sediment control devices. At completion of site establishment, the project arborist should certify that tree protection measures comply with the tree protection plan. 5.4.3 Construction work The project arborist will monitor the impacts of general construction works on retained trees. Monitoring should be done at regular intervals or in consultation with the site manager. Monitoring is to be recorded for inclusion in certification at practical completion. Critical stages typically include installation of services, footings and slabs, scaffolding, works within the TPZ and at completion of building works. 5.4.4 Landscape works The landscape plan should be checked for compliance with the tree protection plan. The project arborist may need to approve the staged remo val of pro tection measures required to allow for landscape works. The project arborist should supervise any works within TPZs, including retaining walls, irrigation and lighting installation, topdressing, planting and paving. The project arborist should specify any remedial works above and below ground. Monitoring is to be recorded for inclusion in certification at practical completion. 5.4.5 Practical completion Practical completion assumes that all construction and landscaping works are finished. At practical completion all remaining tree protection measures should be removed. The project arborist should assess tree condition and provide certification of tree protection. 5.5 POST-CONSTRUCTION 5.5.1 Defects liability period Completion of outstanding building or landscaping works following the construction period must not injure trees. 5.5.2 Final certification The project arborist should assess the condition of trees and their growing environment, and make recommendations for any n ecessary remedial actions. Following the final inspection and the completion of any remedial works, the project arborist should certify (as appropriate) that the completed works have been carried out in compliance with the approved plans and specifications for tree protection. Certification should include a statement on the condition of the retained trees, details of any deviations from the approved tree protection measures and their impacts on trees. Copies of monitoring documentation may be required. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 25 AS 4970—2009 22 © Standards Australia www.standards.org.au NOTES: 1 Remedial actions may include pruning in accordance with AS 4373 and/or soil remediation. 2 If the project arborist has not been involved throughout the project, they should have access to inspection reports by others and should review construction drawings to determine likely impacts on trees. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 26 23 AS 4970—2009 www.standards.org.au © Standards Australia APPENDIX A DIAMETER AT BREAST HEIGHT (DBH) (Informative) The diversity of trunk shapes, configurations and growing environments requires that DBH be measured using a range of methods to suit particular situations and Figure A1 provides examples. DBH 1.4 m 4. Tree fork above 1.4 m DBH 6. Tree fork below 1.4 m5. Tree fork at 1.4 m 7. Branch whorls at 1.4 m DBH just above deformity DBH at narrowest point below fork DBH at narrowest point below whorls 8. Tree deformed at 1.4 m DBH just above buttress 9. Buttressed tree DBH 1.4 m 1. Tree on level ground DBH 1.4 m 2. Tree on sloping ground 1.4 m 3. Tree leaning on level ground DBH NOTE: For example 6, the combined stem DBH may be calculated using the formula: 22 2 12 3Total DBH (DBH ) (DBH ) (DBH )=+ + FIGURE A1 MEASUREMENT OF DBH OF A TREE Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 27 AS 4970—2009 24 © Standards Australia www.standards.org.au APPENDIX B POTENTIAL DAMAGE TO TREES ON DEVELOPMENT SITES (Informative) B1 INTRODUCTION Established trees of good vigour and structure represent an asset to any development site, particularly if landscaping is a significant component of the proposed development. Trees may be retained because of their aesthetic features, for shade, for the scale that they will give to new buildings or for their histor ical value. Trees are living organisms that require certain environmental conditions in order to maintain their value as an asset. As remediation of badly stressed or damaged trees is rarely successful, damage must be avoided or minimized during development. Hence, if trees are to be retained and their requirements met, procedures which ensure the protection of trees must be in place at all stages of the development including the demolition stage. B2 BACKGROUND BIOLOGY B2.1 General All plants consist of three main sections: a crown (leaves), a stem or trunk and a root system. Each one of these sections carries out specific functions necessary for the survival of the tree as all of the parts interact. A tree is in a state of physiological equilibrium between the above ground and below ground sections, so that if one of these sections is damaged, the entire tree will suffer and symptoms may appear in any part of the tree. Thus any demolition and construction operations that occur around trees must be carried out in such a way as to minimize the impact on the health of the tree. B2.2 Leaves The main function of leaves is photosynthesis, that is, the production of sugars. The sugars produced by the leaves (and any other green tissue) are the source of chemical energy for all living cells in the entire plant and as such are essential for the normal functioning and survival of the tree. Anything that directly or indirectly damages the leaves will interfere with photosynthesis. B2.3 Trunks and branches Branches and trunks are composed of many tissues with specialized functions including the bark (protection), phloem (transport of sugars from the leaves), vascular cambium (growth of new transport tissues), sapwood (transport of water and nutrients from the roots), heartwood (strength and structural support) and rays (internal transport and storage of sugars). Damage to branches or trunks may allow inf ection by plant pathogens (disease- causing organisms), disrupt the movement of vital materials and structurally weaken the tree. B2.4 Roots The main functions of roots include the upt ake of w ater and nutrients, anchorage, storage of sugar reserves and the production of some plant hormones required by the shoots. In order for roots to function, they must be supplied with oxygen from the soil. The root system of trees consists of several ‘types’ of roots found in different parts of the soil and is generally much more extensive than commonly thought. The importance of roots is easily overlooked because they are not visible, that is ‘out of sight, out of mind’. Damage to the root system is a common cause of tree decline and death and is the most common form of damage associated with development sites. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 28 25 AS 4970—2009 www.standards.org.au © Standards Australia Root growth is opportunistic and takes place wherever the soil environment is favourable. The most limiting factor for root growth is air. A number of studies have indicated that roots are much more extensive than commonly thought. In general roots extend outward from the trunk and occupy irregularly shaped areas 4 to 7 times larger than the projected crown area with an average diameter of two or more times the height of the tree. It is a fallacy that tree roots only extend to the edge of the crown. Root systems consist of three main parts— (a) the structural woody roots (anchorage, storage and transport); (b) lower order roots (anchorage, storage and transport); and (c) non-woody roots (absorption of water and nutrients, extension, synthesis of amino acids and growth regulators) (see Figure B1). In addition to lateral root spread being underestimated, root depth in trees has also been grossly exaggerated. Deep root systems or taproots are the exception rather than the rule. Most roots of most trees are found in the very top of the soil. The vast majority of these roots are small non-woody absorbing roots which grow upward into the very surface layers of the soil and leaf litter. This delicate, non-woody system, because of its proximity to the surface, is very vulnerable to injury. Structural woody roots Lower order roots A Detail A Non-woody roots Trunk Crown Crown projection Non-woody roots Dripline Lower order roots FIGURE B1 STRUCTURE OF A TREE IN A NORMAL GROWING ENVIRONMENT Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 29 AS 4970—2009 26 © Standards Australia www.standards.org.au B3 EFFECTS OF DEVELOPMENT ON TREES B3.1 General All parts of the tree may be damaged by development. Damage to any one part of the tree will affect its functioning as a whole. This Paragraph (B3) considers the possible impact of injury on the functioning of each main section of the tree. This highlights the specific protective measures that need to be undertaken. B3.2 Crown damage The canopy of trees can be directly or indirectly damaged. Indirect damage will occur as a result of trunk and or root damage and will not be discussed here. Usually, foliage may be lost or damaged on development sites by pruning or mechanical injury by trucks, cranes, excavators and so on. The removal of leaves reduces the level of photosynthesis and thus the production of sugars. This in turn reduces the tree’s capacity to function normally and to withstand stresses imposed by a change in its environment. Incorrect techniques of pruning such as lopping or flush cutting may produce wounds that are susceptible to infection by wood decay organisms. Similarly, mechanical damage to branches by machinery, etc. will also create wounds. Trees automatically respond to wounding and in doing so use stored sugars. Any wound places an additional load on trees that will inevitably be stressed during construction. B3.3 Trunk damage Trunks of trees may be wounded mechanically during demolition and construction work. This not only predisposes a tree to potential decay but it also interferes with the transport of water, nutrients and sugars throughout the tree. Serious impacts may structurally weaken the tree. B3.4 Root damage Root damage is the most common cause of damage to trees on development sites. As already mentioned in Paragraph B2.4, roots are far more extensive and closer to the surface than commonly thought. Roots can be damaged in the following ways: (a) Removed during grading, excavation and trenching for foundations services, etc. (b) Mechanically wounded, crushed or torn. (c) Compaction by machinery, storage of materials, and installation of work sheds. (d) Soil buildup. (e) Laying of pavements. (f) Chemical contamination of the soil by solvents, fuel, oil, diesel, herbicides, cement waste, etc. (g) Changes in air levels through changes in drainage patterns. (h) Changes in available water. Apart from the actual removal of roots during excav ation or trenching, soil compaction is one of the major causes of root damage on development sites. Compaction is defined as the loss of large pore spaces (macropores) within the soil with a net loss of total pore space. Macropores are essential for the exchange of gases between the soil air and the atmosphere (aeration) and the removal of excess water from the soil (drainage). Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 30 27 AS 4970—2009 www.standards.org.au © Standards Australia Compaction results from loads or stress forces applied to the soil as well as shear forces. Both foot traffic and vehicle traffic exert both forces on soils. Vehicle traffic may cause significant compaction at depths of 150–200 mm (the area in which most absorbing roots are located). The degree of compaction will depend on weight of vehicles, number of movements, soil moisture levels and clay content. Soil handling, stockp iling and transporting also tend to lead to the breakdown of soil structure and thus to compaction. Vibration as a result of frequent traffic or adjacent construction activities will also compact soils. The effects of compaction include— (i) reduced aeration (oxygen levels decrease and carbon dioxide concentration increases to perhaps toxic levels); (ii) low oxygen levels discourage root growth and thus the uptake of water and nutrients; (iii) reduced infiltration of water into the soil and more run-off; (iv) increased run-off increases soil losses by erosion; (v) low oxygen le vels also lead to chemical changes in the soil which can reduce the availability of some plant nutrients; and (vi) the reduction in the number and diversity of beneficial soil organisms (including mycorrhizal fungi). In summary, the effects of root loss or damage by any means could include— (A) loss of stability if structural woody roots or even lower order woody roots are cut; (B) reduction in water and nutrient uptake; (C) an eventual loss of leaves, reduced photosynthesis and thus sugar production; (D) decay as a result of wounding; and (E) predisposition to soil borne pathogens. It is commonly observed that trees may take many years to decline and eventually die from root damage. B4 CONCLUSIONS The negative impacts of inadequate development design, planning and supervision are cumulative and very difficult to remediate after development is completed. The best way to ensure the long term retention of established trees is to follow the guidelines outlined in this Standard. Additional guidance may be found in the documents listed in Appendix E. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 31 AS 4970—2009 28 © Standards Australia www.standards.org.au APPENDIX C TREE PROTECTION ZONE SIGN EXAMPLE (Informative) A TPZ sign provides clear and readily accessible information to indicate that a TPZ has been established. Figure C1 provides an example of a suitable sign. Tree Protection Zone NO ACCESS Contact: FIGURE C1 TREE PROTECTION ZONE SIGN Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 32 29 AS 4970—2009 www.standards.org.au © Standards Australia APPENDIX D ENCROACHMENT INTO TREE PROTECTION ZONE (Informative) Encroachment into the tree protection zone (TPZ) is sometimes unavoidable. Figure D1 provides examples of TPZ encroachment by area, to assist in reducing the impact of such incursions. Stem Stem Stem Stem Encroachment: up to 10% TPZ area Encroachment: up to 10% TPZ area Encroachment: up to 10% TPZ area Trench Encroachment: up to 10% TPZ area TPZ from formula SRZ TPZ with 10% compensation for encroachment TPZ with 10% compensation for encroachment TPZ from formula SRZ TPZ with 10% compensation for encroachment TPZ with 10% compensation for encroachment TPZ from formula TPZ from formula SRZ SRZ NOTE: Less than 10% TPZ area and outside SRZ. Any loss of TPZ compensated for elsewhere. FIGURE D1 EXAMPLES OF MINOR ENCROACHMENT INTO TPZ Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 33 AS 4970—2009 30 © Standards Australia www.standards.org.au APPENDIX E BIBLIOGRAPHY (Informative) 1 BARRELL, J. (1993), ‘Pre-planning tree surveys: Safe Useful Life Expectancy (SULE) is the natural progression’, Arboricultural Journal: 17 , pp 33–46. 2 BARRELL, J. (2001), ‘SULE: Its use and status in the new millennium’ in Management of Mature Trees proceedings of the 4th NAAA Workshop, Sydney, 2001. 3 CODER, K.D. (1995), ‘Tree quality BMPs for developing wooded areas and protecting residual trees’, in Trees and Building Sites Eds Watson and Neely, International Society of Arboriculture, Savoy, Illinois. 4 COSTELLO, L.R. and JONES, K.S. (2003), Reducing Infrastructure Damage by Tree Root: A Compendium of Strategies Western Chapter of the ISA, California. 5 CRAUL, P.J. (1992), Urban Soil in Landscape Design , John Wiley and Sons, New York. 6 CRAUL, P.J. (1999), Urban Soils: Applications and Practices , John Wiley and Sons, New York. 7 Department of Planning and Community Environment (2001), Tree Technical Manual: City of Palo Alto , City of Palo Alto, California (see also www.city.palo-alto.ca.us/trees). 8 DRAPER, D.B. and RICHARDS, P.A. (2009), Dictionary for Managing Trees in Urban Environments , (IACA) Institute of Australian Consulting Arboriculturists ©, CSIRO Publishing, Melbourne. 9 HARRIS, R.W., CLARK, J.R. and MATHENY, N.P. (2004), Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines , 4th edition, Prentice Hall, New Jersey. 10 HAYES, E. (2001), Evaluating Tree Defects , 2nd edition, Safe trees, Rochester, MN. 11 IACA, (2005), Sustainable Retention Index Value, Institute of Australian Consulting Arboriculturists, www.iaca.org.au 12 International Society of Arboriculture (2008), Glossary of Arboricultural Terms (2nd edition) Champain. 13 LONSDALE, D. (1999), Principles of Tree Hazard Assessment and Management , Forestry Commission, The Stationery Office, London. 14 MATHENY, N.P. and CLARK, J.R. (1994), A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas , Second edition, International Society of Arboriculture, Savoy, Illinois. 15 MATHENY, N.P. and CLARK, J.R. (1998), Trees and Development: A Technical Guide to Preservation of Trees during Land Development , International Society of Arboriculture, Savoy, Illinois. 16 MATTHECK, C. and BRELOER, H. (1994), The Body Language of Trees , Research for Amenity Trees No. 4, The Stationery Office, London. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 34 31 AS 4970—2009 www.standards.org.au © Standards Australia 17 MILLER, N.L., RATHKE, D.M. and JOHNSON, G.R. (1 993), Protecting Trees from Construction Damage: A Homeowner’s Guide , NO-OF-6135-S, Minnesota Extension Service, St. Paul. 18 MORRELL, J.D. (1984), ‘Parkway Tree Augering Specifications’, Journal of Arboriculture 10(5):129–132. 19 WATSON, G.W. and NEELY, D. (Eds) (1994), The Landscape Below Ground , Proceedings of an International Workshop on Tree Root Development in Urban Soils, The International Society of Arboriculture, Savoy, Illinois. 20 WATSON, G.W. and NEELY, D. (Eds) (1998), The Landscape Below Ground 11 , Proceedings of an International Workshop on Tree Root Development in Urban Soils, The International Society of Arboriculture, Savoy, Illinois. 21 WATSON, G.W. (1995), ‘Tree root damage from utility trenching’, in Trees and Building Site , Editors Watson and Neely, International Society of Arboriculture, Savoy, Illinois. 22 WATSON, G.W. and NEELY, D. (Eds) (1995), Trees and Building Sites , Proceedings of an International Conference held in the interests of developing a scientific basis for managing trees in proximity to buildings, The International Society of Arboriculture, Savoy, Illinois. Journal of Arboriculture and Urban Forestry Arborist News Arboricultural Journal Urban Forestry and Urban Greening Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 35 AS 4970—2009 32 AMENDMENT CONTROL SHEET AS 4970—2009 Amendment No. 1 (2010) CORRECTION SUMMARY: This Amendment applies to the Preface and Figure 1. Published on 26 March 2010. Licensed to Standard on 13-Jul-2017. 1 user personal license only. Copying, copy/pasting, storage & distribution or use on network prohibited. Get permission to copy from or network this publication www.saiglobal.com/licensing Page 36 Standards Australia Standards Australia develops Australian Standards® and other documents of public benefit and national interest. These Standards are developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth Government, Standards Australia is recognized as Australia’s peak non-government national standards body. Standards Australia also supports excellence in design and innovation through the Australian Design Awards. For further information visit www.standards.org.au Australian Standards® Committees of experts from industry, governments, consumers and other relevant sectors prepare Australian Standards. 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