Health and Safety Executive Evaluation of current rigging and dismantling practices used in arboriculture Prepared by Treevolution and Brudi & Partner TreeConsult for the Health and Safety Executive and the Forestry Commission 2008 RR668 Research Report Health and Safety Executive Evaluation of current rigging and dismantling practices used in arboriculture Andreas Detter Brudi & Partner TreeConsult Berengariastr 7 82131 Gauting, Germany Chris Cowell Treemagineers Limited Dall Store, Rannoch Station Scotland PH18 5TP Liam McKeown Treevolution Nantgwynant, Beddgelert Gwynedd, North Wales LL55 4NQ Paul Howard ArBO GbR Engelbertstr 15 D-81241 Munich, Germany This report presents the results of a comprehensive study into a number of topics related to rigging operations used in the dismantling of trees in the UK. The information it contains should enable the arboricultural industry to determine good practice in: ■ carrying out risk assessments prior to dismantling a tree; ■ planning and organising rigging operations; and ■ selecting measures to mitigate against risks and accidents. The project received additional funds from the Hyland John’s Grant Programme of the TREE Fund (Grant No 06-HJ-05), in order to extend the investigation on the load-bearing capacity of branches beyond the scope of the original project plan. This report and the work it describes were jointly funded by the Health and Safety Executive (HSE) and the Forestry Commission (FC). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE or FC policy. HSE Books © Crown copyright 2008 First published 2008 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the copyright owner. Applications for reproduction should be made in writing to: Licensing Division, Her Majesty’s Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by e-mail to [email protected] ii ACKNOWLEDGEMENTS This report describes work undertaken by a number of people, principal among them being Andreas Detter (Brudi & Partner TreeConsult, Germany), Chris Cowell (TreePartner, UK), Paul Howard (ArBO, Germany) and Liam McKeown (Treevolution Ltd, UK). However, the work would not have been possible without contributions from many other arborists, consultants and researchers from around the world. Both the pilot study and the present research could not have been undertaken without the support of Erk Brudi and Frank Bischoff (Brudi & Partner TreeConsult, Germany), who provided the initial budget and freed up the time required by their partner to undertake the work. Chapters 1, 3 and 4 represent the results of close collaboration between a number of arborists, with major inputs from Chris Cowell (TreePartner, UK), Richard Allmond and Phil Watkin (both of Treevolution Ltd, UK) and Mark Bridge (Treemagineers, UK), the latter providing the excellent technical illustrations. Dwayne Neustaeter’s work (which provided an introduction to the system of coloured flag indicators) was an inspiration for Chapter 2. Erk Brudi (Brudi & Partner TreeConsult, Germany) improved this chapter by performing a studied and detailed review of its contents. Chapter 6 benefited considerably from previous work on log weights undertaken by Uwe Thomson (Baumpflege Thomsen, Germany) and Klaus Schöpe (Germany), both of whom kindly gave permission for their results to be used. Volker Genenz (Germany) also provided valuable data from his original publication in 1977. Ken Palmer and Michael Tain (ArborMaster Training, USA) provided valuable data to support the work described in Chapter 7, and also provided background information to facilitate the data analysis. Randy Nulle, Rafael Chou and Howard Wright (Samson Rope Technologies, USA) made significant contributions to data collection and evaluation. The rope manufacturers Edelmann & Ridder (Germany) and Teufelberger (Austria) provided laboratory facilities and manpower for rope testing. Dan Pockmann (Bucaneer Ropes) sponsored the project by providing the ropes used in the preliminary laboratory studies and field tests. The field tests described in Chapter 8 were carried out in co-operation with Elisabeth Eberl and Christian Höhne, two students who were in the process of completing courses in the studies of forestry and landscape management respectively (work undertaken in the course of this project formed part of their final submissions). Prof. Peter Glos and Dr. Georg Gaede (Institut für Holzforschung, Munich) provided laboratory facilities, supported the determination of density and moisture content of specimens, and enabled the calibration of the load sensors. Numerous discussions with Ken Palmer (ArborMaster Training, USA), his involvement in the development of the specialist software Rigging 1.0, and the accumulated knowledge base of ArborMaster Training, all provided an essential source of both information and inspiration for Chapter 8. Jens Heinrich (CCC Campus Computer Center) provided the Utilius® EasyInspect computer software free of charge. W. Schröppel (Partner GmbH Baumpflege) sponsored the hydraulic lift used for video recording field tests. The custom-made load sensors were developed with support from Sigmund Glaser (HBM), who also provided data acquisition equipment. Trees were provided courtesy of Deutsche Bundeswehr, Standortverwaltung Fliegerhorst Erding, with the kind permission of Erhardt Worofka (Staatliches Hochbauamt Freising). Mike Neuheimer gave generously of his time and provided numerous helpful suggestions. iii The published work of the late Dr. Peter Donzelli provided particular inspiration to the project. Sharon Lilly donated some of Peter’s unpublished notes that originated from studies of drop tests funded by the TREE Fund’s Hylands John Grant Programme. Ken Palmer (ArborMaster Training, USA) was able to provide video footage and other information to support the notes. The initial studies of the kinematics of rigging operations would not have been possible without the technical input and constant support of Prof. Klaus Schneider (Universität der Bundeswehr, Neubiberg), who provided laboratory facilities, manpower, and support for data evaluation. Dr. Norbert Praxl (DeMotu) aided the understanding of the effects of rigging forces on a climber's body through fruitful discussions and a simulation based on the test data. Paul Howard and Oriol Campaña (ArBO Baumpflege) donated both time and effort. Johannes Bilharz and Erich Rotheimer (Freeworker Baumpflegefachhandel oHG) were always willing to take part in discussions, and supported the project by donating items of arborist equipment. Numerous arborists provided (or gave permission for the use of) drawings, photographs and other illustrations included in the report. Other colleagues and friends supported the work by sharing information and ideas in fruitful discussions, while there were others who helped the project by proof-reading sections of the report and providing comments based on their specific areas of expertise. Phil Watkin and Julia Harding (Treevolution Ltd, UK) shouldered the enormous task of editing the work of numerous authors based in both the UK and Germany. Notwithstanding any previous mentions in these acknowledgements (and with apologies to anyone who has been inadvertently omitted), the authors would especially like to thank: Mark Adams, Richard Allmond, Scott Baker, Edgar Berger, Andreas Born, Mark Bridge, Malcolm Chaffer, Julian Dunster, Mike Greer, Ken James, Professor Heinrich Kreuzinger, Sharon Lilly, Dirk Lingens, Professor Frieder Luz, Guy Meilleur, Thomas Reuschel, Lars Rodrigues, Wolfgang Scholz and Professor Hanns-Christof Spatz. Finally, Frances Hirst, Alison Richards and Val Jones of the Health and Safety Executive, and, last but not least, James Dewar of the Forestry Commission, must all be thanked for the co­ operation, enthusiasm and patience that they displayed throughout the course of the project. iv CONTENTS ACKNOWLEDGEMENTS iii EXECUTIVE SUMMARY 1 INTRODUCTION 9 1 MANAGING A RIGGING OPERATION 13 1.1 Responsible and competent persons 13 1.2 Off-site preparations 14 1.3 On-site preparations 18 1.4 General considerations 19 2 VISUAL TREE INSPECTION PRIOR TO UNDERTAKING A RIGGING OPERATION 21 2.1 General 21 2.2 Visual inspection 24 2.3 Sources in literature 25 2.4 A methodology for visual tree inspection prior to climbing and rigging 30 2.5 Symptoms for tree-related hazard 33 2.6 Overall strength and structural stability 64 2.7 Wood-decaying fungi 67 2.8 Potential remedial action 69 3 SAFE RIGGING STRATEGY AND SYSTEMS 73 3.1 Establishing a safe strategy 73 3.2 Selecting a rigging technique 75 3.3 Selecting and setting up equipment 77 3.4 Carrying out the operation 79 3.5 Reviewing the operation 86 4 RIGGING HARDWARE, CORDAGE AND TEXTILE COMPONENTS 87 4.1 Hardware components 88 4.2 Cordage and textile components 91 4.3Survey Results 93 4.4 Legislation considerations 94 4.5 General conclusions 97 5 BEARING CAPACITY OF TREE SPECIES 99 5.1 Methods of assessing the load-bearing capacity 99 5.2 Mechanical properties of green stem tissue 100 5.3 Load-bearing charts for stems 105 5.4 Strength loss due to structural defects 110 5.5 Strength of limbs and branches used as anchor points 118 5.6 Anchoring strength of roots 131 5.7 General consideration 132 v 6 ESTIMATING THE WEIGHT