Report of the inquest into the deaths arising from the Thredbo landslide Derrick Hand Coroner 29 June 2000 Table of contents Table of contents .......................................................................................................................... 1 Table of abbreviations.................................................................................................................. 4 Summary ................................................................................................... 5 Introduction.............................................................................................. 8 The Landslide ................................................................................................................................ 8 Scope of the Report...................................................................................................................... 9 Submissions on Cause................................................................................................................10 Consideration of Cause Submissions.......................................................................................11 Hindsight......................................................................................................................................13 The Course of the Inquest.........................................................................................................14 Presentation of Technical Evidence ........................................................................................14 The Convocation of Engineers.................................................................................................15 Section 33.....................................................................................................................................17 Indictable Offence......................................................................................................................18 Legislative Framework ...............................................................................................................18 A Cautionary Note......................................................................................................................18 The Alpine Way .......................................................................................21 Responsibility for the Alpine Way............................................................................................22 Historical Understanding of Landslide Risk...........................................................................23 History of Landslides along the Alpine Way ..........................................................................25 The Winterhaus Landslide.........................................................................................................26 Status of the Alpine Way before 1968.....................................................................................32 Tyrola Lodge................................................................................................................................33 Relationship between NPWS and the DMR ..........................................................................39 The Bright Period .......................................................................................................................48 RTA as Technical Advisor, 1991-1996 .....................................................57 Arrival of Mr. Tony Sullivan .....................................................................................................57 Mr. Warren-Gash........................................................................................................................59 The Site Inspection.....................................................................................................................60 Subsequent Inspections and Reports.......................................................................................62 Unpredicted Slides......................................................................................................................63 Mr. Reedy’s Supervision.............................................................................................................64 Presence of the Watermain .......................................................................................................65 Approach to Instability Assessment.........................................................................................65 The RTA Slope Risk Assessment.............................................................................................67 Submissions for Mr. Warren-Gash and RTA .........................................................................68 The Development of Thredbo.................................................................71 Identification of Instability in the Eastern Subdivision ........................................................72 The Lend Lease takeover...........................................................................................................75 Construction of Carinya Lodge ................................................................................................80 Regulation of Building in the Park...........................................................................................82 The Dagger Period .....................................................................................................................84 Western Subdivision...................................................................................................................88 Conclusion ...................................................................................................................................89 The Watermain — Construction.............................................................93 1 Construction of the Watermain................................................................................................ 96 Configuration of the Schuss Bend ........................................................................................... 98 Thrust Blocks .............................................................................................................................. 99 Suitability of Watermain Site................................................................................................... 100 The Winterhaus Retaining Wall — Construction .................................111 Purpose of the Retaining Wall................................................................................................ 111 Preliminary Design and Investigations.................................................................................. 111 The Final Design ...................................................................................................................... 112 Construction of the Retaining Wall ....................................................................................... 114 Absence of a Geotechnical Study .......................................................................................... 115 Method of Construction.......................................................................................................... 116 Floor of the Trench.................................................................................................................. 116 Engineering Cause ................................................................................ 119 Slope Failure.............................................................................................................................. 121 Description of the Manner of Failure of the Slope............................................................. 121 Nature of the Landslide Site ................................................................................................... 122 Primary Landslide..................................................................................................................... 123 Two Major Fills on the Site..................................................................................................... 124 Geohydrological Description of the Carinya Site Pre-slide................................................ 124 Change Necessary to Cause the Slide.................................................................................... 125 Nature of the Landslide........................................................................................................... 125 The Watermain Theory ......................................................................... 127 Observations after the Landslide ........................................................................................... 128 Observations prior to the Landslide...................................................................................... 133 Mr. O’Reilly’s Observations.................................................................................................... 133 Water Observations in and around Carinya prior to the Landslide.................................. 136 Observations of water around Carinya.................................................................................. 137 Noises heard prior to the Landslide....................................................................................... 138 Creep .......................................................................................................................................... 138 Rate of Leak .............................................................................................................................