Large Seismic Event Mitigation Zachary Mayer May

2 Agenda What Happened Project Goals and Results Timeline of Geotechnical Studies Risk Mitigation Ground Support Standards Geotechnical Modelling Results

& 2011 Seismic Events Jan 6/2009: 3.8 Mn event on 7000L. June 15/2009: 3.1 Mn event on 7500L. Aug 21/2011: 3.2 Mn event on 7500L. Sept 13/2011: 3.8 Mn event on 7000L.

4 Seismic Project Goal and Results Determine what happened Horizontal stress fault slip in pillar. Structure & geometry. Can seismic models reproduce the events? Yes – now have a better understanding. Can we control the events? New mining sequence will not eliminate seismic events, but should reduce maximum magnitude going forward. Can we manage the impact of large events? Yes - New support standards are effective in reducing damage/risk. Additional reinforcement in key areas. Re-entry protocols. Expanded the post-blast closure areas and increased personnel re-entry times.

5 Timeline of Geotechnical Risk Studies and Mitigation Efforts large seismic events

6 Ground Control Experts Involved in Kidd Study ( ) Patrick Andrieux – Itasca Consulting, Sudbury David Beck – Beck Engineering, Australia Wilson Blake – Independent Consultant, USA Richard Brummer – Itasca Consulting, Sudbury John Fedorowich – Itasca Consulting, Sudbury Anneta Forsythe – ex-Kidd/Itasca now Vale, Sudbury John Henning – ex-Kidd now Goldcorp, Timmins Marty Hudyma – Laurentian University, Sudbury Steve McKinnon – Queens University, Kingston Rob Mercer – Knight Piesold, North Bay Brad Simser – Xstrata Nickel, Sudbury Graham Swan – Ex-Falconbridge, Sudbury Erik Westmin – Virginia Tech, USA

7 Geotechnical Risk Studies Additional Mitigation Efforts Geotechnical analysis through detailed stress and structural models by 2 different consultants. Historical sequence modelling back to 2001 to try to re- create and understand events. Displacement model Stress Model Seismic Velocity

8 Risk Mitigation Enhanced support installation from 6000L to 9500L – the PPE of the mine. Re-entry protocols. Expanded the post-blast closure areas and increased personnel re-entry times. Currently shutting down between 2-4 levels for 12+ hours approximately 140 times/year. Revised mining sequence. Revised support standards (lower screen & bolt to floor). Six Sigma project– single-pass “in cycle” enhanced support. Ongoing monitoring for deviation - SMART cable installation in intersections.

9 Geotechnical Risk Studies Additional Mitigation Efforts Forensic data mining looking for correlations. Confirming and adjusting ground support in damaged areas. Additional cable bolting in sensitive areas. Instrumenting more intersections. Investigating new seismic monitoring technology. Passive seismic tomography study. Additional microseismic system upgrades.

10 Damage Comparison 2009 vs Enhanced Support Works After 2009 rockburst: 4 intersections collapsed Drift damaged over hundreds of meters Several areas inaccessible After 2011 rockburst: No intersections collapsed Walls damaged over tens of meters No areas inaccessible 3.8Mn - Jan S 3.8Mn - Sept S Complete collapse of back Failure limited to bottom half of walls

11 Enhanced Support Works XC enhanced support installed XC after 3.8Mn event

L Refuge Station Upgrades

L Ramp Upgrades

14 69-S40 ACC Single-Pass Enhanced Support Installed “In Cycle”

15 Seismic Modelling 8 different mining sequences were modelled to test new mining plans in order to reduce seismic risk. Looked at: Mining in different direction, along strike, vertically.. Options for mining pillars, pillar dimensions, de-stress blasts.. Managing stopes around structure, sequence.. New plan reduces risk by deferring GW stope mining to end of mine life, leaving key pillars intact longer. New mining sequence will not eliminate bursting, but should reduce maximum magnitude in future. Bursting is a response to excavation, and is driven by adjustment of rock mass into mined openings

16 Modelling Results Example Seismic Potential 2013 Original Mining Plan New Mining Plan Red areas represent potential seismic zones

17 Conclusion New technology and tools provided better analysis and planning information. Have modelled that we can do something different - new mining sequence reduces risk. Expert consensus obtained on path forward. Enhanced support is doing it’s job. Expanded re-entry protocols keeping people out of harms way. Questions?