EGL Ref: 9216 22 June 2022 Page 12 File: WAI-983-080-REP-GT-0013_Rev0.docx This report shall only be read in its entirety. Campbell method (Ref. 27) was used to estimate the PAR due to flooding of roads and bridges. The total PAR is assessed to be one for the Sunny Day breach scenario. 12.1.3. Potential Loss of Life The Potential Loss of Life is dependent on many factors, a number of which are related to human behaviour and response under adverse conditions, such as the dam breach scenarios. The Campbell method (Ref. 27) was adopted to assess the Potential Loss of Life for roads and bridges. The estimation of Potential Loss of Life for the Sunny Day breach scenario is summarised in Appendix B. People driving across Baxter Road Bridge are at higher risk due to the limited time of warning in the event of a dam breach. The Potential Loss of Life for the Sunny Day breach scenario is assessed to be zero. 12.1.4. Potential Impact on Residential Dwellings In the Sunny Day breach scenario, no downstream residential dwellings are expected to be affected by the breach flood as their floor levels are above the flood level associated with a Sunny Day breach. The impact of a Sunny Day breach on the residential dwellings is assessed to be minimal, with no inundation predicted. 12.1.5. Potential Impact on Major Infrastructure No critical or major public infrastructure would be affected by the Sunny Day breach flood except for Storage 3 itself. Damage to the Baxter Road Bridge would affect the access to the Waihi Processing Plant and Water Treatment Plant from SH2. However, there are alternative routes of access. Some damage to the road surface and erosion of the shoulder of Baxter Road is anticipated. Significant damage to Storage 3 would occur and it would take more than a year to repair Storage 3. The remediation works would need to ensure the long-term stability and security of the tailings. The impact of a Sunny Day breach on the critical or major infrastructure is assessed to be catastrophic, due to the damage to Storage 3. 12.1.6. Potential Impact on Natural Environment A Sunny Day breach of Storage 3 would result in the release of tailings and pond water carrying sediments into the Ruahorehore Stream and Ohinemuri River. Damage to the natural environment includes introduction of sediment and other contaminants into watercourses and onto the surrounding ground surface and erosion and instability along rivers and streams. Some mobilised tailings and eroded embankment would settle out in the Ruahorehore Stream and would require removal. Some mobilised tailings would deposit in the Ohinemuri River. The damage to the natural environment would be significant but recoverable. Clean up would take up to 12 months. Some people could be affected due to potential contamination of water in the river (e.g., people undertaking recreational activities in the river or taking water from the river to irrigate farmland, gardens or crops).
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