EGL Ref: 9216 22 June 2022 Page 14 File: WAI-983-080-REP-GT-0013_Rev0.docx This report shall only be read in its entirety. are shown in Figures C2 and C3 in Appendix C. The extent of the 1 in 1,000 year flood without the dam breach flow is shown as a red line for comparison and to assist judgement of the incremental effects of a breach. The volume of mobilised tailings discharged in Process I is about 0.786 Mm3. The scenario which results in the greatest incremental consequences for the Rainy Day scenario is a breach into a 1 in 1,000 AEP flood event in the Ohinemuri River. A notable contribution to the PIC is the estimated incremental effects on the Paeroa township. Stopbanks along the Ohinemuri River are constructed around Paeroa to provide flood protection (Ref. 25). A sensitivity analysis shows that the 1 in 1,000 AEP flood would be close to the crest of the stopbanks and the Rainy Day breach flow modelled for Storage 3 indicates overtopping of the stopbanks and some shallow flooding of a part of Paeroa township. However, it is reinforced that a 1 in 1,000 year flood and a breach is very unlikely. Some incremental flooding effects could also along the Ruahorehore Stream and Ohinemuri River flood channel including along the southern edge of Waihi township, River Road and SH2 in the Karangahake Gorge, and farmland adjacent to Storage 3. 12.2.2. Population at Risk The assessment of PAR for the Rainy Day breach scenario is summarised in Appendix C. Most of the incremental PAR associated with breach are due to flooding of residential houses and SH2. Residential houses with the greatest incremental effects are located: 1. Along the southern edge of the Waihi township; and 2. Around the northern bank of the Ohinemuri River in the Paeroa township. The incremental PAR due to breach related flooding of residential houses is estimated to be 196. The section of SH2 from Waihi to Tauranga would be flooded over a section of 0.4 km in length by the natural flood, and therefore also the breach flow. The monitored annual average daily traffic (AADT) for this road in 2019 is 11,770 (Ref. 26). SH2 from Waihi to Paeroa would be flooded over a length of 9.3 km by the natural flood, and therefore also the breach flow. However in a major flood, this road would be closed to traffic. The section of SH2 passing Paeroa would be flooded over a section of 0.4 km in length, along withThorp Street and Willoughby Street by the breach flow (>0.5m depth). Several rural roads, i.e., Baxter Road, Clarke Street, Gilmour Street, Frankton Road, are flooded and five bridges are overtopped in the assessment. The Campbell method (Ref. 27) was employed to estimate the PAR due to flooding of roads and bridges. The incremental PAR due to flooding of roads and bridges is estimated to be 4. The combined total incremental PAR (houses, roads, and bridges) assessed for the Rainy Day breach scenario is 200. 12.2.3. Potential Loss of Life The assessment of Potential Loss of Life for the Rainy Day breach scenario is summarised in Appendix C. The assessment of Potential Loss of Life for
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