EGL Ref: 9216 22 June 2022 Page 15 File: WAI-983-080-REP-GT-0013_Rev0.docx This report shall only be read in its entirety. residential houses in this study is based on Graham (1999, Ref. 23), which considers two fundamental factors: 1. Severity of flood; and 2. Warning times. The fatality rates for different conditions are listed in Table 4. The fatality rates for Rainy Day failure are in accordance with those due to dam breach flood as summarised in Table 4. The fatality rates for flood events without dam failure are in accordance with ANCOLD Guidelines (Ref. 24). The incremental Potential Loss of Life due to incremental flooding of residential houses is estimated to be one. Based on the Campbell method (Ref. 27), the incremental Potential Loss of Life due to flooding of bridges and roads is estimated to be one. As a result, the total incremental Potential Loss of Life for the Rainy Day breach scenario is estimated to be two. 12.2.4. Potential Impact on Residential Dwellings In the Rainy Day breach scenario, released pond water and eroded tailings (Process I breach water flood) inundates seven residential dwellings to depths greater than 1.5 m and according to fragility curves produced by NIWA (Ref. 28). These seven houses are in the lower lying areas near to the TSFs and south of the Waihi township, the lower area through the Karangahake Gorge, and lower lying areas adjacent to the stopbanks in the Paeroa township. Of these seven houses only one would have exceed 1.5 m in the natural 1 in 1,000 year flood. 47 residential dwellings are identified as being inundated to depths of between 0.5 m to 1.5 m and these houses would have between moderate to severe degrees of damage. In a natural 1 in 1,000 year flood only six houses are estimated to be inundated with depths between 0.5 m to 1.5 m. The impact of a Rainy Day breach on residential dwellings is assessed to be major. 12.2.5. Potential Impact on Major Infrastructure The critical infrastructure affected by the Rainy Day breach scenario modelling include Storage 3, SH2, and the Ohinemuri River stopbanks around Paeroa township. Significant damage of Storage 3 can be anticipated. If the dam failed, it could take more than a year to repair Storage 3. However, Storage 3 may not be the only operating TSF at the Waihi operation. The remediation works would need to ensure the long-term stability and security of the remaining tailings. The SH2 Tauranga Road Bridge in Waihi and Criterion Bridge (on the road from Paeroa to Te Aroha) in Paeroa are indicated to be overtopped by a 1 in 1,000 year flood, and therefore also the same flood with a breach, but damage is estimated to be limited. The Baxter Road Bridge, Waikino Railway Bridge, and Waitawheta Road Bridge are indicated to be overtopped by a 1 in 1,000 year flood, and therefore also the same flood with a breach, and could be destroyed. A significant section of SH2 from Waihi to Paeroa townships would be flooded in 1 in 1,000 year flood and therefore also from a breach. The maximum flood depth and flood velocity varies along SH2. Significant damage would be expected at some locations with large flood depths and velocities (e.g., damage to the road surface, shoulder, and culverts), however,
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