EGL Ref: 8983 23 June 2022 Page 16 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. that the dam and appurtenant structures remain functional and that the resulting damage is minor and easily repairable. SEE (incl. Aftershock): The performance requirement for the SEE is that there is no uncontrolled release of the impounded contents when the dam is subjected to the seismic load imposed by the SEE. Damage to the structure may have occurred. Freeboard • Maximum Normal Reservoir Level Wind set up and wave runup for the highest 10% of waves caused by a sustained wind speed, which is dependent on the fetch, with an AEP of greater than 1 in 100 • Freeboard at Maximum Reservoir Level during the Inflow Design Flood (IDF) The greater of a) 1.0m or b) the sum of the wind setup and wave runup for the highest of waves caused by sustained wind speed, which is dependent on the fetch, within an AEP of 1 in 10 The IDF will be taken equal to the 72-hour PMP flood event. This is based on the recommendations in the NZDSG for High PIC dams where the PLL is greater than 10 and is consistent with the design criteria adopted for the existing Storage 1A and 2. The controlling magnitude earthquake (CME) taken to be an 84th percentile shaking event from a maximum rupture on the Kerepehi Fault System (onshore sections) does not exceed the 1 in 10,000 AEP ground motion developed by a probabilistic approach. In this case under the NZDSG the SEE can be taken to be the 84th percentile for the CME. However, for the design of Storage 3 a second SEE case applying the 1 in 10,000 AEP ground motion has also been applied. For the proposed dam, the wind set up and wave run up are small due to the small fetch. Under normal operation, the pond water is proposed to be maintained 3.0m below the design crest level. Consequently, the 1st criterion controls for freeboard during the IDF. For this situation the NZDSG recommend a minimum freeboard of 1.0 m above the IDF for TSFs. The current design freeboard for Storage 1A and 2 is 1 m and this is to be adopted for the proposed new Storage 3 TSF. 10.2. Uphill diversion drain sizing The uphill diversion drain will be sized for a minimum requirement of a 10 year ARI (Average Recurrence Interval) flow, equal to the existing resource consent conditions (RC971307, RC971309, Condition 4). 10.3. Perimeter drain sizing The perimeter drain will be sized for a minimum requirement of a 10 year ARI flow.
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