Lower Clutha power investigations : engineering geological feasibility assessment of the proposed Tuapeka Mouth damsite

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Macfarlane, D.F. 1986 Lower Clutha power investigations : engineering geological feasibility assessment of the proposed Tuapeka Mouth damsite. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 402 57 p.

Abstract: Engineering geological investigations have been undertaken to assess the feasibility of constructing a dam/powerhouse complex at Tuapeka Mouth. The investigations indicate that the site will be suitable for a concrete gravity dam, or for an earth or rockfill dam. Downstream sliding of shear-controlled wedges in the foundation rock is considered a slight possibility, requiring further investigation. There is some potential for instability of existing landslides along the reservoir (high level option) upstream from Beaumont and further stability analyses are ecommended for these, in particular under earthquake conditions. No Late Quaternary fault traces are known within 20 km of the proposed damsite and the seismotectonic hazard is assessed as low. However MMVII intensity shaking with peak ground accelerations of up to 0.3 g vertical and 0.2 g horizontal should be anticipated within the design life of the structure. Construction materials are readily available within a few km of the site area but gravel volumes are limited. Although sufficient gravel could be won from the river to allow construction of any of the concrete dam options, the available gravel volumes would be marginal in terms of Scheme B requirements and would be insufficient for earth dam construction. Quarried rock would be available as an alternative and it is recommended that consideration be given to a rockfill dam for the high level (Scheme B) development option. (auth)