Dam design and safety

The Dam will be a concrete-face rock fill dam. A rock fill dam is a very stable structure that reuses indigenous material excavated from the site and is appropriate for absorbing seismic loads. The Waimea Community Dam will be approximately 53m high, 220m long and 6m wide at the crest. About 430,000m3 of rock will be used to build the dam or be recycled on site. The reservoir lake created by the dam will contain approximately 13.4 million cubic metres of water.

The Waimea Community Dam is designed to the latest international design standards under the NZ Dam Safety Guidelines and has been and continues to be peer reviewed by technical experts.

Design Parameters

  • 13Mm3 (13 billion litre) reservoir; 53m high; 220m crest length; 430,000m3 rock
  • Rockfill embankment selected as most robust to seismic loads and uses indigenous material
  • Concrete face membrane
  • Zoning of material in embankment allows for drainage paths to mitigate internal erosion
  • Grout curtain seals water migration around and beneath dam
  • Operating basis: No non-superficial damage and fully operational: 1:150 AEP (years)
  • Seismic evaluation basis: Retain reservoir contents: 1:10,000 AEP (years)
  • GNS seismic assessment: 0.64g horizontal peak & 1.65g maximum spectral accelerations
  • Active faults 8km and 12km from site
  • Probable maximum flood (PMF): 1094 m3/s (18.6 Mm3 / 24 hour)
  • 100 year flood: 375 m3/s
  • 12 May 2019 1:50 year 250 m3/s (47 mm/hr)
Operational flow
  • Operational flow: 2.2m3/s
  • Environmental (min) flow and flushing flow: 0.5 m3/s and 5 m3/s
  • Maximum: 17 m3/s (1.5 mM3/d = 10% reservoir / day)

Design Standards: NZSOLD / ANCOLD / ICOLD: Highest category (High PIC)