Enlarged Cotter Dam

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GHD was engaged by Icon Water (formerly ACTEW Corporation) as the design partner for the Bulk Water Alliance (BWA), which was formed in May 2008 to design and construct Australia’s third largest concrete gravity dam, the Enlarged Cotter Dam (ECD).

The ECD project was the centrepiece of a comprehensive Water Security Program for the Australian Capital Territory. The project comprised the following components:

  • 87 m high roller-compacted concrete (RCC) gravity dam, with a crest length of 330 m, and RCC Volume 380,000 m3
  • 60 m high dry intake tower incorporated into the upstream face of the dam
  • Reinforced concrete stilling basin and outlet works at the toe of the dam
  • Two zoned earth and rockfill embankment dams, 19 m and 23 m high, on the ridge forming the right abutment of the main dam to retain the enlarged storage

GHD’s Geotechnical Investigations for the ECD were extensive and comprehensive. The results obtained enabled the compilation of a detailed geological model of the dam site, particularly in defining, characterising and kinematically analysing geological faults (crushed and sheared seams and zones) that traverse the dam footprint.

These structures had significant design and construction implications for:

  • Abutment stripping and foundation preparation
  • The dam design including the overall geometry and positioning of monolith joints
  • Rock slope stabilisation
  • The foundation of the intake tower
  • The foundations for the three tower cranes that required positioning on the steep abutment slopes.

The steep one to one valley side slopes provided a significant practical challenge for the investigations, requiring rope access for mapping and helicopter lifts for drill rigs.

A full-time engineering geological team presence, from concept to completion, enabled the BWA to identify and successfully negotiate a range of geological issues, the effects of which would have otherwise created construction difficulties with associated adverse workplace safety, programming and cost impacts.

The enlarged Cotter Dam, the highest RCC Dam in Australia, represents an historic project for the ACT and for Australian Engineering. The magnitude and quality of GHD’s Geotechnical Investigations have been recognised by Engineers Australia (Canberra Division) through their prestigious Engineering Excellence Award 2009, “in recognition of quality and safety outcomes of geotechnical investigations performed for the Enlarged Cotter Dam.”

Dams

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We recognise our clients’ needs for solutions that harness in-depth knowledge with forward thinking to produce innovative, safe and cost-effective outcomes. We have successfully delivered through all methods of project delivery, from the conventional approach to design and construct, alliances and Engineering Procurement and Construction Management (EPCM). 

GHD provides services for the following dam types and appurtenant structures:

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Geology

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GHD's Geology team applies geological principles to the civil engineering, and mining and resources development industries. We work with our clients to deliver tailored solutions that optimise the negotiation of prevailing geological conditions, with the aim of minimising project cost and risk.

Our geological services are fully integrated with the diverse skills base across the GHD network. As an international professional services provider, we deliver the following geology services:

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Geotechnical

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Our services include:

Investigation

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