The No. 2 and No. 4 concrete arch dams are an integral part of the Waipori Hydroelectric Power Scheme in Dunedin. Manawa Energy engaged Riley and others to help with technical inputs on assessing the dams’ stability and analysing potential failure modes and effects. 

We undertook the following:

• dam break assessment

• geological mapping

• geotechnical investigation

• erodibility assessments

• rock anchor designs.

Riley worked collaboratively with structural engineers and provided hydrological and geotechnical inputs into the dam stability assessment. 

We facilitated and contributed to the potential failure mode assessment, helping to manage and supervise remedial works including input to the consent stage.

 THE OUTCOME 

The structural analysis found the upper portion of the Waipori No.2 Dam was unstable under seismic loading. That portion had been added to raise the structure after construction.

Manawa Energy opted to remove the upper portion of the dam to improve the safety and stability of the structure.