Arnold Dam Strengthening Project

CLIENT

Trustpower (now Contact Energy)

LOCATION

Arnold River, West Coast

RILEY TEAM

Paul Rivett, Don Tate, Titus Smith, Jacob Couprie

THE BRIEF

The Arnold Dam strengthening project supports the long-term resilience of one of New Zealand’s historic hydro-electric assets. The works were designed to enhance seismic performance, improve embankment stability, and safeguard future operation.

This major upgrade to the Arnold Hydro-Electric Power Scheme, was delivered while maintaining generation throughout construction. Key challenges included embankment stability risks during earthquakes, piping and erosion concerns, flood sensitivity, complex foundation conditions, and limited ability to lower reservoir levels.

THE OUTCOME

The solution involved strengthening an 80m concrete core earth embankment, installing a full-height filter and drainage system, building a large downstream earthfill buttress, and upgrading spillway retaining structures.

The project delivered a modern, resilient dam that meets current safety guidelines. It significantly improved embankment stability under seismic and flood loading, eliminated piping risks, and enhanced the reliability of spillway and retaining structures. These works addressed all safety concerns, secured the ongoing operation of the Arnold Hydro-Electric Power Scheme, and preserved its historical legacy.

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