The Larner-Johnson needle valve. Four of these were installed in 1958.
The design was complex and required a complicated set of operational procedures
to open and close the valve. They had reached the end of their practical working
life and were replaced by the butterfly valves in 2005.
Water drawn through the outlets in the upstream face of the dam travels through any of four valve sets and into the water supply pipelines.
The valves are used to 'turn off' water from the dam during pipeline maintenance or in an emergency.
Each set consisted of a 32.5 tonne central needle valve with a gate valve at each end.
The original valves were replaced by new, more efficient Erhard butterfly type valves made in Germany. The valve replacement project, part of ongoing asset maintenance and upgrade work, began in 2004 and was completed in 2006 at a cost of $10 million.
Installing the original valves in 1958.
Removing the last of the old needle valves in 2005.
New Erhard self closing butterfly valves installed in 2005.