The grand old dame of the Waitaki hydro electricity generation system is undergoing its biggest makeover - at 80 years old.
Meridian Energy Ltd, the owner of the Waitaki Dam and power house, is spending about $41 million - almost 10 times the original $4.6 million cost - refurbishing them, including removing, fixing, then reinstalling one of the generators, which failed in 1998.
Even the small but intricately wooden-panelled lift from the powerhouse to the offices has undergone an overhaul.
The Waitaki Dam project, now about halfway through a four-year programme, was part of Meridian's refurbishment of its power stations, strategic assets manager Richard Griffiths said.
That started with Aviemore, followed by Manapouri and Benmore.
After Waitaki, the company will look at Ohau A, B and C on the upper Waitaki scheme, which will be done together because all were similar when built in the 1970s and 1980s.
The 80th anniversary of Waitaki's official opening was celebrated last month and this project is the biggest refurbishment since it was built.
It originally had two generators, then others were added in 1949 and 1954, when the powerhouse was also lengthened.
Equipment and the construction itself has stood up well to 80 years of use, the two original generators still operating at close to original output, and other equipment and structures still checking out after drilling for earthquake strengthing to modern dam standards.
''Even though it dates back to the 1930s and old pick and shovel construction, it is very well built,'' Mr Griffiths said.
The upgrade being carried out would enable the dam to continue to provide sustainable electricity reliably for many generations to come.
A wide range of work is being carried out, not only on the dam and powerhouse, but also the surrounding structure.
Some of it is huge - for example, repairing and refurbishing generator three, which seized up in 1998 and was not considered economic to repair then, because six were used at any one time.
They run almost continuously, producing a base load to meet New Zealand electricity demand and to ensure the dam meets its minimum flow obligations under its resource consents.
In one of the biggest jobs, the generator has been removed from its pit, including the rotor which weighs close to 120 tonnes.
Once it is reinstalled, it will provide back-up if one of the other generators fails and needs to be overhauled.
The others, including the original two installed in the 1930s, would eventually need upgrading, but with generator three available as back-up, that could be left until the work was necessary.
''It's significant work, as much as $90 million, so we don't want to spend the money too soon,'' Mr Griffiths said.
That made the Waitaki Dam ''real unique'' because it had that spare generator.
The two 1930s generators have been stripped, cleaned, had minor repairs and been realigned, but needed surprisingly little work considering their age.
Also, all the generators will have their electrical protection safety systems upgraded.
Two auxiliary machines, in a pit at the northern end of the power house, have been removed and their penstocks blocked with concrete.
The carbon dioxide fire extinguisher system, which is dangerous to staff, is being replaced with inergen gas units, a safer option.
Changes are also being made to the powerhouse and its roof to ensure it meets the standards requiring it to withstand a one-in-2500-year earthquake.
The mobile crane which runs the length of the powerhouse has a new motor drive, upgraded electrics and a wireless remote control so it can be operated by one person instead of two.
In a nod to modern times, the crane's posted 120 imperial ton limit has been changed to the modern metric equivalent of 121.925 tonnes.
Another major job has been erosion protection on the jetty which juts out at the end of the powerhouse to separate the spillway and the outlets for the penstocks.
Over the past 80 years, water flow had undercut it.
Holes were drilled and lined with pipes that would be filled with concrete to provide long-term protection.
The surface of the jetty would be re-concreted.
Getting the crane in for that work was an intricate job as the access was narrow and it took about three months before the crane was assembled.
Erosion protection on the south bank, below the powerhouse, to protect Transpower's substation has been improved with rock quarried from the Waimate Gorge.
Rock has also been stored for ongoing maintenance of the protection works.
Inside the concrete dam, earthquake protection work is being done and uplift drainage improved to reduce pressure on the dam floor.
At its northern end, a concrete protection wall will undergo earthquake strengthening.
Other work has included replacing the grilles which stop debris entering the penstocks with longer-lasting ones and improving the strength of the spillway gates mechanism.
The access to the dam from State Highway 83 has been improved to New Zealand Transport Agency standards, partly because of the traffic created by the upgrade.
However, once finished, most of the work, except the new entry and security fence, will be invisible to those passing by on SH83.
Waitaki Dam
• Original cost $4.6 million.
• Construction started 1928.
• 1000 to 1200 workers.
• Last NZ dam built by pick, shovel and wheelbarrow.
• Dam 48m high and 542m long.
• Powerhouse 150m long with 7 generators.
• Officially opened October 27, 1934.
• Electricity generation started 1935.
• Two 15MW generators commissioned 1935.
• Additional generators installed in 1949 and 1954.
• Installed maximum production 105MW.
• Annual production enough for 62,000 average homes.
