Mercury flags four-month Karāpiro Dam road closure for power station upgrade

The road across Karāpiro Dam will be closed for about four months later this year for extensive upgrades to the power station. Photo / Alistair Gutherie

The road across Mercury's Karāpiro Dam will be closed for about four months from August this year as part of the $75 million, six-year upgrade to the station.

Mercury is getting the word out early because it understands that pedestrians, cyclists and drivers are accustomed to using the dam road to cross the river and this closure may mean a change or a slightly longer drive.

"While we've closed our road for short-term maintenance before, to the best of our knowledge we've never had to close it for so long, so we wanted to give the community as much notice as possible," says Mercury head of operations Matt Kedian.

The road across the dam will be closed from August to December, and then weekends-only opening for a time from January.

Planning continues, and exact dates will be confirmed.

"The Karāpiro Dam has been part of the landscape for 75 years and we know it's well used to cross the Waikato River," says Matt.

Local iwi, the Karāpiro Lake Users Group, and other community groups and stakeholders have all been made aware of the plan.

The road closure from August is to enable one part of the planned major works on the station, replacement of the turbine headgates by Andritz Hydro.

Karāpiro Power Station output is being increased by 17 per cent. Photo / Supplied

"These act as a valve and close off the water to allow maintenance of the station generation equipment," says Matt.

"The wider program of work on the dam and power station started last year, and will be under way until 2025.

"Closing the road is necessary to keep everyone safe, and we thank road users for their patience during this time."

Construction of the Karāpiro power station commenced in 1940, during World War II, and progress was affected by war-related labour and materials shortages. It was completed in 1947 and commissioned in 1948.

The Karāpiro station comprises three identical Kaplan turbine generating units with a combined output of 96MW.

The programme of works will increase overall peak station capacity by 17 per cent, or 16.5MW, to 112.5MW (enough to power about 19,000 homes) and average energy production by 32GWh to 537GWh a year.

As well as the headgate works, major areas for attention include the turbine, generators and governor systems.

As a part of concurrent work to future-proof the station, other items are also being addressed due to either age-related issues (bypass valves and associated works) or legacy performance challenges (hydro intake gates and operating mechanisms, stoplogs).