Karāpiro disruptions: Two more years of road and power station work

Hydro Dam on Lake Karapiro - the road over it from the village will be closed for about 20 months over the next two years. Photo / Alistair Guthrie

Travellers heading east from the Waikato to the Bay of Plenty and south, or vice versa, will experience delays in the vicinity of Hydro Rd - to Karāpiro Village and Lake Karāpiro - as the next phase of the State Highway 1 Cambridge to Piarere Safety Improvements programme gets under way this month.

For Karāpiro Village residents and Lake Karāpiro users, the disruptions will be even worse – stage two of the $75 million upgrade to the Karāpiro Hydro Power Station is expected to be undertaken from July 2023 to May 2024 and then stage three over a similar timeframe until mid-2025.

During the work, Ariki St over the dam will be closed.

Cambridge to Piarere safety improvements plans.

Waka Kotahi NZ Transport Agency expects to start construction of a turnaround bay at the intersection of SH1/Hydro Rd on June 20. The expected timeframe is six to eight weeks, depending on the weather.

Karāpiro Hydro Power Station owner Mercury is replacing the three turbines in the station to increase output and extend the life of the plant. It is the first time the turbines have been replaced since the station was built in 1947.

The first turbine has been replaced.

The effective outcome of the combined works means disruption-free access to the lake and village, and the alternative route east and west will be available for just two months until mid-May 2025.

Waka Kotahi infrastructure delivery manager for Waikato Bay of Plenty, Jo Wilton, says the Hydro Rd turnaround is the first of five turnarounds that will be constructed on SH1 between Cambridge and Piarere over the coming year, along with additional median barriers.

Work area to create turnaround bay on Hydro Road.

“Once the turnaround is completed, over 3km of median barriers extending from the end of the Waikato Expressway to Hydro Rd will be installed.

“We are working with local contractors J. Swap and doing everything possible to minimise the disruption for locals and visitors.

“This work has been timed to coincide with Ariki St over the Karāpiro Dam being open until the end of July, offering Karāpiro Village residents and visitors an alternative route.”

Jo says it will be especially disruptive for Karāpiro Village residents, as while they will still be able to turn left in and out of Hydro Rd, they won’t be able to turn right.

Alternative routes from Cambridge will be signposted and Waka Kotahi is asking people to allow extra time for their journeys.

She says Waka Kotahi has a small window to complete the construction of this turnaround, otherwise it may not have been possible until next year.

“Weather working in our favour, we expect most of the work at the SH1 Hydro Rd intersection to be completed by the time the dam access is closed.”

The construction crew will be on site from Monday, so the recommended alternative routes are:

Cambridge to Karāpiro Village: Light vehicles take Maungatautari Rd and Ariki St (add 6-10 minutes to your journey).

Karāpiro Village to Piarere: All vehicles heading south to Piarere from Hydro Rd will need to turn left out of Hydro Rd to Cambridge, turn around at the Shakespeare St roundabout then continue south (add 10-15 minutes to your journey).

Alternate routes during work on the turnaround bay.

There will be several nights of works under Stop/Go traffic management while the site is established, and again in late July, and while the effect on SH1 traffic is expected to be minimal, temporary speed limits will be in place.

“We apologise for the inconvenience this may cause to residents and people travelling between Cambridge and Piarere and thank everyone for their patience while we work to make SH1 safer,” says Jo.

The right turn from Hydro Rd will be reinstated after the turnaround is complete, but only until the next turnaround is built north of Hickey Rd later in the year, then the right turn out of Hydro Rd onto SH1 will again be closed.

Jo says turnarounds are a key feature of the safety improvements under way on this stretch of highway as they offer a much safer right-turning option for getting off and onto the highway.

Mercury also acknowledges the disruption its upgrade will cause but says the outcome will be positive for the community.

The company has nine dams on the Waikato hydro system, aged 60 to 97 years, and is spending about $350m rejuvenating them over the next 15 years.

Construction of Karāpiro Hydro Power Station was completed in 1947 and it was commissioned in 1948.

Mercury's Karapiro Hydro Power Station. Photo / Alistair Gutherie

The upgrades will extend its life by 50 years and make the power station more efficient. When complete the station will generate an additional 16.5MW, taking output from 96MW to 112.5MW. Average annual energy production will increase by 32GWh to 537GWh.

This is an extra 17 per cent renewable power, enough for about 19,000 homes.

As well as owning the dam, Mercury also owns the road that crosses it and allows it to be used by the public.

Under the rules of the easement with Waipā District Council, Mercury is allowed to restrict public access when needed for maintenance.

Mercury is exploring the possibility of access for pedestrians and cyclists when the road is closed but says ultimately the safety of everyone is the primary concern.