Water is released through the control gates between Lake Taupō and the Waikato river. Photo / Milly Fullick
Water is released through the control gates between Lake Taupō and the Waikato river. Photo / Milly Fullick
Mercury will be undertaking stabilisation works to fix erosion which has appeared on either side of the Control Gates Bridge in Taupō.
The 83-year-old bridge provides the main link between northern and southern suburbs of the Taupō township but also contains six control gates to adjust the flow of the Waikato River in relation to the nine hydro-electric power stations between Taupō and Karapiro.
The two-lane bridge and gates is owned by Mercury, with the road surface owned by the Taupō District Council.
The company confirmed this week that regular maintenance checks had found that while the bridge was still safe, changes needed to be made to protect it from erosion.
The Control Gates are a critical part of the Waikato Hydro System that Mercury operates to generate about 10% of the country’s electricity. The gates were also used to respond to any risk of drought or flood in the catchment, said Mercury general manager of generation Stew Hamilton. He said the infrastructure was vital for the delivery of electricity to New Zealand.
“And as custodians of this asset we’re committed to investing in it, to ensure this 83-year-old piece of equipment continues to operate safely and efficiently for many more years.”
He said recent inspections showed a need to respond to the “ongoing erosion taking place on the riverbanks” around the Control Gates.
The remediation work would be done in two stages and preliminary work had already begun, with a drilling rig on site, on the southern side of the bridge.
The main work would happen between September and December and involved filling in an erosion spot which had formed downstream from the Control Gates, on the southern side of the river.
A drilling rig was being used to pump grout, which sets when it makes contact with the water, filling the erosion spot.
Mercury would also use the time to refurbish one of the six control gates within the structure.
The second stage of the work would happen between February and June 2025 and would involve erosion protection upstream of the Control Gates, on both sides of the river.
Stabilisation work begins near the Control Gates Bridge in Taupō. Photo / Dan Hutchinson
Specialist equipment would be used to install 12-metre-long sheet walls to protect the riverbanks from erosion.
Hamilton said Mercury was working with iwi partners, Taupō District Council and other stakeholders to ensure the community was aware of the work planned.
He said Mercury also recognised Taupō District Council’s long-term plan to replace the bridge to ease traffic congestion across the Waikato River. This work has been brought forward in the council’s Draft Long-Term Plan 2024-34, with detailed costings due to be finalised in three years and work to start in 2029-2030.
Mercury owns and operates the Control Gates structure as part of the Waikato Hydro Power System. It also owns the bridge itself, but the road surface of the bridge is owned by Taupō District Council.
“We recognise that the bridge is a major transport link, providing the main connection across the river to the town and we will work with the council, iwi and hapū partners over the coming years, to identify renewal and future plans for the control gates and the bridge.”
During Mercury’s upcoming work, there would be lane closures in place for certain jobs.
The Control Gates Bridge regulates the flow of waer from Lake Taupō to the Waikato River. Photo / Dan Hutchinson
Hamilton said they would need to temporarily close lanes at times during the work, with traffic management in place.
“This will usually be during the night, and we will keep the lane closures to a minimum. There will only be some short times when both lanes will need to be closed.”
“People will see our team working around the Control Gates and we will keep the community informed of the project’s progress over the two stages.”
He said there were no immediate safety or operational risks to the road, the bridge or the way the water flows were managed through the control gates.
People can visit Mercury’s website to keep up to date with the project.
Phase 1: Downstream erosion repairs on the southern side of the gates. Work scheduled to begin in September 2024, and finished by the end of December 2024.
Phase 2: Upstream retaining wall installation on both sides of the river. Work scheduled to begin in February 2025, and finished by the end of June 2025.
Work will take place between 7am and 5.30pm, weekdays, and Saturdays if needed.
