An aerial view of where the knife gate will be installed to stop water flow to Tekapo A Power Station
Recently Cool Air, heat pumps, air conditioning and refrigeration specialists in Timaru, were involved in supplying and installing all the mechanical ventilation and A/C systems for the Tekapo Intake Gate Project.
Tekapo Intake Gate Project
After nearly two years of construction, the $26.5 million Tekapo Intake Gate Project was completed on time and under budget, protecting the hydro power station from alpine fault earthquake risks.
Tekapo A Power Station generates electricity from water diverted from Lake Tekapo via a 1.4-kilometre intake tunnel.
If a major earthquake hits, the intake of water between Lake Tekapo and Tekapo A needs to be shut off. Genesis was concerned that the existing intake gates (one at each end of the intake tunnel) could not shut quickly enough to resist strong water flows.
The new 50-tonne gate is designed to stop inflows from Lake Tekapo in the event of a serious emergency, such as a 1 in 10,000-year earthquake (Richter scale 7+) that could potentially send up to 680 million tonnes of water surging around the lake.
The gate can be manually triggered, but it is also designed to automatically close when its earthquake monitors hit a certain threshold, acting as a ‘dead man’s switch’.
“The gate can shut completely under its own weight and does not require any electronics or hydraulic systems,” Genesis says. “This is vital in an emergency where power may not be available, or the station’s operators are incapacitated.”
Infrastructure Overhaul
About every 17 years, the Tekapo A and B plants and associated infrastructure need to be overhauled. After the Christchurch earthquakes, Genesis re-examined seismic risks and Tekapo’s location near the Alpine Fault. The company decided the 2020 refurbishment programme had to be out of the ordinary.
The project took five years from planning to completion. It had to integrate modern gate technology into infrastructure and tunnels originally designed and built in the 1940s. This required digging 22 metres down to the original underground tunnel, and cutting a 20m hole in its roof to construct the new gate housing.
Inspection and repair of the water feed to the power station
Genesis chief operations officer Nigel Clark says it was a big challenge, especially as Genesis needed to continue operating the Tekapo Power Scheme during construction.
“As a Government-classified essential services provider, construction also had to continue throughout the Covid-19 lockdown to hit deadlines,” he says.
Genesis also used this opportunity to perform maintenance and upgrades to both Tekapo A and Tekapo B power stations.
Above ground of the earthquake gate on Tekapo A inlet
This included replacing the Tekapo B turbine runner, providing a 2.5 per cent efficiency gain and further enhancing the Tekapo Power Scheme’s long-term reliability and performance. The Tekapo Power Scheme is now back to running at its full 190MW capacity.
The final stage of the project is to beautify the former construction site with more than 400 native grasses and plants.
Cool Air Timaru Supply Mechanical Ducting and Air Conditioning
Cool Air were contracted to install Heating, Ventilation and Air Conditioning (HVAC) in the control room, on top of the hydraulic knife gate Tekapo intake gate. This installation was essential for maintaining both temperature – the control electronics need to be kept at 20 degrees – and positive pressurisation to eliminate dust.
Mechanical ventilation to positive pressurize the control room
This is not the first such installation for Cool Air, as owner, Regan Koster, designed and installed the Ophua Dam ventilation. Their previous experience, knowledge and expertise were key to securing the contract as part of the larger project.
Koster and his team faced some unique challenges. Attaching the ventilation to the shaft was extremely difficult due to the fact it is built to withstand the alpine fault! Also working out of a crane bucket with limited space and high alpine winds was a constant challenge.
The two pieces of ducting were 17 meters long each, and attaching them in the windy conditions proved difficult, and the team ended up bolting this in one piece. From there on the install went very smoothly.
Lifting in the shaft ventilation.
Another challenge was working under frozen ground as the temperatures were quite extreme.
The Cool Air part of the overall project took place over a three month period.
This stainless 600mm round ventilation shaft pumps 1100 l/s of fresh air 17 meters down the shaft with 3 outlet points. These are controlled at the top depending on the lake level, as there are stairs and ventilation duct but these will spend most of their life under water. We also added Mesh to the outlet shafts to prevent the fish getting caught up.
Key facts about the intake gate project:
- The main shaft housing the new intake gate is 22 metres deep
- The tunnel the gate sits in has a six-metre diameter and is 1.4 kilometres long
- The intake gate itself weighs almost 49 tonnes.
- Up to 130 cumecs of water flow through the tunnel – equivalent to 130 tonnes of water passing per second (or the weight of 65 cars per second)
- More than 4100 cubic metres of dirt (9000 tonnes) were removed during construction
- More than 4000 tonnes of concrete were poured
- Planning began five years ago and construction took 22 months
- Up to 35 people worked on site, with a further 25 providing support, design and management
About Cool Air
Cool Air are Heat Pumps, Air Conditioning and Refrigeration for Timaru and South Canterbury.
Located in the heart of Timaru, we serve farms, businesses, residencies and factories throughout South Canterbury.
Using up to date knowledge and our dedicated team of technicians, our aim is to always provide you with the best solutions. We’re proud to supply and install Fujitsu Heat Pumps.
Contact Cool Air if you have any questions about heat pumps, air conditioning or refrigeration.