Plugging the leaks

19:44, Feb 22 2013
tekapo canal repair
WORK STATIONS: From left, Jacob Birch and Derek Alston examine a map outlining the details of the Tekapo canal repair work.
tekapo canal repair
PUSHING CONCRETE: Extensive work is undertaken to reinforce the concrete pipes that will be underneath the canal.
tekapo canal repair
BIG JOB: Workers inspect one of the culverts, which will be reinforced as part of the repair work.
tekapo canal repair
UNDER THE BRIDGE: Contractors are hard at work reinforcing the State Highway 8 bridge, but at least they will get some protection from the shade.
tekapo canal repair
BRIDGE BUILDING: The State Highway 8 bridge will undergo significant seismic strengthening this summer.
tekapo canal repair
DUSTY ROAD: A site worker drives the long way to his next job.
tekapo canal repair
MOVING MATERIAL: The next stage of the lining work begins, with special projective material being laid on top of the special PVC surface.
tekapo canal repair
SWEEPING UP: A worker makes sure everything is perfectly smooth for the next stage of the canal lining.
tekapo canal repair
CONSTRUCTION TOWN: Earthmoving diggers and construction works prepare the foundations for the lining material for the Tekapo canals.
tekapo canal repair
HEAVY LIFTING: Fulton Hogan’s crane workers help assist in the lining of the canal.
tekapo canal repair
TAKING MEASUREMENTS: Surveyers inspect the specifications of the special lining material installed as part of the Tekapo canal repairs.
tekapo canal repair
PATCHED UP: More than 50 workers have been assigned to the installation of the lining material alone.
tekapo canal repair
HOLDING WATER: One of the four temporary cofferdams that support the canal during the project. They each took a day to install, and will need to be removed just as quickly for the re-filling of the canal.
tekapo canal repair
RUNNING WATER: The bulk of the repair work concerns an 8km section of the 26km canal structure, which means not all parts will be drained.
tekapo canal repair
HOLDING WATER: One of the four temporary cofferdams that support the canal during the project. They each took a day to install, and will need to be removed just as quickly for the re-filling of the canal.
tekapo canal repair
FLOWING WATER: The lower sections of the Tekapo river have been in full flow during the project.

Repairing the Tekapo canals is one of the biggest work projects of its kind in several decades. Timaru Herald reporter Matthew Littlewood and photographer Mytchall Bransgrove were invited for a site visit this week.

Imagine if you needed to plug your bathtub after it started to leak. Now multiply this by several thousand.

That's the sort of job that has to be completed during the next two summers to fix the leaking Tekapo hydro canals.

The project requires several hundred thousand tonnes of earth to be moved, more than 200 Olympic-sized swimming pools of water drained (and then refilled) from the canals, and nearly 8 kilometres of the canal to be lined with special material from Europe. This summer and the next, there will be more than 150 workers on the site. Genesis Energy, which owns the structure, estimates the repair work will cost more than $125 million.

This week we were able to get a closer look at the work. After we were issued with the hard hats, high-vis vests and a compulsory safety debrief from Genesis's engineering services manager Michael Campbell, we were led to the site. Earthmoving vehicles, cranes and other heavy machinery surround us.

"It's hard not to be a happy worker when you get to look at that view every day," Campbell says, pointing to the perfect view of Aoraki-Mt Cook.

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The 27km canal structure was built to connect the Tekapo A and B power stations in the 1970s, but in recent years, it has suffered serious wear and tear.

In 2008, state-owned generator Meridian undertook urgent repair work after it discovered major leaks caused by erosion, but even that was only a temporary measure. Then in 2011, the Government ordered rival state-owned Genesis to buy the Tekapo power stations from Meridian for $800 million.

Officially, repair work began on January 9, after the canals were drained of all their water. Temporary holding structures, known as cofferdams, will remain in place until the canals are refilled on April 22. Campbell says it took a day to install each of the cofferdams and it will take a day to remove them. Similarly, the refilling of the canal takes three days.

"That means we don't actually have much time to do this work. There's a lot to get done over the summer. Genesis can't exactly delay the re-filling, there are commercial considerations," Campbell says.

European firm Carpi-Tech won the contract for the special lining material, and has sent about 50 of its workers to the site. Many come from Hungary and Italy, and will be staying in Twizel and Tekapo. Fulton Hogan has about 150 workers tasked with earthmoving and other industrial work. Genesis bought a neighbouring farmer's land to accommodate the porta-cabins.

Campbell says about 8km of the canal needs to be lined and about two-thirds of the job will be completed this summer.

"The material is in 100m strips; it all needs to be welded together. It's surprisingly detailed. These people are the best in the world at this sort of job."

Next summer, the major work will be on repairing the section known as the Maryburn Fill.

"Logistically speaking, it's a pretty complex job - but so is most of what will be done," Campbell says.

It has also affected the neighbouring Mt Cook Alpine Salmon business, which farms on the hydro canals. More than 400,000 fish had to be "re-homed" (into rafts on the Ruataniwha or Ohau canals) or harvested after the canals were drained.

Meanwhile, most of the public access to the canal road has been blocked off. However, you can still drive over the State Highway 8 bridge.

Campbell says the project is a one-in- 50 year event. All things going to plan, this should futureproof the canals for decades to come.

The Timaru Herald