Hydro-electricity refurbishing under budget

The Waitaki dam, with Lake Waitaki stretching out behind it. The power station started producing...
The Waitaki dam, with Lake Waitaki stretching out behind it. The power station started producing power in 1935. Photo by Gerard O'Brien.
A $45 million project to refurbish the Waitaki Dam and powerhouse is on schedule and below budget - despite a slight delay caused by one of nature's own construction projects.

Meridian Energy began a four-year project to refurbish the dam and power station about a year ago, and Meridian Energy strategic assets manager Richard Griffiths said it had already improved the reliability of generators at the power plant.

''Key progress to date would be around [generator] units 1 and 2, we have pulled the generator rotor out and cleaned all the stators and realigned them. The interesting thing with the realignment is that they have actually managed to achieve an alignment there that was better than original, and there's quite a noticeable quietness now when it's running, so that's a bit of a coup for us.

''One of the things there, is that both those units were the first two units to be commissioned, but the quality of the original manufacturing left a little to be desired, so there were some inherent issues with getting it perfectly aligned.''

The generators would be more reliable, because of less vibration-related damage. The project would also involve a civil works programme including earthquake-remediation work so the powerhouse could cope with a 1-in-2500-year quake, and work to mitigate erosion on the power race around the sluice gates.

However, Mr Griffiths said some erosion remediation work had been delayed.

''Interestingly enough, that work got a little bit delayed. They were supposed to go in there in December and do some initial core-drilling testing of the sluice and we discovered some black-billed gulls had decided to nest there, and we discovered they were quite a rare bird. So consequently, we had to wait for them to finish their job before we could get to ours.

''Overall the project is on track and it's progressing very well. We are forecast to come well within our original budget estimation so that's all quite pleasing.''

He said work had also started on refurbishing the gantry crane, the original 1930s-built main 120-tonne machine hall crane, and upgrading the fire-protection systems.

Road safety improvements at the dam entrance and the intersection of State Highway 83 would also start ''very soon'', he said.

Meridian had started a strategy review of the Ohau hydro canal chain, including the Ohau A, B and C power stations.

''What will be a little different with those power stations is that there won't be a large-scale refurbishment like at Manapouri and Benmore to date, simply because the equipment is performing well and there are no significant efficiency improvements to be made from new rotors or new generators,'' he said.

The Ohau strategy would be mostly maintenance.

''The complicated factor for us is the interdependency between each of those stations, so if you take a unit out of Ohau A, you effect the flow of water and therefore the output from B and C.''

- andrew.ashton@odt.co.nz

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