Almost $10 million in costs have been shaved off the Waitaki Dam and Power Station upgrade.
Started in 2013, the project is projected to come in well under its $45million budget at $36million and be completed in about two years.
Meridian’s strategic asset manager Richard Griffiths said the savings were achieved through design choices.
He said work remained in the Hornell Gallery, a tunnel at the base of the dam which is home to the dam’s drainage system, and that was going to be complicated, and there would be minor touch-ups elsewhere.
However, the overall programme was complete and physical work on the gallery would start next year.
A lot of the equipment replaced during the upgrade had been constructed in the 1930s, 1940s and 1950s.
"One of the things that is quite important to understand is the era of this equipment. Where reasonable we’ve made some modifications to it so if you get a fault the equipment is not irremediably [damaged]."
As part of the refurbishment project in the big machine hall,where the tops of the generators sit, the fire suppression system was updated.
The station room used to be filled with carbon dioxide, but it was heavy and toxic to humans so the decision was made to install an Inergen fire protection system, a blend of gases that is released into a fire area. It has oxygen in it so it can support life, but not enough to support a fire.
"It’s a life support service."
Other work included the recommissioning of one of the turbines. Its wicket gates froze in 1998 and it was decommissioned due to the repair expense, until this project came up and the decision was made to recommission it.
The turbine was pulled up out of its shaft and refurbished from top to bottom meaning it will again be able to take water and generate electricity.
"It’s not far off being back in service."
Mr Griffiths said a lot of the upgrades concerned planning for future equipment failure and preparing for that.
An example was earthquake-proofing the roof of the machine hall. There was a fear a major seismic event would send the roof plummeting on to the generators, but work on the roof’s connection point to the downstream wall now meant the roof would move inside a joint system in the event of an earthquake.
Erosion work on the dam’s tailrace was carried out by McConnell Dowell and Smith Crane and Construction.
In 2015, McConnell Dowell won an award for its work on the dam at the Civil Contractors New Zealand Canterbury Branch Contractor of the Year Awards.
According to the company’s website, it gained the Innovation Award for the Waitaki Erosion Remediation project carried out at dam.
"It involved design, consenting and construction works for three separate parts of the dam upgrade: the tailrace right bank erosion remediation and protection works at the switchyard, the sluice pier remediation works and the left bank anchoring."
Mr Griffiths said the power station itself needed a power source and that had come in the form of two 1930s 250kW rated auxiliary machines. Those had been decommissioned and the dam now sourced its power from its Transpower connection.
The project had taken tens of thousands of hours and had no lost-time injuries, a safety record he was keen to keep intact.
He said an ecological success was that the critically endangered black-billed gulls had returned to the dam to nest.
The majority of the work has been done but a further 18 months will be needed to start on the last part of the project, the upgrade of the Hornell Gallery, projected to start midway through next year.
The work will be well within the dam’s walls, under the water level, in an area where big rigs or machines could not be placed.
Workers will join the newly drilled pipes, located in the dam-facing wall, designed to draw water out from under the dam that could, if left over time, compromise its security.
"To ensure we have confidence in its ongoing operation, we’re upgrading the drainage system in the Hornell Gallery.
"It’s giving us confidence there we don’t have to do any real significant remedial work in a seismic event."
The new network of pipes would draw the water out through a sump pump and drain it
through a pump shaft in the centre of the gallery before expelling it down the dam.
"The work we’re doing is around operational continuity," Mr Griffiths said.
