Excavation work is set to begin in August on the multimillion-dollar Waimea dam project in the Lee Valley, about 36km south-east of Nelson.
The geology at the site has been identified as one of the major risks for the $104.4 million project and the excavation is expected to give a better understanding of that risk. Under the design, rock from the site will be used to create the dam and bedrock is also needed.
Waimea Water Ltd is responsible for managing the construction, operation and maintenance of the dam. A joint-venture between Tasman District Council and Waimea Irrigators Ltd, Waimea Water has a board of seven directors, headed by chairwoman Karen Jordan, who has more than 20 years’ experience in the UK energy sector.
Jordan was on site this week along with other members of the board and staff, together with representatives from the council, Waimea Irrigators and the contractor – a consortium of Fulton Hogan and Taylors Contracting. They were joined by Nelson MP Dr Nick Smith to see the progress to date.
Waimea Water Ltd board chairwoman Karen Jordan says there are some risks with the project but “every single best practice project device and discipline has been deployed”.
“We still have big risks,” Jordan said. “Until we start opening up the ground and looking at the geotech, we don’t know what we’re going to be in [for]. We can only guess, based on all the assessments that have been done to date.”
However, while there was uncertainty, “every single best practice project device and discipline has been deployed here”.
“All of the people here are professionals with lots of experience,” Jordan said. “So we’ve done everything we can to give us the best chance of success.”
Smith, whose doctoral thesis related to the Clyde dam, also acknowledged the risk.
“Anything that is involving earthworks and geotechnical has some element of uncertainty,” he said. “No matter how many drill holes you put in, the nature of the broken-up greywacke country that we have in a region such as this, there will be some uncertainty.”
Nelson MP Dr Nick Smith says there is going to be huge national and international interest in the project.
However, he had a “high level of confidence that those uncertainties have been well managed”.
Despite the topic of his thesis, Smith said he could offer little advice to the builders of the Waimea dam.
“My PhD thesis was so nerdy and so narrow, it’s of little practical significance for a project such as this,” he said. “It was very much around the behaviour of landslides that were quite unique to the very fine schist materials that surrounded the Clyde dam and are not of relevance to the construction of this project.”
An impression of how the dam is expected to look in the Lee Valley. The spillway is on the right.
A long-time supporter of the dam, Smith said it was “tremendously exciting” to see the project now under construction.
“This is the largest dam that has been built in New Zealand for more than 20 years,” he said. “There is going to be a huge amount of both national and international interest as this … goes from being on a plan to being a completed project.”
Smith said in the political context, he had felt a “shift in mood” around the project since the region experienced a drought over summer.
“The thing that began the conversation of the Waimea Community Dam was the drought of 2001 and the most severe drought was at the beginning of this year … and I felt a real ground shift of people saying to me: ‘Oh, we get it, why we require it’,” Smith said.
Tasman district mayor Richard Kempthorne said it was tremendous that “probably the most important project we’re almost ever likely to see in Tasman is under way”.
Kempthorne, who is not standing for re-election in the 2019 local body elections, was pleased to see the start of construction during his 12-year tenure.
“It was a gruelling process with just a huge amount of work and … each step we had to get across that line before we could go on to the next,” he said. “So to have got the 30th of November decision [by the council] to proceed and then to now see the construction starting, it’s profoundly satisfying.”
The key drivers now for the project were getting it built on time and to budget.
“That’s obviously got a long way to go yet, we’re just at the start, but … everything I’m hearing is that we’re on track,” Kempthorne said.
Jordan said Waimea Water’s obligation to its shareholders and the community was “to do our very best to deliver on our promises and so that’s about delivering on time [and] delivering to cost”.
“We’ve got challenges,” she said. “The drought has had a big impact … but there’s been lots of thought as to how we’re going to recover that and – as you can see here – we’re making great progress. At this point in time, we are reporting on time.”
Waimea Water chief executive Mike Scott said it would be a “world-class dam and asset for the region”.
“The Waimea dam has been designed to the highest standards under New Zealand and international guidelines, and the design was completed and then reviewed by a number of professional specialist dam engineers,” Scott said. “The dam is designed to have no significant damage in a one-in-150-year earthquake and to hold its contents and not drain uncontrollably in a one-in-10,000-year earthquake.”