Where the wind blows
Where else but Wellington as a site for the world’s most efficient wind farm? HUGH DE LACY checks out Meridian’s West Wind project.
It’s not just legend, nor even parochialism: Wellington is the best place in the country to build a wind farm because of the funnelling effect created by the norwesterly and southerly winds barrelling through Cook Strait from the Southern Ocean.
Accordingly, state-owned Meridian Energy, which prides itself on being a 100 percent renewables electricity generator, chose the Makara Hills west of the capital for the third and largest of its major wind farms. Called West Wind, it will produce 140MW when it comes on-stream at the end of next year, and follows on the completion of Meridian’s 90MW Te Apiti windfarm in the Manawatu in 2004 and 58MW White Hill in Southland last year.
West Wind, on which the Higgins Group began construction as principal contractor last November following a tortuous resource consent process, will comprise 62 turbines spread across a precipitous 55 square kilometre site that will see the highest turbine at an altitude of 432 metres. The site requires not only 1.5 million cubic metres of earthmoving and the construction of 45 kilometres of seven metre wide internal access roads, but is so bedevilled by access problems through Wellington’s narrow streets that a special temporary wharf will have to be built to get the turbines onto the site.
The project will generate electricity 90 percent of the time. It will be at full capacity for 47 percent of the time – more than double the international average – in wind speeds ranging from 15 to 90 kilometres per hour. In extreme conditions the turbines will shut down to prevent damage, and their output will be enough to power the equivalent of 70,000 homes, or most of Wellington.
When Meridian first announced the project in 2005, it was met with a storm of resistance from the scattered residents of the Makara Valley, who feared the sight and sound of the turbines would ruin their urban lifestyles. In its original form the project envisaged an output of 210MW from seventy 125 metre high turbines, which the objectors cited as being too many, too close and too big for the community.
The Environment Court was inundated with over 800 submissions, the majority of them opposed to the project. Its otherwise favourable decision, which comprised nearly 280 separate consents and 350 conditions, cut the number of turbines to 66 and limited their height to 111 metres. Meridian itself subsequently reduced the final number of turbines to 62 because of turbulence problems at four of the remaining sites. The alterations reduced the cost of the project by $80 million to $430 million.
Even so it was touch-and-go whether the project would be built at all. In announcing the decision to go ahead in August last year, Meridian chief executive Keith Turner said it had been saved only by the high value of the New Zealand dollar: “We have been incredibly lucky: the exchange rate peaked about the time the board gave me the [final] decision,” Turner said.
Had the dollar been any lower, the cost of buying the turbines from manufacturer Siemans Wind Power, and shipping them out from Denmark, might have canned the project.
But if West Wind at first struggled to get off the ground, it has taken flight since. The lower half of the North Island enjoyed one of the best summer construction seasons in years in 2007-08, allowing no less than 1.2 million cubic metres of dirt to be shifted in 16 weeks. By mid-May virtually all the bulk earthworks had been completed, the paving of the roads was well under way, and 18 of the concrete turbine foundations had been poured.
The construction of West Wind is in the hands of Higgins’ projects division under manager David Rubery, with Sean Dowling as senior site project manager . The list of subcontractors includes Higgins Contractors of Wellington for pavement construction, Higgins Contractors of Hawke’s Bay for stabilisation, Higgins Aggregate and Higgins Concrete for material supply, as well as Hayes Earthmoving of Wanganui and its new owner, New Plymouth-based Hurlstone Contractors, along with Waikanae-based Goodmans Contracting, Burgess and Crowley from Taranaki, and Okau Contracting from Urenui in Northern Taranaki.
Morris and Bailey from Dannevirke has the subcontract for the turbine foundations, while Palmerston North’s Blacklie Contractors is doing the specialist cabling and trenching work, and
Daniel Smith Industries of Rangiora supplies the tracked crane for assembling the turbines.
“They’re an exclusive group of site contractors who have worked with Higgins Projects on our two previous windfarm projects, Meridian’s Te Apiti and Trustpower’s Tararua T3,” Ruberry told Contractor. Higgins’ contracts overall are worth over $50 million, and the on-site staff of up to 250 is chewing through Meridian’s investment capital at the rate of $1 million to $1.5 million a week.
Higgins’ planning for the project was dominated from the start by the need to get aggregate and cement onto the site without clogging up the narrow winding roads that lead from Wellington through the suburb of Karori to Makara. The resource consent precluded the use of anything bigger than an HCV1 vehicle for most of the bulk materials, which ruled out conventional cement trucks. Instead cement for the 25,000 cubic metres of turbine foundations is carted to an on-site concrete batching plant aboard a specialist single-unit pod, and the aggregate in eight-wheeler trucks with no trailers.
To supply the metal for the internal roading, Higgins has two crushers working on site at Oteranga Bay where both the Cook Strait high-voltage electricity and Telecom fibre-optic cables come ashore from the South Island. The crushers also supply the bedding sand with its thermal and non-conductivity properties that protect the 60 kilometres of underground cabling.
Oteranga Bay is also the site of the temporary wharf that will be installed to bring the turbine components on-site. Planning for this and the quarry was constrained by the existence of Maori burial sites and Transpower’s HVDC cables.
International heavy-cargo handler Deugro will ship the turbine components to the deep-water Shakespeare Bay near Picton, to be loaded onto barges for the final trip across Cook Strait to Oteranga Bay, from where they will be distributed round the site by specialist heavy-haulage equipment operated by Tranzcarr.
The wharf is due for completion by spring, with assembly of the towers due to begin in February next year. The 15 and 16 metre diameter tower foundations are set in holes wide enough for a small roller to apply compaction round the outside. The foundations are up to 1.8 metres deep and sit on a 75mm blinding layer of concrete that provides the steel-fixers with a perfectly flat surface on which to work.
Each foundation requires 330 and 375 cubic metres of concrete applied in a single continuous pour over about six hours. Once set the concrete is covered in compacted earth with only the hold-down bolts for the towers visible above the surface.
Adjacent to each foundation a flat 40 by 20 metre pad has to be constructed to accommodate the 160 tonnes of pressure applied by Daniel Smith Industries’ 400 tonne capacity crane used in the assembly of the towers. The heaviest component is the 87 tonne nacelle atop the 70 metre tower, containing the generator, gearbox and turbine controls.
As each string of turbines is completed, it will be hooked up via the on-site sub-station, which is being built by Higgins with building subbie Rigg Zschokke of Masterton and Transfield Services. The sub-station will connect to a new transmission line being built by Higgins and United group, and thence to Transpower’s Wilton-Central Park circuit. The first power from West Wind is expected to flow in the autumn of 2009, with the project fully operational from December next year.
With so complex a project on difficult terrain, health and safety is a major priority, and an important part of Higgins’ strategy in this regard is a monthly toolbox meeting held at daybreak featuring a barbecue breakfast cooked for all on-site staff by the Meridian project team
Three barbecues are fired up to treat staff to a hearty breakfast at which the monthly environmental and safety awards are presented by Higgins. There is a fulltime health and safety officer on the site, but everyone is regarded as equally responsible and is encouraged to report any safety breaches, including speeding. A prerequisite of site access is a safety induction course that has catered to 900 personnel.
There are up to 25 20-30 tonne dump trucks and a couple of Caterpillar 740 tracked ejectors working on the West Wind project at any one time. Leading the assault on the fractured Makara earth is Goodmans’ D10 bulldozer, backed up by numerous D8s and eight D6s, a range of excavators up to 40 tonnes, and as many as 16 road-trucks distribute aggregate round the site.
“It’s the biggest bit of kit on any project in New Zealand at the moment,” David Rubery reckons, but for all the battles over getting resource consents, the residents of Makara would hardly know it’s even under way.
Contractor Vol.32 No.5 June 2008