Engineering ‘complex as brain surgery’
State-owned energy company Transpower is on track to flick the switch on the major new power line running from Whakamaru, near Taupo, through the Waikato to Auckland.
“The $824 million North Island power grid upgrade is on target for commissioning in November,” Transpower Alliance project manager Ian Ditchfield said.
Only about 50 of the 426 pylons remain to be strung with power lines, work that involves helicopters flying backwards for some of the time.
The upgrade has been under way since 2009, with the physical work expected to be completed in September. Final testing will be carried out before the lines are turned on in November, with the power fed into the power grid servicing the upper North Island.
The project won an environmental award this month in the Deloitte Energy Excellence Awards.
The work on the new power line is being carried out by Transpower Alliance, a grouping of Transpower, Balfour Beatty and United Group.
“The work was always going to be a technical and environmental challenge,” Mr Ditchfield said.
The project involved more than 300 landowners, nine councils and six government agencies. More than 180,000 cubic metres of earth were moved. About 156 hectares of exotic forest and 216ha of vegetation were cleared to make way for the pylons.
‘‘Careful environmental planning, monitoring and compliance have all been part of the success of the project,’’ he said.
“More than 2460 trees and 14,893 shrubs have been planted in mitigation. The project also actively sought to reduce carbon emissions, and to minimise the impact on communities.”
Transpower worked closely with regional councils, the Historic Places Trust and iwi representatives over onsite work requirements.
“That early and ongoing consultation was extremely important throughout the project, enabling faster processing of management plans, sediment control plans, site specific consents and permits for construction activity,” Mr Ditchfield said.
During construction, existing farm tracks were used where possible, reducing land disturbance. Those that were made became assets to the landowners who will be able to use them after the project is finished.
When vegetation needed to be cleared, a “stay on the farm” approach was used so that cleared vegetation was not going to waste.
It was made into either landscape mitigation mulch for sediment barrier control, milled onsite and used for fencing, donated to local schools or stockpiled for the landowner.
Earthworks were reduced by using dura mat for temporary tracks, and a tracked Lo Drill rig that could
Careful environmental planning, monitoring and compliance have all been part of the
success of the project.
– Transpower Alliance project manager Ian Ditchfield
operate on angled slopes was used when preparing foundations.
Specially extended and crane-suspended concrete pump hoses were used to pour the foundations.
Environmentally friendly oils were also used to prevent concrete sticking to the formwork so contaminants would not discharge onto the land, he said.
The large-scale upgrade also involved some tricky electrical engineering operations, including the largest and most complex of its type in New Zealand described as being as complex as brain surgery, Mr Ditchfield said.
This large operation required a temporary power line, known as a bypass, to be built on a Morrinsville farm near the point where the new line crossed the existing power line running from the Hamilton to Coromandel line.
This was to ensure power continued to get through to Coromandel and surrounding areas while live power lines were strung on the new line.
The upgrade project was controversial when first mooted, because affected Waikato landowners did not want power pylons marching across their properties.
There were also concerns among some that the Waikato was being ‘‘used’’ to service Auckland’s power needs.
A board of inquiry was set up, and determined the project could go ahead. Transpower negotiated easement payments with each affected landowner or bought property as required.
It is understood some landowners received considerably more than $500,000 each, and some considerably less, depending on the amount of their land involved.
Transpower describes the North Island grid upgrade as ‘‘super infrastructure’’, to meet growing electricity demand for the next 100 years, providing stability of supply in the Waikato as well as Auckland.
ON TRACK: Transpower on track to flick the switch on.