Buried line to keep Auckland's power on

Herald graphic

Transpower plans to run underground cables from Papakura to Auckland to protect the city from power cuts.

The national grid operator yesterday said its proposal - part of a revised $690 million plan to upgrade transmission lines from Waikato to Auckland - was a cost-efficient, flexible way of meeting the city's power needs.

But opponents attacked it as a minor change which would still allow Transpower to build pylons up to 70 metres high across Waikato, Counties and parts of Manukau.

Under the plan, the cables to Pakuranga and Otahuhu would run from a new terminal near Flat Bush.

Transpower would first build an underground link to the substation at Pakuranga.

Later, as power demand increased, it would run another cable to Otahuhu.

Existing pylons to Otahuhu will remain.

The plan follows power blackouts in June, when an equipment failure at the Otahuhu substation revealed the region depended on one major connection to the national grid.

A report on the blackout - which left hundreds of thousands of Aucklanders without power for as long as eight hours - recommended creating another circuit to take up the slack if the first one failed.

The underground link and plans to initially operate the new transmission line at 220kV before boosting its capacity to 400kV are the main modifications to the Waikato to Auckland link.

More than 400 pylons along a corridor through dairy industry heartland would remain, but a 110kV line built in the 1930s will be dismantled.

The pylons have drawn criticism and protests from affected landowners and residents.

Transpower will build the underground line to Otahuhu when the transmission line is lifted to the maximum 400kV capacity.

The plan must be approved by the Electricity Commission, but Transpower hopes to have draft approval by the end of the year.

It started investigating an upgrade of transmission to Auckland in 2003. But in April, the Electricity Commission rejected its plans as too expensive.

Opponents of the plans were not satisfied with yesterday's announcement.

Jon Addison, a committee member of Underground in Manukau, a group of residents affected by the plans, said the Transpower proposal was "as bad as ever".

"The impact is as horrible as the original proposal and it's a step backwards for the people of Manukau."

Mr Addison believed the power cable should run underground from Auckland through Manukau to Hunua, as the Manukau area was likely to be fully built up with housing over the next 20 years.

Transpower said that although the link would follow roads some private land could be affected.

Chief executive Ralph Craven said: "This amended proposal is more flexible in terms of when a higher voltage is needed, responds to the call for greater diversity of supply into Auckland, is less expensive than the alternatives, and makes better use of a scarce land resource."

Manukau Mayor Sir Barry Curtis said Transpower's proposed changes were a "marginal improvement on the previous plan", but were "still not acceptable". The undergrounding should be extended south to reduce the number of pylons needed.


The new plan

* A transmission line operating at 220kV, but capable of operating at 440kV, will run from Whakamaru to South Auckland.

* At South Auckland, it will go underground to Pakuranga.

* A second cable to Otahuhu will be added later.

* Capacity will be maximised on the line, postponing the need for a new line.

* Existing 110kV lines will be pulled down, but the 220kV lines will stay.

* The estimated cost is $690 million, including $91 million spent on the cable to Pakuranga.