When Auckland's big power pylons first went up they were over green fields. Planners hadn't anticipated that 70 or so years later development would be so intense that high voltage lines would be humming over homes - to the extent that the legs of pylons have been used as retaining walls. Now Transpower is trying to anticipate future problems.
Electricity supply isn't generally something you spend a lot of time thinking about - until you flick a switch and it's not there.
But Auckland's rapid growth and the many new infrastructure projects that is bringing, literally changing the landscape, has the country's power supplier looking into the future for potential road blocks. Transpower is about to release the result of a year's work, its Auckland strategy for the next 50 years.
Auckland doesn't generate any of its own power, and that's not likely to change, but enough work has been done to secure both the supply and the network into and through the city to the top of the country. Work to make sure of that finished 10 years ago. Capacity is now well and truly more than the city needs, and power demand is not increasing along the same lines as the population - developments such as solar panels and more energy efficient appliances are helping that.
Because that 220kV cabling is now complete, work can begin removing some older 110kV lines, some of which may currently be over homes - homes that weren't there when the lines were installed. The work has to be done sequentially and over time but there are opportunities to take down old wires in south Auckland particularly, in Mt Roskill, areas around the Onehunga port and shoreline, and between Albany and Henderson. About 60 kilometres of lines can come down. Not all of them though - substations are required to connect the power to the 220kV lines and that's not always possible to do in built up areas.
Where lines can't be taken down, and new projects are planned around them, things get tricky.
Transpower's Selina Corboy says part of the strategy work has been to try and flush out everyone's secret plans. "Is there anything out there you haven't told us about?" she asks - and she's talking to the Auckland Council and its CCOs, NZTA, developers, and anyone who wants to plonk a new rail line anywhere. Overhead lines can't just be moved underground. To do them all, Transpower has estimated it would take decades, be extremely technically complex, and would cost more than $4 billion. Under the government's current funding framework it couldn't be paid for.
Once buried - and power lines can't be in shared trenches, or near water, and digging up roads to install them is deeply unpopular - there must still be sufficient overhead cabling to carry power in case of a fault. Overhead faults are easily spotted and fixed, but it can take up to 12 weeks to find and fix underground cables. It's much more expensive - often experts have to be flown from overseas. While underground cables are obviously not prone to high winds and falling trees, they are vulnerable to earthquakes, flooding, and accidental strikes from above. As well as that, they can't be built over. So planning new developments is more complex than just saying "we'll get Transpower to move the lines".
It also doesn't want to see any more situations where developers are pushing safety limits near lines, such as using pylons as roundabouts (this has happened) - and to that end it has got Auckland Council to include in its Unitary Plan a requirement that Transpower is a notified party when anyone wants to build under overhead lines.
It wants to be consulted before such planning gets too advanced, and work has to be re-done. One example is Panuku's plans to turn Onehunga into the Wynyard Quarter of the Manukau, where lines removal is likely to prove a problem. "We are in the way of everything," says Corboy.
Transpower has identified 12 major projects already on the books where power lines are in the way, or substantial changes to supply are required.
They include 18 connection improvements on State Highway 16, the City Rail Link, light rail, the eastern transport initiative, Special Housing Area developments at Drury, Wesley College and Flat Bush, and the Redoubt - Mill Rd Corridor.
Planning for a future we can't see
Another strand of the strategy is to anticipate what developments will have an impact on power demands, but that future is changing so rapidly that it's largely guesswork. The development of battery storage is likely to be a key factor. Larger, grid-connected batteries are not currently economic, but it's likely that will change. When it does, expect a huge uptake in solar panels in Auckland, with more potential to feed power back into the grid without the current connection difficulties.
"We think we know what's going to happen, but we don't know what we don't know," says Corboy. "We can hedge our bets but we still have to be future planning. We do know that we will absolutely still need the grid in Auckland. Even if every house has solar panels we would still need the grid in peak times, and in winter. We do know that battery storage is going to be amazingly better."
In the meantime, in order to keep that security of supply Transpower has some massive maintenance planned. Some of it will be tricky - and that includes changing out lines on Tip Top Corner. But it has to be done, if we want to keep the lights on.