{"id":237582,"date":"2026-01-17T06:11:09","date_gmt":"2026-01-17T06:11:09","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/237582\/"},"modified":"2026-01-17T06:11:09","modified_gmt":"2026-01-17T06:11:09","slug":"tongariro-power-scheme-the-national-grids-underground-secret","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/237582\/","title":{"rendered":"Tongariro Power Scheme: The national grid\u2019s underground secret"},"content":{"rendered":"

Rangip\u014d is just one piece of a complex system covering 2600ha of the Central Plateau \u2013 a scheme that harnesses the power of water from in and around the Tongariro National Park.<\/p>\n

Built just over 40 years ago, the scheme employs a mix of pipes, channels, tunnels and aqueducts to feed water to Rangip\u014d, the nearby Tokaanu station, and the much smaller Mangaio station.<\/p>\n

A drive down the tunnel takes us deep within the bowels of Rangip\u014d; its now unused control centre (the station is controlled from nearby Tokaanu) looking like it\u2019s come straight out of a 1970s sci-fi movie.<\/p>\n

\"TheThe now abandoned control room for the Rangip\u014d Power Station, near T\u016brangi. The station is now controlled remotely by Genesis Energy’s Tokaanu Power Station. Photo \/ Jamie Gray<\/p>\n

There, a Rangip\u014d old-timer tells us much of the underground facility was hewn out of volcanic rock the old-fashioned way \u2013 hand tools and dynamite.<\/p>\n

The tour takes us to the \u201csurge chamber\u201d \u2013 a huge cathedral-like cavern where the water releases some of its force after running through Rangip\u014d\u2019s twin turbines.<\/p>\n

To feed Rangip\u014d, water is taken from the eastern side of Mount Ruapehu via the W\u0101hianoa Aqueduct, running through the small 1.8MW Mangaio Power Station before ending up in the man-made Lake Moawhango.<\/p>\n

From there, it travels 20km along the Moawhango Tunnel, known as the Eastern Diversion, takes in water from the Waihohunu Intake, falls down a vertical drop shaft, then travels along a horizontal section before hitting Rangip\u014d\u2019s turbines.<\/p>\n

Once through Rangip\u014d, the scheme gets another bite of the cherry with water diverted from Tongariro at the Poutu Intake, ending up at Lake Rotoaira and then the Takaanu Power Station.<\/p>\n

It\u2019s a similar but more complex story on the western side of Ruapehu.<\/p>\n

The Western Diversion takes in water from the Whanganui and Whakapapa Rivers, and the Mangatep\u014dp\u014d Stream, is channelled into man-made lakes, Te Whaiau and \u014ctamang\u0101kau, before moving on to the natural Lake Rotoaira.<\/p>\n

A tunnel through Mount Tihia takes water from Rotoaira to the 240 MW Tokaanu Power Station, the 200m drop ensuring it hits the station\u2019s four turbines with force.<\/p>\n

From there, a tail race takes water out into Lake Taup\u014d before it restarts its journey down the Waikato River, through nine more hydro stations, before hitting the sea.<\/p>\n

All New Zealand\u2019s big hydro projects have had their challenges, but the experts say Tongariro would take the cake as the most complex.<\/p>\n

\"GenesisGenesis Energy CEO Malcolm Johns. Photo \/ Genesis Energy<\/p>\n

Genesis chief executive Malcolm Johns still marvels at the ingenuity involved in a project built in the 1970s and 80s without the benefit of today\u2019s advanced technology.<\/p>\n

\u201cTo basically walk that geography with a canvas pack on your back and to conceptualise how you\u2019re going to build that scheme, and then to sit down in a room with a hundred people with slide rules to design it and then to go and build it, blows my mind,\u201d Johns says.<\/p>\n

\u201cIt\u2019s spread over thousands of hectares, and there\u2019s absolutely no way, in anybody\u2019s wildest imaginings, that anything like that could be attempted today.\u201d<\/p>\n

During construction, official Ministry of Works film trailers, complete with jaunty voiceovers, were commonplace in the nation\u2019s cinemas \u2013 featuring the tunnelling specialists brought in from Italy for the 13-year job.<\/p>\n

Royce Hargreaves was following in his father Philip\u2019s footsteps when he became part of the scheme 15 years ago.<\/p>\n

Like his father, Royce started as a roving operator \u2013 monitoring and maintaining the scheme\u2019s complex network of tunnels, pipelines, dams and stations.<\/p>\n

\u201cI can recall being on a callout with my old man going to several spots around the scheme,\u201d says Hargreaves, who is now the scheme\u2019s site manager.<\/p>\n

\u201cHe would carry me up ladders and it was amazing the number of places he took me to \u2013 he was a lot fitter and stronger back then \u2013 but it really created a true appreciation for me.<\/p>\n

\u201cIt was like a wonderland as a young kid going into these massive places.\u201d<\/p>\n

\"TheThe Rangip\u014d Dam. Photo \/ Brett Phibbs <\/p>\n

Hargreaves says engagement with Ng\u0101ti T\u016bwharetoa has been important.<\/p>\n

\u201cWe have a number of different iwi and hap\u016b around the power scheme, which is geographically quite widespread, so we cover different territories.<\/p>\n

\u201cAnd we are always working collaboratively with iwi to bring to fruition our long-term plans and strategies for one another.\u201d<\/p>\n

There were some controversial moments in terms of construction of the power scheme under the Public Works Act.<\/p>\n

\u201cBut we have definitely made a lot of headway since then.\u201d<\/p>\n

For Hargreaves, a bad day at the office would be seismic activity in the shaky region.<\/p>\n

\u201cBeing the Central Plateau, we\u2019ve had a few volcanic re-eruptions. That\u2019s always a challenge for us, not that it\u2019s a frequent event.<\/p>\n

\u201cWe are always at the mercy of Mother Nature, whether it\u2019s volcanic activity or even floods.<\/p>\n

\u201cIt\u2019s a big task for our civil teams and our mechanical engineers to sort of stay on top of a lot of this gear in our assets.\u201d<\/p>\n

\"RoyceRoyce Hargreaves, site manager at Genesis Energy’s Tongariro Power Scheme. <\/p>\n

Tokaanu also serves as nerve centre for Genesis Energy\u2019s hydro schemes in the North and South Islands and as a central hub for its other renewable assets.<\/p>\n

The station is one of just two North Island hydro stations with \u201cblack start\u201d capability to get the power grid up and running should it suffer a big outage.<\/p>\n

The actual power grid itself is a beast, Hargreaves says.<\/p>\n

If for whatever reason, the system goes down, it can require some coaxing to get back up and running.<\/p>\n

\u201cWe talk about brownouts quite a lot in the winter period when generation\u2019s quite low and demand\u2019s quite high, but that\u2019s when they\u2019re at risk of losing certain circuits and may look at load shedding to protect the national grid.<\/p>\n

\u201cIt\u2019s sort of like balancing plates.<\/p>\n

\u201cIf the plates fall down, then it takes a while to get them back up and running, but it\u2019s not that easy.\u201d<\/p>\n

\"GenesisGenesis Energy’s Tokaanu Power Scheme.<\/p>\n

Tokaanu has an ancillary generator to start one of its bigger machines and then that bigger machine can liven a line to the nearby Whakamaru substation.<\/p>\n

\u201cThen we can bring on another one and then it\u2019s just a matter of like a cascading effect,\u201d says Hargreaves.<\/p>\n

\u201cYou slowly bring it on bit by bit, more load, more generators, then still more load and more generators \u2013 it\u2019s a balancing act and thankfully we haven\u2019t actually had to experience that, but we do testing every two years.\u201d<\/p>\n

Hargreaves feels the scheme, and all its intricacy, is not fully appreciated.<\/p>\n

\u201cWhen you look at the manpower, the volume of soil that had to be moved and the tunnelling, and it\u2019s just amazing.<\/p>\n

\u201cI\u2019ve had a few conversations with some of the guys who were involved in the construction, and they have a lot of pride in it.<\/p>\n

\u201cI guess they were emotionally connected to it, but it\u2019s not talked about anymore.<\/p>\n

\u201cIt just exists, and they feel that there\u2019s no real appreciation of it, which is sad in a way.<\/p>\n

\u201cBut I love it, you know?\u201d<\/p>\n

Jamie Gray is an Auckland-based journalist, covering the financial markets, the primary sector and energy. He joined the Herald in 2011.<\/p>\n

Stay ahead with the latest market moves, corporate updates, and economic insights by subscribing to our Business newsletter<\/a> \u2013 your essential weekly round-up of all the business news you need.<\/p>\n","protected":false},"excerpt":{"rendered":"Rangip\u014d is just one piece of a complex system covering 2600ha of the Central Plateau \u2013 a scheme…\n","protected":false},"author":2,"featured_media":237583,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[33846,138,7410,140204,6098,2072,3556,111,139,69,4517,10112,102041,140205,3170,9095,13655,14625,223,8229,1961,46029,14344,140206,12414,140207,6730],"class_list":["post-237582","post","type-post","status-publish","format-standard","has-post-thumbnail","category-business","tag-along","tag-business","tag-desert","tag-grids","tag-hard","tag-holidaymakers","tag-national","tag-new-zealand","tag-newzealand","tag-nz","tag-past","tag-power","tag-pressed","tag-rangip","tag-scheme","tag-secret","tag-station","tag-summer","tag-the","tag-they","tag-this","tag-tongariro","tag-travelling","tag-turnoff","tag-underground","tag-whiz","tag-would"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/237582","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=237582"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/237582\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/237583"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=237582"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=237582"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=237582"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}