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Plans have been revealed for two power stations on the Kaipara Harbour.
One will harness the swift current at the harbour entrance and the other will burn gas piped from Taranaki.
The Northland Regional Council will this week publicly notify an application from Crest Energy Kaipara for resource consents to use part of the harbour mouth to generate electricity using submerged marine turbines.
Crest Energy plans to start 200 turbines which it says will supply 200 megawatts - enough electricity for 250,000 homes.
Northland coastal consents team leader Allan Richards said the application would be heard next year by a joint commission of the Northland and Auckland regional councils and the Rodney District Council.
The councils had sought further information from the company about the effect of the project on navigation, fishing and dolphins.
Crest director Anthony Hopkins said the project was a "world first and very challenging".
Only a handful of companies in the world were building turbines to harness tidal power, which worked for 16 hours a day, in all seasons.
The company needed consents for the turbines in water 30m deep and for laying two 30km undersea cables to connect with the national grid.
The other power station proposal is from Genesis Energy, which wants a change to the Rodney District Plan to create a spot zone for a rural gas-turbine station at Kaukapakapa, 8km from Helensville.
Rodney District Council is examining a draft proposal and could publicly notify the bid before Christmas.
Independent commissioners will hear the application from the company, which also needs air and water consents from the Auckland Regional Council.
Genesis Energy spokesman Richard Gordon said the company hoped to be generating 240 megawatts by the summer of 2008-09.
Building a second stage to boost production to 360MW depended on increasing the gas pipeline's capacity.
But Kaipara Forest and Bird convener Suzi Phillips said there were concerns about the station using a non-renewable resource and emitting greenhouse gases.
The tidal power proposal was preferred as it was a sustainable option, but there were concerns about the effect turbines would have on silting and marine life.
Kaukapakapa residents' action group spokesman Judi Candy said the Genesis Energy station was on the State Highway 16 scenic route beside the harbour and its CO2 emissions would be spread all over the township.
Residents had petitioned the district council about the site being the wrong choice.
