Refining NZ wants to deepen the channel into Whangarei Harbour so larger oil tankers can visit the refinery fully loaded.

The application by Refining NZ for a resource consent to deepen the channel has attracted more submissions opposed to the plan than those in support.

Refining NZ wants to dredge the channel so larger oil tankers can come in fully loaded, reducing shipping movements and transport costs. Those big ships already come in, but carrying less than capacity loads because the channel is not deep enough.

Smaller tankers carrying 700,000 barrels of crude oil can safely navigate through the harbour channel. However, larger tankers with a capacity of more than 1 million barrels can only come in with 120,750 barrels or only at 11.5 per cent capacity.

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Of the 50 submissions received by the Northland Regional Council, 30 were against granting of resource consent, 18 in favour while two were neutral.

NRC-appointed independent commissioners have heard from submitters in person and have asked for more information from Refinery NZ and others before making a decision.

NRC staff have recommended to the independent commissioners that the resource consent be granted with conditions.

To achieve the desired depth and alignment, five separate areas of the harbour channel will need to be dredged and an estimated 3.6 million cu m of seabed removed.

A minimum channel depth of 16.8 metres at low tide is needed for tankers to access the refinery jetty at all times.

Those opposed to the dredging plans are Maori individuals, whanau, or iwi organisations such as the Patuharakeke Te Iwi Trust Board which was deeply disappointed a cultural effects assessment was not included as part of the application.

The board is not convinced by technical reports that indicate changes to the wave climate and tidal currents would be minor.

Effects of dredging on taonga within the harbour entrance area including shellfish beds, tohora, seabirds and migrating eels and on pipi beds at Mair Bank were of concern to the board.

The Whangarei Harbour Marine Reserve Advisory Committee, Whatitiri Resource Management Unit, Bream Bay Coastal Care Trust, Fisheries Inshore New Zealand and Ngatiwai Trust Board also opposed the resource consent application.

Most of the submissions received in support were from fuel distribution and supply companies, and Northland businesses.

In his submission, Northland Chamber of Commerce chief executive Tony Collins said the impact on the environment from the dredging would be minor and acceptable.

"Northland's economic development and growth requires the right infrastructure, a skilled workforce, and the opportunity at a regional level for businesses to grow both their capability and capacity," he said.

Culham Engineering said the dredging would enhance navigation safety for all commercial vessels in the harbour and reduce movements required to transport crude oil to the refinery.