The Marsden Point oil refinery has won approval to dredge and deepen Whangārei Harbour.
Refining New Zealand applied earlier this year for resource consent to realign the harbour entrance to accommodate larger, new generation oil tankers.
The big Suezmax tankers already visit the refinery but can only do so when they are 90 percent full because of the current channel depth.
The application attracted fifty submissions, with nearly 60 percent opposing it, largely because of concerns about an increased risk of spills.
Supporters argued that fewer ship visits would actually mean a lower risk of oil spills.
Independent commissioners for the Northland Regional Council have granted the company a raft of consents - but with more than 130 conditions.
New Zealand Refining said it was still evaluating the effect of these conditions on the dredging plan and would comment once it had done so.