Work will start on deepening the Rangitoto Channel early next year to allow a new generation of huge container ships to visit the Port of Auckland.
The $20 million project, given the final go-ahead this week, has been delayed by seven appeals lodged against an Auckland Regional Councilrecommendation in October last year granting consent for the deepening.
All have now been settled including appeals lodged out of concern for fish stocks in the Hauraki Gulf and for the safety of large numbers of whales and dolphins in the gulf if the deepening involves blasting.
Conservation Minister Sandra Lee gave her approval to the project this week.
The project will involve dredging up to 1 million cu m of material from the seabed to deepen the 9km shipping lane by up to 1.5m. The shipping lane at present is 11m at the shallow points at the lowest of low tides and not all the channel will have to be deepened.
If blasting is needed - Ports of Auckland says it will be a last resort - it will occur in an area of Parnell grit rock covering about 100m by 200m of seabed and there will be no water spouts or flying rock because of the small explosive charges used.
While the dredging will start early next year the removal of the Parnell grit rock, a kind of relatively weak sandstone, is expected to begin this year.
Trials have shown the rock can probably be removed mechanically but should blasting be necessary, noise devices will scare fish away.
Settlement of an appeal by the environmental group Friends of the Earth concerned about the impact of blasting on whales and dolphins has led to marine mammal protection measures of a high international standard.
Material from the seabed will be mixed with cement to make mudcrete to be used as reclamation fill for the Axis Fergusson container terminal extension.
The ports company says there should be little or no silt or other dredged material appearing on beaches.
