Ports of Auckland is considering halving the amount of material it will dredge from the Rangitoto Channel to deepen the shipping lane.
The Government approved 15 months ago the company's $20 million project to deepen the channel to allow a new generation of container ships to visit theport.
The consent allowed it to dredge up to a million cu m of material from the channel to deepen the 9km shipping lane by 1.5m to 12.8m.
Ben Chrystall, the company's general manager of port infrastructure, said the new plan was to reduce the dredged channel depth to 12.5m.
This would halve the quantity of dredging and mean a smaller area of the seabed would be affected.
It also reduced the amount of material available for constructing the Fergusson Container Terminal expansion.
The company had intended to build all the 9.4ha reclamation for the terminal by mixing channel dredgings with cement, said Mr Chrystall.
Since 1999, material from maintenance dredging around the wharves had successfully been used to make a start on the terminal reclamation.
Further thought was given to this method of disposal, he said, because of difficulties the company faced with obtaining consents for disposal of maintenance dredgings at sea.
However, the plan would add 10 years to the project's life. About 5ha of the reclamation could be done over the next two years with material from the channel dredging and the next stage could be built with material from routine maintenance dredging.
Mr Chrystall said a staged reclamation was a better way of spending money because it matched construction more closely to demand for terminal space.
The shallower channel depth would mean a narrower tidal range for container vessels but the proposed depth of 12.5m was the same as the maximum draught of a fully laden ship.
The company was seeking public support for a longer reclamation period, he said, because it had to apply for a 10-year extension to the consent lapsing date.
The present reclamation resource consent lapses in mid-2006.
