Lyttelton Port wants to deepen and widen the Lyttelton Harbour channel, costing between $80 and $120 million.

To encourage larger container ships, it wants to increase the shipping channel by five to six meters, and widen it by about 20 meters.

Lyttelton Port company believes there won't be any environmental impact.

The port has already spent around $3 million engaging scientists to investigate the environmental effects the dredging could have.

Chief executive Peter Davie said studies commissioned so far indicate it's unlikely to have any effect on dolphins, their food source or the ecology of the harbour.

He said sediment will be dumped at a large site around 5 kms offshore from Godley Head..

It's now putting the future proposal out to public consultation, with a drop in session this Saturday.