The 143m Netherlands' flagged Fairpartner is due at Port Chalmers about June 12-13.
The latest arrival brings Port Otago's investment in vessels to almost $36million in the past 15 years, following its purchase of the $1.4million barge Hapuka and the $7 million tug Arihi in 2015-16, preceded by the $11million tug Taiaroa in 2014 and the $8.5million tug Otago in 2003.
Takutai will replace Port Otago's clam-bucket dredge Vulcan, which has a 100-year-old hull, thought to have come from Otago's gold dredge period, and an ageing 1960s-era crane.
Port Otago chief executive Kevin Winders said Takutai was ''a state of the art'' dredge, having been built in 2012 for one specific year-long job in France, and since maintained in a ready state for sale.
''Because of its [small] size it's very flexible. It'll have three times the productivity of Vulcan and no [anchor] resetting downtime,'' Mr Winders said of the four anchors Vulcan has to deploy, then reset to move.
The $8million purchase price included delivery costs.
Negotiations are under way to sell Vulcan ''as is'', Mr Winders said.
Takutai is 35m long and weighs 712 tonnes, and comes with three 13m extendable ''spud'' legs, which enables it to ''crab'' its way along the seabed, but it is otherwise not self-propelled.
Because of the 13m leg length and 19m bucket reach, it will be able to work on all Dunedin's upper and lower harbour channels.
It will be towed into place by Port Otago's smallest tug, Arihi, and spoil will be loaded directly on to the port company's barge Hapuka.
Mr Winders expects it to have a 30-year life, given its only one year of use.
New software meant real time sea-bed mapping would be more accurate, he said.
Other than installing new software and GPS equipment, the dredge's two-person crew would undertake some training and it should be working in Dunedin's upper harbour by July, Mr Winders said.
Takutaiis one of only two of its kind in the country, the other being a larger model based in Auckland.
