Aramoana mole armouring project

In last year’s report, we signalled that investigations into protecting the Aramoana mole from the unrelenting Pacific Ocean had just begun. 

The 1.2km mole is integral to ensuring the Otago Harbour navigation channel maintains its current alignment and is always open to vessels. In conjunction with other groynes and seawalls, the mole directs the tidal flow in and out of the harbour, naturally cleansing sediment from the channel. 

Port Otago Civil Engineer Andy Pullar: “If the mole did not exist or was compromised, sediment drift could cause the channel and its entrance to ‘wander’ to the west. This was the case before the mole’s construction in the 1880s, when crossing the bar was fraught.” 

The past 12 months

Our Infrastructure team has been working alongside international and New Zealand experts to establish a viable seawall infrastructure solution to protect the mole. 

Infrastructure consultant Beca, which designed the Te Rauone Beach groynes, has been engaged to design the mole armouring solution with input from coastal modelling expert Oceanum. Bathymetric and terrestrial surveying of the mole and geotechnical testing of its underlying substrate are complete. 

Where are we at?

Andy says the next step is testing the design assumptions in one of the University of New South Wales Water Research Laboratory’s wave basins. “By building a scale model of the proposed design, we can test and measure the actual impact of conditions expected to occur over the life of the structure. This is proven technology that will identify any design shortcomings and, equally, any costly over-engineering.”

Concept design is well advanced and a full recommendation will be presented to the Board by June 2026.