Dredging

Deepening our harbour

To welcome bigger ships to Napier Port, we’ll need to deepen an area next to the wharf for ships to turn and, in future, the shipping channel.

We’ve put together a proposed dredging programme that would see dredging carried out in stages. You can find out about the dredges that would be used here.

We engaged international experts to study the geological makeup of the seafloor and the material that would need to be dredged. This involved borehole drilling, vibracore sampling and laboratory analysis of the different types of material under the seafloor.

These investigations produced the models below, which show the geological composition of what’s underneath our harbour. If you’d like to read more, you can find the full report here.

Yellow: Fine to medium sands and soft to firm silt
Orange: Firm to stiff clay-like silt
Light green: Residual mangaheia group – very stiff to hard weathered sandstone and siltstone
Light blue: Mangaheia group = strong siltstone, limestone and siltstone

Proposed dredging programme

The dredging programme proposed in our resource consent application would see dredging carried out in stages.

Stage 1 would see the berth pocket (where the ship sits) dredged to 14.5 metres deep and the shipping channel and swing basin (the area immediately outside the inner port, where ships are turned) dredged to 12.5 metres. Stages 2 to 5 could see the shipping channel and swing basin gradually dredged over a period of years, as demand requires. For more information on the proposed programme, see our consent application here.

Dredging Programme, Stage 1

The design above shows the dredging that would take place for the swing basin and the berth pocket, with the grey scale key indicating the amount of dredging needed to get to the required depth.

Dredging Programme, Stages 2-5

The design above shows the dredging needed to take the swing basin and shipping channel down to a depth of 14.5 metres, with the grey scale key indicating the amount of dredging needed.

Studies

We’ve undertaken a range of studies to find out how we can minimise the impact of dredging on the environment around us.  

Dredge Volumes

Dredge Volumes

Dredge Plume Modelling

Dredge Plume Modelling

Post-Disposal Fate of Dredged Sediments

Post-Disposal Fate of Dredged Sediments

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