Port Otago Dredging - proposed disposal site. ODT Graphic.
Port Otago has lodged a resource consent application with
the Otago Regional Council for its proposed "next generation"
$100 million channel deepening project.
Port Otago has spent about $1.5 million on various studies so
far and, following consultation on the initial draft released
publicly in February, says there are only minor changes to
the final, approximately 200-page application.
It appears likely the application will be publicly notified
and open for submissions.
Port Otago has maintained it has been in consultation with a
large cross-section of the community but, given the proximity
of the Aramoana salt marshes, potential effects on
recreational fishermen and sportspeople, and avian and
aquatic wildlife, it is expected there will be numerous
submissions on the project.
At the core of many concerns will be where the sediments,
suspended in the seawater, will settle, both from harbour
mouth outflows and from dumping out to sea 6.5km northeast of
Taiaroa Head.
Consultation was held over almost three years with 30 groups
including eight commercial interests, four environmental
groups, seven sport and recreational related groups and 11
local bodies or community groups.
Port Otago chief executive Geoff Plunket said effects on the
environment and coastline were expected to be "minor", noting
that the channel widening near Aramoana's salt marsh did not
impinge on its boundary.
During about 100-120 days of dredging and dumping at sea, a
"key" finding was that sand sediment would drift to the true
north rather than any other direction, the application says.
The "fine and medium silts" would be dispersed similarly
"mainly into deeper waters and canyons offshore".
"Any sediment that reaches the Otago coastline will not be
discernible to beach users," the report said.
The suspended sediment concentrations would be highest in the
main shipping channel, side channels such as at Quarantine
Island and Portobello peninsula, and inter-tidal banks
nearby. The sediment "deposition thicknesses" would not
change much during the 100-120 days of dredging.
Most of the 7.2 million cu m of sand and silts (of varying
weights) would go to the offshore dump site, with the plume
of the released sediment expected to settle 18km towards the
north and be 5km in width.
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