The port company's resource consent application to dredge 7.2 million cu m of sand, silt, clay and rock from the channel started in Dunedin yesterday.
Port Otago planned to dredge the channel in three stages, in response to the needs of shipping companies, using its own trailer suction hopper dredge New Era and grab crane Vulcan initially. Larger equipment would be brought in as well, for major dredging.
Mr Coe told the hearing the options and alternatives for the re-use of the dredged materials had been investigated in detail.
The company considered commercial re-use possibilities such as landfill or construction material, as well as in the formation of reclamations, he said.
This was not possible as there were no commercial markets where the material would be competitive and, even if such markets existed, they would only be able to take small portions, he said.
The company was not aware of any authorised reclamations within Otago Harbour and submitters' ideas to use it to reclaim intertidal portions of the upper harbour would be a major project, requiring significant community support, Mr Coe said.
Port Otago had provided sand to the Dunedin City Council for the renourishment of St Kilda and St Clair Beaches, but again that had been only in small volumes.
"The volume of sediment available ... far exceeds the potential volumes which could realistically be used for any of these alternative uses."
The only practical and viable option was for the majority of material to the disposed of at sea, he said.
The company already had consents to dispose of material from maintenance dredging at three sites - Hayward Pt, the Spit and Shelley Beach.
The combined volume allowed to be disposed of at those sites was 450,000 cu m, well short, one-sixteenth, of the capacity that was needed.
An alternative site was selected by first avoiding areas of conservation interest, that would have effects on fishing or recreation, and by avoiding shipping routes and causing flow-on effects to other beaches.
The final site, called AO, was chosen because the potential for the disposal of material to impact on Blueskin Bay, northern coastlines and Otago Peninsula, fisheries or areas of special biological communities would be minimised, Mr Coe said.
