The company has permission to unload between 7am and 11pm and trialled a 24-hour unloading operation in July, saying its wharf operations consents were coming up for renewal and it might apply to have unloading hours extended.
Unloading can be heard by some residents living on both sides of the harbour.
Noise levels were monitored throughout the first night of the trial.
Works manager Tony Gray said this week after considering noise monitoring results and the community and operational feedback, as well as consulting two community liaison groups, Ravensdown had decided night unloading "would not be something it would seek resource consent to do at this time".
"We take our community engagement seriously. An exercise like this also has practical value. Even though we won't be applying for 24-hour unloading, the trial and the community feedback has helped us in identifying other things we can do to reduce noise from our routine wharf operations."
That included the use of "white noise" reversing alarms instead of the existing "beeping" alarms on the front-end loaders, and the possibility of replacing the clip joints on the conveyor belt with vulcanised belt seams together. The clip joints tended to make a distinctive "clink" sound and as they passed over the supporting rollers beneath the conveyor belt, he said.
Comment on the trial was received from 22 residents, he said. About one-third of people commented positively while two-thirds were opposed, generally for noise and sleep disturbance reasons.
"Even though 24-hour unloading would improve efficiency and reduce costs, we have decided that the effects on the community, the costs of mitigating those effects, and operational considerations do not make it reasonable to proceed at this time," Mr Gray said.
One of the options for reducing noise was installing a continuous loader, he said, but the cost was significantly higher than the present system - tens of millions of dollars - and would require an upgrade of the wharves.
Mr Gray invited residents to an information day at the Otago University Rowing Club in Magnet St next Saturday between 10.30am and 3pm. It would be a chance for people to learn about Ravensdown's shipping operations and discuss the resource consents about to be lodged.
