The harbour entrance has become too shallow at low tide, causing problems for some vessels, and the council last year tried various methods to dredge it.
That included an excavator with a long reach arm imported specifically for the job, and using a pump mounted on a pontoon to suck up material and deposit it into trucks for disposal along the foreshore, to restore land lost to erosion.
The council's assets manager Neil Jorgensen said the pump method was only "moderately successful".
While it worked on sand, stones frequently blocked the pump, so that option was not a long term solution.
It was planned to try a different pump to see if it could do the work.
The other option being investigated was using an excavator with a long track and raised cab to reach out further into the harbour entrance.
Mr Jorgensen said another solution looked at was bringing a dredge to Oamaru, but that would have been very costly.
Not many dredges would fit into the harbour, the council would have to pay for down time when it could not work and the overall cost was expensive.
