Council assets group manager Neil Jorgensen said the council became aware of a substance on the water in front of the Esplanade earlier this month, but it was in such a small quantity, which evaporated quickly, that the council was unable to collect enough for a sample to determine what it was.
At low tide yesterday, more of the substance appeared and it was determined to be fuel.
A council contractor excavated a small pit at the edge of the council’s Esplanade land earlier marketed to developers for waterfront accommodation. Mr Jorgensen said he understood there was a disused fuel tank left behind from when Shell operated at the site in the 1960s that could be the source of the fuel, but it appeared to be under the neighbouring site.
The fuel appeared to seep into the harbour only at low tide and at high tide the water pressure alone appeared to hold it in, "so there must be only a very little amount in there," he said.
"The team’s on to it, and hopefully next week we’ll be able to determine whether it’s the old tank or not and get it sorted.
"Obviously we don’t want fuel leaking into the harbour, and we’re wanting to keep people informed, but it is just a small area of the harbour there — at the low tide it was less than a 5sqm area affected."
Otago Regional Council environmental monitoring and operations director Scott MacLean said council staff investigated the apparent fuel leak and it would continue to do so.
Oamaru Blue Penguin Colony research scientist Dr Philippa Agnew said she was not concerned about the harbour’s birdlife "at this stage" but she would keep in contact with the council.
