About 5,000 litres of oil that spilled into Halifax harbour from a Nova Scotia Power generating station has now been contained.

The utility confirmed the amount spilled late Friday, saying it is based on an assessment from its environmental response contractor.

Nova Scotia Power, a subsidiary of Halifax-based Emera Inc., said the leak Thursday came from an exterior pipe that runs from storage tanks to the Tufts Cove generating station.

Story continues below advertisement

The utility said 95 per cent of the oil that went into the water was contained in the first boom deployed immediately after the spill.

Crews aboard a helicopter and a boat organized the cleanup, which started soon after Nova Scotia Power employees discovered the leaking pipe during a routine inspection.

Environmental response crews set up three booms on the water and were using vacuum trucks and absorbent material to remove the oil.

The 500-megawatt plant largely uses natural gas to make electricity, but it can also run on oil.

Tiffany Chase, a spokeswoman for the utility, said staff were not fuelling the plant at the time of the leak.

“So there was less pressure in the pipe at the time than if we had been streaming oil into the plant for fuel,” Chase said.

Nova Scotia Power said it has launched an investigation and the clean up continues.

Story continues below advertisement

“Nova Scotia Power and its contractor will continue to implement environmental response and monitoring protocols until all of the leaked oil has been cleaned up,” the utility said in a statement.

“All appropriate operational procedures and protocols have been activated, and relevant regulatory bodies have been notified of the incident.”

The company said the three oil-fired units at Tufts Cove were commissioned in the 1960s and 1970s, and were converted to also burn natural gas in 1999-2000.

Its two natural gas-fired combustion turbines were commissioned in 2003 and 2004.