Diesel spill in Coromandel Harbour

A mussel barge spilled about 500 litres of diesel when it sank in the Coromandel Harbour this morning.

Divers have been called in to seal the leak to prevent more diesel spilling from the barge, which had about 2,000 litres on board.

Environment Waikato had earlier estimated the ship's capcity to be far bigger and the amount spilt to therefore be around 4000 litres.

Its emergency management officer Adam Munro said impacts on people and the environment were likely to be minimal.

"Because the spill is unlikely to cause damage to marine wildlife -- including nearby oyster and mussel farms -- or the environment, the best response is to allow the diesel to break up naturally, but we will continue to monitor the situation," he said.

"The ocean contains bacteria that break down the molecular structure of oil into less complex substances that are not hazardous."

Environment Waikato staff will be monitoring the shoreline and breaking up any concentrated pockets of diesel which form near the beach.

Diesel is a very light form of oil, which is non-flammable and non-volatile on water. It spreads out very thinly over the surface of the water, appearing as a yellow-green sheen.

Mr Munro said conditions in the harbour are flat and calm which may prolong the amount of time it takes for the diesel to disperse.

However, 20-knot south-easterly winds forecast for later today should speed the breakdown process.

- NZPA