Thousands of tonnes of sand could be removed from popular Bay of Plenty beaches to extract the fuel soaking into the ground.

With the salvors of the Rena reporting that the ship's two remaining oil tanks are not leaking, much of the focus is on cleaning up the 350 tonnes in the sea and on beaches.

Maritime New Zealand is negotiating with local companies to dig up badly affected spots or areas where the oil is difficult to remove by hand.

The agency estimates that for every tonne of oil soaked into beaches, 10 tonnes of sand will have to be removed.


Coastal and marine systems expert Professor Chris Battershill, of Waikato University, said removal of sand was a last resort, but it had the advantage of completely extracting the toxic fuel from the beach environment.

"Depending how high the extraction rate is, all the oil can be recovered. The sand is then put into cleanfill, but you would have to remove thousands and thousands of tonnes for it to leave [a scar] on the beach."

After a Queensland oil spill in 2009, 2500 tonnes of sand was removed from beaches.