'Violent' waves may bash oil balls to bits

Using waves to help mash up oil tar balls and clump smaller ones together is part of a new method of cleaning Western Bay beaches after Rena's spill.

Members of international group Oil Spill Response were testing the use of a bobcat digger and the waves' action this week after initial success with a first run on Wednesday.

Oil Spill Response's Andy Nevin said Wednesday's attempt at Papamoa beach yielded "very positive results". On Thursday, the crew had taped off a 100sq m patch east of the Papamoa Surf Lifesaving Club to continue the trials.

A bobcat was used to scoop up the top layer of contaminated sand and spread it on the tideline, where waves from an out-going tide would then crash over the pile.

"Basically the waves mash it up like a washing machine and it breaks the tar balls down," Mr Nevin said.

The broken-up tar balls are taken back out into the ocean, to eventually be further broken down by the micro-organisms in the sea, Mr Nevin said.

Other tar balls are expected to clump together in the action, becoming larger and more easily collected. These are expected to wash ashore along the high-tide mark. The method has been used around the world, but usually on pebble and shingle beaches.

"As a company, the Oil Spill Response have done it a few times in France and Spain when there have been big oil spills over there. It's a well known method for actually cleaning oil from beaches."

The four Oil Spill Response team members hail from England and Singapore - and cleaning up spills is their full-time profession.

Mr Nevin said they would be able to clean a 3km patch of Papamoa beach in as little as four days, but that was dependent on several variables including tide and weather conditions.

Ultimately it will be up to Maritime New Zealand and local authorities to decide if the simple method will be used.

It is understood previous attempts at mechanically cleaning the shore have been unsuccessful.