Corexit – the facts spread through the water column. At was used in accordance with New the start the concentration of droplets Zealand’s Guidelines for Dispersant just below the water surface is very Use – in deep water, around 20 high, increasing toxicity. But as the km offshore. About 3000 litres of oil dilutes through the water column, dispersant was used, compared with toxicity levels quickly drop. Naturally- the estimated 5.4 trillion cubic metres occurring bacteria also have much of water (or more than 216 million greater access to the oil so it breaks Olympic swimming pools), in the Bay down more quickly. of Plenty. How is it used? What effects does Corexit Dispersants are only one of a range of have on human health and options for dealing with an oil spill, and the environment? a number of factors are considered before using it, including: Research into Corexit products show its components break down relatively ▪ Water conditions – rough seas will quickly, and it’s unlikely to have break up an oil spill more quickly, ongoing effects on water or coastal but will also mean booms and areas. skimmers will not work. There have been no reports of any ▪ Oil trajectory – if a spill is heading ill health linked to either the oil or What is Corexit? towards an area that’s easy to dispersant. clean, it may be best to allow the Corexit 9500 and 9527 are two of the spill to reach the shore, and then A comprehensive on-going five approved oil dispersants held in clean it up. If the spill is moving environmental monitoring programme stock in New Zealand. Dispersants towards a more sensitive area, is studying the effects of the Rena approved for use must meet the such as an estuary or wildlife oil spill on coastal waters, led by Bay requirements of ‘Marine Protection habitat, the priority is to prevent as of Plenty Regional Council. Maritime Rules Part 132: Dispersants and much oil as possible reaching the NZ worked closely with Bay of Plenty Emulsifiers’. shore. Public Health authorities throughout the Rena response to ensure How does it work? ▪ Type of oil – some oil breaks up any public health concerns were quickly in the environment and addressed. If an oil spill occurs, the challenge is requires little intervention. Other to minimise the effects overall. We oils stay in the environment for Massey University tested affected wouldn’t normally put any chemical a long time if not dispersed or wildlife during the Rena response, into the sea, and dispersants are only collected. and the Regional Council’s ongoing used when the environmental risk from environmental programme is looking at an oil spill is greater than the risk from How was Corexit used effects on both the flora and fauna. the dispersant. when the Rena grounded? Oil from a spill floats on the surface How is Corexit stored in the of water and when in a slick, it’s very In the early days of the response to Bay of Plenty? toxic as its concentration is near the Rena grounding in October 2011, 100 percent oil. Adding dispersant Corexit 9500 and a small amount of Bay of Plenty Regional Council stores to a floating layer of oil breaks the Corexit 9527 were trialed on the heavy 3200 litres of Corexit 9527 for Maritime oil into small particles to reduce the fuel oil spilled. This was stopped after NZ at the Port of Tauranga, along with concentration, and speeds up the three days because the dispersant other equipment that may be used in natural process of breaking it down was not effective in the prevailing an oil spill Tier 2 response. It would with bacteria. conditions. No other chemicals were only be used in larger offshore spills if used. the conditions and oil was appropriate, When a slick is broken down by as required under the guidelines, and dispersants, the small particles no The response was managed by under delegation from Maritime NZ. longer float on the surface but are Maritime NZ and the dispersant For more information contact Maritime NZ toll-free within New Zealand: 0508 22 55 22 or email [email protected] GD134124.