January 22, 2007

devon oil spill

The Science Media Centre asked scientists and engineers to comment on the consequences of the leakage of oil and other chemicals from the ship MSC Napoli which was beached off the Devon coast.

Dr Alistair Greig, Senior Lecturer, Department of Mechanical Engineering, UCL, said:

“Without detailed inspection it is difficult to say if the previous grounding of the ship affected her structural integrity. Whenever a ship undergoes repair the work is overseen by surveyors from a classification society to ensure that the work is done correctly and the machinery and structure of the ship meets the rules of the classification society. This almost definitely would have been the case for the repair of MSC Napoli after her original grounding. Obtaining insurance for a ship that did not meet class would be almost impossible.

“The containers washed overboard will pose a danger to shipping (especially yachts and high speed ferries) for sometime to come as many float with only a few centimetres above the surface hence making them very difficult to see or detect by radar.

“If there was any doubt about the ability of the MSC Napoli to survive the journey around Portland Bill beaching was the correct decision. It reduces the chance of the ship sinking and minimises the length of coast line in danger. Any oil spill will be localised and can be contained. Generally the further out to sea the oil spill the great the length of coast line it will affect.”

Dr Simon Boxall, Associate Lecturer, University of Southampton, said:

“The MCA have carried out the most sensible procedure in dealing with the Napoli by beaching her before she broke up completely in open water. She can now be dealt with quickly and safely.

“The amounts of oil spilt so far are very small and the environmental impact very limited. Of more concern are the containers and their contents.”

Simon Rickaby, FIMarEST and Past President IMarEST, Chair of the IMarEST pollution and salvage special interest group, said:

“Controlled beaching is preferable to having an uncontrolled sinking. Recovery of cargo and substances from the surface is far easier than from hundreds or thousands of meters down. Beaching is a recognized salvage method and it is often preferable to beach a ship on a softer sandy base than risking it sinking onto rocks and causing further damage. The salvage team’s priority will be to recover the heavy fuel oil as this is a persistent oil which is damaging to the environment but can easily be recovered.

“Every container on this ship will have a unique number. Any container with cargo that is deemed hazardous will have its container number listed on the ships dangerous goods manifesto. This will also describe what class of dangerous material the container holds and its exact location on the ship. The salvage team will therefore know the type of hazard each container poses and exactly where containers are on the ship. Those no longer on the ship can easily be tracked down. Containers are very resilient. They have immense strength and tend to float to shore. Those that do sink can be found easily with sonar. “

Dr John Zhou, lecturer in environmental science, University of Sussex , said:

“Such large quantities of oil could cause hazard to marine organisms, as well as sea birds. When birds are covered with oil, they tend to lose their buoyancy and thermal insulation, and may eventually unable to fly and die as a result.

“Fish and other marine organisms may also accumulate oil and can be banned for catch for some time. Their eggs are perhaps more sensitive to oil residues.
Depending on the type of oil on board, they may stay in the environment for a long time.

“On battery acids, sulphuric acid is a strong acid, and can dissociate immediately, therefore causing pH to drop significantly in the locality. Marine organisms are used to live in waters of pH 8, and any major deviation from that will cause shock and stress to them, and some may dies as a result. More seriously, major reduction in pH will expel the CO2 in water, hence have major negative effect on photosynthesis, which in turn affect the whole food web.

“On the other chemicals on board, pesticides will definitely have major impacts on marine life, as they are supposed to kill pests, but quite often have effects on non-target organisms such as mussels and fish. The nature of the pesticides (which chemical, formulation, quantity) will determine the seriousness of the effect.”

Dr Simon Boxall, Associate Lecturer, University of Southampton, said:

“The UK has always taken the approach of bringing stricken vessels into safe haven and ideally beaching or stranding them on sandbanks where they can be safely dealt with.

“Whilst this may at first sound like it could bring a disaster closer to our shores keep in mind the problems created when the tanker Prestige was stricken by storms in November 2002. The Spanish Authorities decided to send the vessel away from shore to deep water, where she sank and ended up causing a substantial environmental disaster along wide stretchers of coast (and still today leaks oil from her deep resting place). The heavy fuel oil has the potential to cause a local problem but so far it would appear that only 200 tonnes of oil has leaked – that sounds a lot but is less than the volumes of oils washing down storm drains from road run off and from household sinks into the coastal sea over the past few weeks.

“The fuel oil is very thick and won’t flow readily in the environment – the MCA are having to heat it to make it flow in order to pump it from the Napoli’s bunkers. The short term local impact of any spilt oil will be significant but the environment will recover quickly with time and the effects will be very localised – oil is a natural product and bio degrades in the ocean fairly rapidly. Work carried out on areas of coast after similar spills show us that, with moderate amounts of clean up management, levels of oil remaining on beaches after a few months are barely detectable.

“Dealing with the heavy fuel oil is difficult in some ways as it is so thick – but that does also limit its spread making it easier to mechanically recover.

“Of more concern are reports of Pesticides and other chemicals in the containers – some of which have been lost over board. These pose a serious threat to wildlife and ourselves should they wash up on a beach. However to put this into perspective some 10,000 containers are lost over the sides of ships in storms worldwide every year. Their contents vary from plastic bath toys to dangerous chemicals and they also provide a serious hazard to navigation – often sitting just on the surface of the sea.”