operation was successful and 520 t of fuel oil was pumped out of the ship. It took 2 days to prepare for the operation. 3 days were spent waiting for better weather conditions and then another 2 days for the pumping operation. A Transrec oil recovery system was used for the operation.
Oil recovery at sea:
The mobilisation of government equipment and personnel started immediately after the notification of the grounding. 2 hours after notification representatives from SFT could inspect the situation from a ship, and 5 hours after notification the first booms could be deployed.
Because of the heavy weather only ocean goings booms were used. 3 separated systems were in operation with 200 m of ocean boom each. After 12 hours 4 systems were in operation. At the time of the grounding it was blowing gale force wind and the waveheigth was approximately 5-6 m. In that kind of weather booms will not be effective at all. SFT has experienced that ocean-going booms can work fairly well in waveheigths up to 3-4 m. However, the boom system must not be towed faster then 1 kt. SFT has also experienced that it some times is necessary to turn the systems around and go with the wind and sea. The recovery of the oil confined in the booms in heavy weather can be difficult. It is important to make sure that booms and skimmers in a system are designed for the same kind of weather, wind and sea. It is also important that the equipment is flexible and easy to handle and maintain and at the same time is robust. As a general rule one can say that if it is possible to confine the oil and keep it inside the boom it should also be possible to recover it. In this operation we were using a rope mop skimmer, The Foxtail, and a Transrec system. Oil concentration by towed booms can be slow and a single skimmer may be sufficient to serve several boom systems. After 4 hours of operation 10 t of oil was recovered, and after 24 hours 27 t. The rest of the oil ended up on the shoreline.
Emulsified oil:
SFT's experience with recovery of emulsified oil is mostly based on real tests in the North Sea where a relatively small amount of crude oil mixed with 40-70% of water into a stable water in oil emulsion have been released. We also have experience real operations like the “ARISAN” incident where we had to deal with heavy bunker oil mixed with 30-40% of water.
Experience show that recovery of high viscous oil makes it necessary to add water into the recovery device to reduce the friction in the discharge hose. We are often operating with hoses of 100 m and even a working pressure of 5-6 kg/c? not enough to pump the oil through.
SFT has learned that the best result is obtained by using a screw pump instead of a centrifugal pump. A screw pump will normally give you a higher pressure and at the same time mix less water into the oil. You will then have an oil with lower viscosity than if you used a centrifugal pump. By using a centrifugal pump you can also create an oil in water emulsion and as a result it takes a long time to settle the oil and emulsion breakers will not have any effect.
In addition SFT has experienced that the use of emulsion breakers are not very effective on heavy oil, but can be used on light product oil and crude oil.
The shoreline operation:
It was obvious from the first day that most of the oil would reach the shore. And a command post with an on scene commander and his staff were established in the area where it was expected that most of the oil would land. The on scene commander was from SFT but the rest of the staff was recruited from the local authorities.
The on scene commander co-ordinated the work along the beaches based on observations from helicopters, boats and local observers. Plans for the cleanup work were made where each affected area was prioritised according to the risk of damage. More than 30 km of shoreline was affected. It is important to conduct a proper shoreline survey before you start the work. Estimating the amount of stranded oil with accuracy is difficult on most types of shorelines because the distribution is seldom uniform. However, even rough estimate of oil quantity is desirable for the purpose of organising the most appropriate shoreline cleanup response and identifying the manpower requirements for the task.
The overall extent of pollution can be assessed visually by first overflying the area. A more detailed evaluation of the oil present on a short representative section of the affected shoreline can be made on foot. This
