Mass oil spill recovery – sweeping arms proove to be the best tool

Authorship

Tom Achterberg, KOSEQ, The Netherlands

Publication

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 History

In 1967, the grounding of the Torry Canyon tanker in the English Channel made the world aware of big oil pollution dangers from groundings and collisions of large tankers. At that time, oil spill response awareness had only started with collecting oil spills from incidents in harbours and estuaries placing oil booms around an oil spill. Stationary oil booms at that time were too inadequate to be used at sea.

Considerable human safety problems derived from working at the stern of a supply vessel, deploying and retrieving oil booms during severe weather conditions. Once an oil boom is finally deployed, it is very difficult for the crew to place and maintain oil skimmers, deployed from the supply vessel, into the oil contained within the oil boom. Sea conditions, wind and currents all conflict with each other, and the crew have to work constantly under very difficult and dangerous conditions on a rolling and pitching deck, which will be wet and often covered with a layer of oil.

The problems with using oil booms at sea were already envisaged during the first oil recovery operations of the grounded tanker Torry Canyon, after which Mr. Gert Kampers, Managing Director of Koseq, began fine-tuning his idea for the Rigid Sweeping Arm. Together with the Dutch Coast Guard, the Rigid Sweeping Arm was further developed and tested at sea during real oil spill recovery operations in the North Sea.

Koseq has equipped now over 50 vessels with the unique rigid sweeping arms. Trailing hopper dredgers are used because of their large hopper storage capacity, but also tankers and tugs.

During 1998, the Dutch Coast Guard launched their first purpose-built, multi-role Oil Spill Recovery Vessel (OSRV) ARCA, having an oil storage capacity of 1,000 m3. Equipped with two 15m Rigid Sweeping Arms and purpose-built sweeping arm handling cranes. The ARCA has been working on a variety of oil spill recovery operations in The Netherlands, UK, France and Spain.

In practice

On November 13th 2002, near the Spanish coast, the tanker Prestige began listing in bad weather and leaking oil. Eventually the ship broke and sank to the ocean floor, over three kilometres deep. The ship was carrying 76,972 tonnes of IFO 650 heavy fuel oil, and the accident caused one of the largest environmental disasters in Europe of the last decades.

Several ships from across Europe contributed in recovering the oil. The European Maritime Safety Agency (EMSA) compiled a list of the quantity of recovered oil per ship. The best performing vessel equipped with offshore oil booms and a big oil skimmer had been at sea for 45 days and could only collect a total of 600 m3 of oil/water emulsion. This was mainly due to heavy seas and permanent weather changes, having to deploy and recover the oil boom too often, and loosing valuable time for the recovery. The performances of the Rigid Sweeping Arm systems during the Prestige spill were remarkable. It is documented independently that the vessels equipped with rigid sweeping arms are by far the most effective.

The vessels working on the Prestige oil spill equipped with our Rigid Sweeping Arm Systems were far more effective at recovering oil recovered than those vessels using containment oil booms at sea. According to figures published by EMSA, the vessels Rijndelta recovered a total of 7,032 m3 over 24 days, the ARCA a total of 5,498 m3 over 31 days and the Neuwerk a total of 1,600 m3 over 27 days of oil/water emulsion (Source: http:// tinyurl.com/yapqtpa [page 44]).

The figures prove that the rigid sweeping arm is by far the most effective technique in recovering large quantities oil (in this case heavy fuel oil), even in bad weather conditions.

New developments

Koseq produces a smaller version of the rigid sweeping arm: the compact rigid sweeping arm. The compact version is shorter and lighter than the normal arm, and therefore perfectly suited to be used on smaller vessels.

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