ABSTRACT
Large amounts of oil exists in old shipwrecks worldwide, both as cargo and bunker. This oil will eventually enter the marine environment as the ship hulls deteriorate or as other types of activities affect the wrecks. Oil being a complex mixture of hazardous substances will when released into the marine environment be a source of both lethal and sub-lethal effects to organisms. Costs of an oil spill in the marine environment, including clean-up actions, socioeconomic and environmental costs is often substantial. Sweden has a ten year nationally funded program where oil removal operations on shipwrecks are performed. From a list of 300 potentially polluting shipwrecks, 31 wrecks have initially been selected for oil removal operations. In a first stage extensive gathering of information was performed regarding each wreck, both archive data and in-situ data at the wreck site. Secondly, a risk analysis was carried out. Based on the probability of oil leakage, amount of oil in the wreck and sensitivity of recipients, a prioritization for oil removal operations was made of the 31 wrecks. Based on the prioritization, time of the year and cost of an operation wrecks are finally selected for oil removal operation. So far, since 2017, five operations have been performed.
During 2019 and 2020, two successful oil removal operations were carried out. The ship Lindesnäs wrecked 1957 in a snow storm close to the lighthouse Norra Kränkan on the Swedish east coast with a cargo of kerosene and diesel as bunker fuel. The operation from mobilization to demobilization lasted for 22 days, and 299 m3 of oil and a large ghost net was removed from the wreck. Secondly, Finnbirch, which wrecked in 2006 east of the island of Öland and started to leak oil during the end of 2018, was salvaged in a two-part operation. In 2019, 60 m3 of diesel fuel and lubricant oil were salvaged, during a fourteen-day operation. In 2020, 114 m3 of heavy fuel oil (HFO) was salvaged from the wreck during a fifteen-day operation. The costs per ton of removed oil were far less than cost for oil clean-up operations in Swedish waters. In conclusion, using a risk-based approach for prioritization of potentially polluting shipwrecks and the subsequent proactive removal of oil from shipwrecks is a cost-effective approach to alleviate the problem.
ON ORGANIZING FIELD OBSERVATIONS OF STRAY CURRENT FIELDS ON SEA VESSELS
