The team said in its initial report that emergency assistance was not required for cleanup operations after the oil tanker Hebei Spirit, riding at anchor 100 kilometers (60 miles) south of Seoul, was pierced by a crane-carrying barge on December 7, releasing 10,500 metric tons of crude oil into the sea.
The oil came ashore along 300 kilometer stretch of shoreline on the country's west coast that hosts a number of fish farms and an active wild fishery. It has blackened beaches, coated birds in oily tar and cast a foul smell over a nature reserve.
China and Japan sent 100 tons of dispersant and experts under a UN emergency response plan to help South Korea mitigate the spill, which hit key fishing grounds and could damage the livelihoods of up to 27,000 aquaculture workers.
The spill is threatening to enter Cheonsu Bay, used by about 400,000 migratory birds. The bay is vital for wintering birds and large numbers of birds also use it as a stopover site during migration. If it were to become contaminated it could lead to a wildlife catastrophe, says BirdLife International.
The clean-up operation has involved some 200,000 people, mostly troops and volunteers, as well as 327 vessels, 17 airplanes and 13 helicopters.
The assessment team recommended continued monitoring and analysis to determine the impact on the environment, according to the UN Office for the Coordination of Humanitarian Affairs, OCHA.
The team included experts from OCHA, the UN Environment Programme, Canada, Denmark, France, the Netherlands, the European Commission's Environmental Directorate-General and the European Maritime Safety Agency.
The team concluded that shoreline assessment training should be carried out to assist with longer-term cleanup options and to build national response capacity to deal with oil spills.
Commending the speedy and effective reaction of the authorities, who used methods consistent with international oil pollution response practices, the team noted that follow-up activities began almost immediately after its mission was completed.
As a result of the team’s findings, Canada is deploying a team of oil spill specialists to provide shoreline clean-up assessment training to Korean personnel.
In addition, the UN Environment Programme and the European Commission will collaborate on a post-disaster needs assessment to help national authorities establish an environmental monitoring methodology.
The seven day UN-EC mission, which ended on December 22, visited the affected area by land, sea and air and established a partnership with national, provincial and local authorities involved in the cleanup.
The majority of beaches visited were cleaned, 'a result of strong coordination and the efforts of dedicated personnel and volunteers from the general public,' OCHA said.
A mission report is being finalized and will contain a number of practical recommendations to be shared with the South Korean government.
Environmentalists say it could take years for the scenic coastal region to recover from the disaster.
The crash took place after a towline connecting the barge and one of the two tugboats pulling it broke in high waves and strong winds. Some local fishermen claim the tanker was some 4.8 kilometers away from where it was supposed to be and ignored their complaints, according to Yonhap News Agency.
The spill was found to be caused by human error, including negligence on the part of all the captains involved, an interim report by the South Korean Coast Guard has found.
The Coast Guard on Thursday sought arrest warrants for four people - the captains of the two tugboats, the barge and the tanker Hebei Spirit. They were charged with negligence and violating anti-marine pollution laws.
The Coast Guard said the captains of the tugs and the barge owned by Samsung Heavy Industries are responsible for the spill after forcing the sailing in rough seas.
They knew that a warning for strong tides was issued five hours before the crash, but set sail without taking counter-measures to avoid the dangers, Coast Guard officials said.
The captains also failed to respond to two emergency radio calls from the Daesan Port authorities hours before the crash, the Coast Guard said.
Police say all parties involved deny responsibility.