Major maritime pollution incident

Impact 5
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risk indicator
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Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


There is a risk of major maritime pollution in UK waters, which could result from the accidental spillage of oil from tankers or leakage from pipelines. These incidents are infrequent but do occur on occasion. For example, hundreds of barrels of oil were recorded to have spilled into the Irish Sea in 2022 following a pipeline leak off the coast of Wales. The UK has plans and procedures in place to deal with pollution at sea in order to quickly respond, limit and reduce impacts on the environment, marine habitats and local coastal communities, working with local authorities, resilience forums and emergency services to communicate and plan for such eventualities.


This scenario involves the spillage of 100,000 tonnes of crude oil into UK coastal waters. The cause could be vessel collision, fire or grounding. The spillage results in up to 200km of UK coastline being contaminated with the associated environmental impacts. Depending on the type of oil and extent of the contamination, there could be impacts on land, water, animal welfare, agriculture, waste management and air quality. An extensive clear-up operation on shore may be needed as well as some long-term restrictions on local fishing in the affected area.

Key assumptions

The scenario assumes that a fully laden oil tanker leaks in UK coastal waters. The vessel would not sink or prevent access to liquified natural gas terminals or port infrastructure.


A more impactful scenario would be an oil spill near a populated area, disrupting the safe and efficient operation of a major port. This is less likely due to the compulsory use of experienced pilots within port boundaries. A small vessel could run aground and leak a small volume of fuel but containment, clean-up and vessel refloating is straightforward. A less likely, but more impactful, scenario would occur if the ship were to sink or oil ignites and lives are put in danger.

Response capability requirements

The strain on subcontractors and wildlife conservationists would be significant. There would be a need for recovery vessels to be deployed to remove the excess oil. The Maritime and Coastguard Agency (MCA) would need to work with shipowners, the Secretary of State’s Representative, salvors, and ship insurers to organise the removal of the vessel (if safe to do so). Local authorities, the Environmental Agency and environmental groups would need to assess the damage to the coastline, marine life and wildlife. Local fishery restrictions would be applied while a full investigation is undertaken, which could last at least a year.


Recovery may take several years. Satellites would be used to assess and monitor oil spread and movement to ensure that oil recovery vessels are deployed appropriately. A significant clean-up operation of up to 1,000 people would be required to return the coastline, beaches and wildlife to a natural environmental state.
The Royal Society for the Protection of Birds would need to set up a temporary bird and marine life hospital to treat as many birds and seals as possible. The MCA would be responsible for managing stand-by response vessels. An investigation by maritime accident investigation would be required. Additionally, there would be fishery restructuring required and severe economic impacts locally.