The incident happened on 13 December 2012, when the BP Exploration Operating Company Ltd was draining a surge relief line connected to the 175km-long, 91cm-wide Ninian pipeline system. After draining water from the line, a hose running between a valve on the pipeline and a manhole allowed unstabilised crude oil under high pressure to escape. The valve should have been shut off as soon as oil began to flow.
The loss of containment was unobserved for 30-40 minutes, as the worker responsible was busy with other activities. Meanwhile, according to local reports, the hose had come out of place, allowing almost four tonnes of oil to spill onto the ground. None went beyond the boundary of the terminal, the cleanup operation being assisted by the frozen conditions at the time.