Valero’s major pipeline between its Pembroke refinery and its terminals at Kingsbury, Warwickshire, and in Manchester, is operational again, after repairs that have taken a month to complete.

The breach was discovered early last month and repairing it involved closure of the main A48 near Nantycaws, Carmarthenshire, in both directions for the weekend of October 14-17 and the continued closure eastbound from that time.

In a statement Valero said: “Following the breach of Mainline Pipeline on 4th October, the A48 near Nantycaws, Carmarthenshire, has now fully reopened ahead of schedule.”

In a letter to members of the Welsh Assembly rural affairs secretary Lesley Griffiths said it was estimated that around 140,000 litres of kerosene had leaked from the pipe.

Valero said: “Two water booms remain in place on the Nant Pibwr and have now been clear of oil or any oil sheen for over two weeks. We will continue to monitor the water for the foreseeable future, and will only remove these once Natural Resources Wales is satisfied no more oil is likely to migrate into the water course. In addition, we will continue to monitor the water courses for an extended period of time. As well as the boreholes by the A48, boreholes are now being sunk further into the valley to monitor for any further oil migration.

“Valero will continue to cooperate fully with Natural Resources Wales’ investigation into the leak. We apologise to all local residents and commuters for the inconvenience this incident has caused and to reassure them that we will continue to monitor the local environment to guard against any further impact.”

Valero said it put in place alternative plans to source product so that its customers could continue to be supplied with fuel during the closure, and apart from a few short-term delivery delays, due to increased delivery distances, Texaco-branded service stations had been supplied in a timely manner throughout the incident.