The ongoing clean-up of the Llangennech freight derailment and diesel spill site is the most challenging recovery operation since the Sea Empress disaster 25 years ago, according to the incident recovery manager.

Environmental contractors Adler and Allan have been working around the clock to complete the complex remediation work at the site where a freight train pulling 25 wagons each containing up to 100,000 litres of diesel derailed near Llangennech in Carmarthenshire on 26 August 2020. The derailment and the subsequent damage to the wagons resulted in a significant spillage of diesel and a major fire.

Contaminated soil from 150 metres of railway at a depth of two metres and width of 20 metres has been excavated during the 27/7 operation. The soil has been replaced with new, clean material from quarries in Carmarthenshire and Pembrokeshire that match the chemical and physical properties of that already on site. Contaminated materials have been removed by lorry and taken to a licenced waste management facility near Merthyr Tydfil.

Monitoring of the site and the wider environment is ongoing to ensure the safety and quality of shellfish harvested from the area. Latest laboratory results from the analysis of cockles and mussels for environmental contaminants, including oil, indicate levels continue to be well within regulatory limits.

Incident recovery manager Stuart Thomas, of Natural Resources Wales, has been at the heart of the recovery effort.

Stuart Thomas said: “This is the most challenging recovery operation we’ve seen since Pembrokeshire’s Sea Empress disaster 25 years ago.

“A phenomenal amount of work has been carried out at the site to safely remove the contaminated soil and reinstate the ground. Contractors have worked around the clock, and have had to overcome many challenges, including flooding of the site during recent severe weather.

“The physical works are now nearing completion with just the Coal Authority land to treat, replanting to take place and of course the reopening of the railway line.

“Monitoring of the site and surrounding area, which includes four Sites of Special Scientific Interest and a Special Area of Conservation, will continue for years to come.

“I’m very pleased to see the latest shellfish monitoring results continue to be well within regulatory limits. Local shellfish producers have been informed.”

The final part of the remediation is now taking place on Coal Authority land. This work includes the removal of the top layer of ground where contaminated fire water was pumped during the incident in an area of woodland to the north east of the incident site, as well as deeper excavation work at the incident site itself.

Jacobs, acting on behalf of Network Rail have provided design support for the new railway line with work beginning to lay a new track, signalling, power and telecommunication work commencing as planned on 4 January.Work is progressing to plan despite some recent weather related challenges.

Bill Kelly, Wales route director at Network Rail, said: “This is one of the largest scale environmental recovery operations Network Rail has ever been involved with and it’s thanks to the quick thinking of our frontline railway colleagues, and our partners at Natural Resources Wales, that an environmental disaster was averted.

“Over the last two months, around 30,000 tonnes of contaminated soil has been removed from site – a massive operation designed to protect the local environment for future generations.

“We are working closely with Transport for Wales and our freight operating partners to get services back up and running. The final stage of our work is now underway, and we’re making great progress installing brand new track and repairing damage to the signalling system.”