Tests are underway by rail engineers to find out how a mystery orange coloured water is entering a railway tunnel on the Cumbrian Coast line.

The tunnel, which takes trains one kilometre under ground between Corkickle and Whitehaven, sometimes floods.

To cope with that excess water and keep trains running safely, it’s connected to Whitehaven harbour by a culvert.

For decades water has drained from the railway into the harbour without an issue.

However, since late 2022 the water in Queens Dock started to change to a rusty colour.

It's believed the water, containing iron ochre, could be from historic mine workings in the area.

News and Star: Network Rail inspection team in Whitehaven tunnelNetwork Rail inspection team in Whitehaven tunnel (Image: Network Rail)Network Rail is carrying out detailed tests to find out how and where it's getting into the tunnel, and will work together alongside the Environment Agency, Coal Authority and Whitehaven Harbour Commissioners to find a long-term solution to the problem.

Phil James, Network Rail’s North West route director said: “We know this complex investigation work is causing frustration as it’s taking a long time, so we thank harbour users, rail passengers and local people for their continued patience. 

“We’re committed to working with the Environment Agency and Coal Authority to find the source of the water impacting our railway tunnel and the harbour so we can plan next steps to find a solution together. Solving this is also important for our passengers and freight, whose journeys we hope will be made more reliable and faster once the source of the mysterious orange water is made clear.”

Footage has been released showing teams carrying out overnight inspections of the tunnel after train services stopped running at 10pm on Thursday, November 9.

For safety trains are travelling at slower speeds through the tunnel due to the ongoing issue with the flood water.

Trains can only run at 20mph instead of 40mph, meaning longer journey times for passengers and freight.

Pete Miles, Environment Agency area environment manager, said: “Analysis of water samples from Whitehaven Harbour found no evidence of sewage pollution. The results did show some increased metals in the water and we are working with Network Rail who are actively investigating this further to determine the potential source.

“People can report environmental concerns to the Environment Agency on 0800 807060.”

READ MORE: Dog owner wins case against police over wrongly labelled banned breed

Testing will be ongoing for several weeks and the results will be shared with all partner agencies as soon as possible.

The hope is the findings can inform next steps and reveal the scale of what can be done to either mitigate, reduce or in the best case scenario stop the water from entering the railway tunnel entirely.

Passengers are advised to check www.nationalrail.co.uk to see how journeys on the Cumbrian Coast line are being impacted.