A LETTER sent out to neighbours living near the Furness Line at Grange revealed the extent of the work the engineers did after the derailment. 

The letter, signed off by Helen Hughes from Network Rail, described the task at hand when a void was discovered 150 metres away from the crash site. A passenger on the train, which came off the track in the early hours of March 22, described the void as a sinkhole. 

According to the letter, the team removed the tracks and excavated down to frim ground beneath the void. The engineers then treated the embankment 'using an innovative Goepolymer injection method in 182 locations resulting in a fully stable sub-base.' 

They then had to rebuild the embankment in compacted layers, and renewed 290m of track on both lines. 

The Mail: The train being re-railed by a crane after an initial investigationThe train being re-railed by a crane after an initial investigation (Image: Stave Paton)

Mrs Hughes wrote: "As you will know the site conditions in the area have been less than ideal due to heavy flooding, leading to delays in our program, which in turn has required continued 24h working to enable Network Rail safely open the line on the agreed date."

The line re-opened on April 22, exactly a month after the train derailed. 

READ MORE: Ulverston and Grange businesses welcome back Furness Line

The letter also stated that, having been given Marine and Coastal Access (MMO) and Special Site of Scientific Interest (SSSI) consent, they cleared out and released the tidal flap at a culvert to reduce the ground water levels in the area. 

Although the line is open, Meathop Road will remain closed until May 17 until Network Rail demobilises the site, the letter states. Only essential traffic will be permitted through the worksite until then. 

Previously, Network Rail boss Phil James said: "I’m grateful to the people of Cumbria for their patience whilst we carry out this complex investigation and recovery of the railway in Grange-over-Sands following the recent derailment of a Northern train." 

In the days after the train derailed, staff from the independent Rail Accident Investigation Branch did an initial assessment before work started on removing the train and repairing the line. The government body will compile a report examining what caused the crash and how to improve railway safety.