Devon and Somerset Fire and Rescue Service is pumping thousands of litres of sea water into ground above the railway line near Dawlish in a bid to initiate a controlled erosion at the site.
The water is being pumped 50m from sea level up to the top of the cliff in a bid to saturate the ground and erode 350,000t of unstable ground above the rail line.
Network Rail has said that the work has been planned since the storm on 14 February when some settlement of the ground above the railway line was first identified.
According to Network Rail, the saturation of the ground will result in erosion of the unstable ground, rather than a sudden collapse of the ground. The aim of the work is to prevent a catastrophic collapse and minimise the risk of further closures to the rail line after the sea wall repairs have been completed.
Devon and Somerset Fire and Rescue Service has said that it expects to be on site for up to seven days but Network Rail has said that it still expects to reopen the line on 4 April.