Lee Haberfield, a giant of a man from the Rhondda valley in south Wales, paused for a moment from his work in the spot that has earned itself the rather sinister nickname "the hole" to reflect on how much he and his fellow railway workers have achieved over the past five weeks.

"When we arrived, it was like something out of a disaster movie. It's been a battle to say the least. But I've really enjoyed working here," he says.

Haberfield reckons there are two premier construction jobs in the world at the moment – the race to finish the football World Cup stadiums in Brazil and this one, the repairs to the train line that hugs the Devon coast at Dawlish after the devastation of the great storm of 4 and 5 February. "You'll always be able to look back at this and say you were there and you helped fix it," he says.

Haberfield is a member of the 1,000-strong "orange army" that has been working night and day to fix the hole, the 100-metre breach in a section of sea wall that supported the mainline track from London to the far south-west of Britain – and dozens of other less spectacular but nonetheless tricky breaks along a 3.7-mile stretch.

Once more unto the breach … Chris Warburton, left, and Lee Haberfield of Network Rail. Photograph: Mark Passmore/APEX

Network Rail (NR), the owner and operator of Britain's railway infrastructure, has announced that it is expecting the line to re-open on 4 April – a huge relief to residents and business people whose lives have been disrupted by the break in the line and a vital boost for the region's tourism industry before the Easter holidays.

The repair work to the line, which is costing around £15m, has been a triumph for imaginative thinking and teamwork. In the early days the first job was making sure that another Atlantic storm heading Devon's way did not cause more damage to the main breach. One early idea was to rush in a rail-mounted concrete spraying machine that had been specially built to repair a tunnel in Devon and was standing idle. It shored up the sea wall, prevent further devastation and may have helped save houses that were teetering on the edge.

Another was the decision to drop a row of shipping containers in front of the seawall, each filled with 70 tonnes of rubble, to act as a temporary breakwater as more bad weather came in.

But then came the setback of the Valentine's Day storm, which washed away another hunk of sea wall, leading to the prospect of the line remaining closed until mid-April, a disaster for businesses in Cornwall and west Devon, which are losing millions of pounds a day because they are cut off. Plymouth alone estimates it is losing up to £5m a day.

More innovative engineering came to the rescue. The Dawlish team brought dozens of concrete motorway crash barriers and interlinked them to form two "frames" in the hole. They have so far poured 5,000 tonnes of concrete into the frames to build the sea wall back up to track level.

Patrick Hallgate, NR's route managing director, said he was confident this new structure, which is connected to the bedrock, will not be going anywhere any time soon. "An unfortunate event like the one experienced at Dawlish shows how important the railway is to the region's people and its economy," he says. "I hope our efforts to restore here show how seriously we treat that responsibility."

The planned re-opening on 4 April will not be the end of the story.

Phase two will be to make the line along the Devon coast – six miles of it – more resilient. Possible schemes include reshaping the wall so it repels waves more effectively or building a break out to sea. "Those sort of schemes go well beyond railway engineering," Hallgate says. Closing the line is not an option. NR has a responsibility to maintain a line to south Devon – and the seawall protects 7,500 homes in Dawlish. There would also be an outcry if one of the most attractive stretches of rail in the world (designed by Isambard Kingdom Brunel and opened in 1846) was lost.

The third phase will be to identify a backup route. NR has come up with five options, including reopening an inland line, and will report to the government this year.

The repair work to the line at Dawlish, which is costing around £15m, has been a triumph for imaginative thinking and teamwork. Photograph: Mark Passmore/Apex

South Devon is just one spot that Network Rail has to worry about. Almost 300 sections of tracks have been flooded this year and it will cost £170m for the repairs. With extreme weather becoming more common, organisations including the Institution of Mechanical Engineers are calling for a fundamental rethink of how vulnerable infrastructure is protected. But for now at Dawlish it is all about getting the line reopened.

The project is not out of the woods. In the past few days a crack has appeared in the sandstone cliffs above the line at Teignmouth and thousands of tonnes of material may have to be removed in the coming days and weeks. NR is still confident that the work will be completed by 4 April though.

There are 300 workers on site every day – including 100 by night. Work ranges from the technical – such as fixing cables (a link between the stock exchanges in New York and London was one of those cut during the storms) – to the backbreaking. At the moment teams are "packing and jacking" – fixing ballast into the tracks – by hand fork because sections are too fragile to bear the weight of machinery.

Chris Warburton, an agent for construction contractor Amco, said he is loving the job, despite having been separated from his family in Cheshire for long periods over the past month. "It's a privilege to work on a line that was created by one of the greatest engineers of all time. Brunel's work has lasted 150 years. We just hope that ours lasts another 150."