Network Rail could complete Dawlish repair early
27 February, 2014 | By Alexandra Wynne
Network Rail is to review whether it can bring forward the date for reopening the storm-damaged line at Dawlish next week.
Speaking to MPs on the transport select committee this week, Network Rail chief executive Mark Carne said there was a chance the repairs would be complete before the mid-April date given last week.
“I’m very hopeful we will be able to bring that date [mid-April] forward,” said Carne, adding that he remained cautious because high spring tides were expected next week.
“We could suffer some setbacks,” he told the committee. “We’re not out of the woods yet.”
The rail operator and owner also said it would be kicking off a study in the next fortnight to look at ways of increasing resilience in the medium term including the potential installation of a breakwater to diminish wave energy. This would either lie adjacent to the sea wall or further out to sea.
Alongside this work Carne said Network Rail would continue to collect all suggestions proposed for rerouting the vulnerable line with the aim of making “pretty firm” recommendations about routes that should be studied in more detail in June. This further work would be completed by September or October, said Carne.
Network Rail and its principal contractor Bam Nuttall are working to reinstate the line that was washed away earlier this month (see box).
Select committee chairman Louise Ellman said that Network Rail had got its assessment “very wrong” when in 2010 it said that the Dawlish flood defences were suitable.
“In 2010 Network Rail got it very wrong when it told the under-secretary of state for transport that the flood defences at Dawlish would be sustainable for the foreseeable future – it didn’t happen,” she said.
Carne replied that the approach to using historical weather data to assess the future resilience of railway infrastructure would need to be revised.
“There’ve been quite a few studies done on the Dawlish wall over the years using the wave and weather data from the Met Office and those have consistently shown that the wall was quite resilient,” he said. “Indeed, over 120 years the wall has never been breached.
“However, we recognise that with climate change and rising sea levels and increasing storm forces that [the wall] was not likely to exist forever, so the study had shown that within the next five to 10 years we would need to do some extra works to Dawlish and that was in the plan. It’s fair to say the weather conditions we saw in February were really the worst that have been experienced in living memory and beyond.
“We used historical data… to do the analysis and I think what we all have to recognise that historical analysis is not an accurate predictor of future weather patterns. Given that, we need to reconsider the flood defences and coastal defences we have across the country.”
Flood and storm damage repairs at Dawlish
Network Rail has now fully assessed the damage the winter storms in February caused to the South Coast Mainline south of Exeter. A 6km stretch of track is affected from Dawlish Warren to Teignmouth. A total of 256m of sea wall is extensively damaged, including the main 105m long breach north of Dawlish. Plus, 525m of granite parapets have failed, causing track ballast to collapse behind them, and Network Rail has 32 separate landslips and cliff failures to deal with.
The storm on 5 February washed away 80m of sea wall and ground, leaving track suspended over a gaping hole up to the houses of Riviera Terrace. After removing the track, contractor Bam Nuttall shored up the hole with sprayed concrete and formed a temporary breakwater of sea containers filled with rock, which were placed on the lower walkway at the foot of the breach.
This line of defence held firm during the second storm on 14 February, which has been described as the most severe in living memory by local residents. A further 20m of sea wall was breached extending the length of the hole. Many more individual wall, parapet and cliff failures also occurred.
The repair work has now been split into sections north and south of Kennaway Tunnel. Contractors Bam Nuttall, Amco, Sisk and Dyer & Butler are working 24 hours in two shifts to get the work finished.
At the main breach, Amco has now backfilled the hole with 5,000m3 of mass concrete to a depth of 3m against a shutter of concrete vehicle barriers. These have been tied together vertically and horizontally into the concrete with steel bars.
This week Amco was pouring a reinforced concrete strip footing and taking delivery of 120 bespoke precast concrete L units.
These will be placed on the strip footing and mass concrete to form a track bed channel with a 2m high wall to the front and a 3m high retaining wall on the landward side. Ballast will be placed in the channel to take sections of track which are being prefabricated at a nearby site inland.
Jon Masters
