How this first-time innovation helped BAM turn the tide in Devon

Major works to repair, re-enforce and reconstruct a battered sea wall on the Devonshire coastline are almost complete. 

BAM is nearing construction programme completion of a larger sea wall defence and railway in Dawlish for Network Rail. 

The £80 million public scheme is in part to protect the town and rail line from extreme weather and rising sea levels – but also in response to a fierce storm in early 2014 which destroyed a portion of track running parallel with the coastline, leaving Cornwall and much of Devon without rail connections to the rest of the UK for weeks.  

It is the result of years of detailed studies, designs and joint working between marine, coastal and railway engineering experts, as part of the South West Rail Resilience Programme. 

Scope 

The first section of the new 8m-high sea wall – which is 2.5m taller than the previous one – runs 360m from Colonnade to Boat Cove and was completed in July 2020.   

Works on the 415m second section, stretching from Coastguard breakwater northeast of Dawlish station to Colonnade breakwater, began in November that same year.  

BAM constructed and installed 164 wall panels, 203 pre-cast blocks and 189 recurve units, which return waves back out to sea.    

It also built a link bridge running parallel to Colonnade viaduct that joins the two sections together, a promenade and ramp, and a new stilling basin (including 140,000 hand-laid granite blocks) where Dawlish Water runs under the viaduct and into the sea. 

Challenges  

Construction on the coastline was not without its challenges, including the discovery of an uncharted gas main which pushed the programme back by weeks.  

Then heavy rain, wind and freezing temperatures during winter caused further delays.  

And the shifting tides also had to be negotiated. 

“The physical challenges of the site have really tested the problem-solving skills of our engineers but the results are there for all to see” Alan Cox, managing director for transport at BAM, previously said.

“It’s a project that has exhibited incredible ingenuity and collaboration from everyone involved right from the outset back in February 2014.” 

Solutions 

BAM used an innovative eight-legged, self-contained walking jack-up barge, known as a “Wavewalker”, during construction to install new piling. 

It is understood to be the first time this type of barge was used to upgrade the UK rail network. 

It enabled the team to work across the high tidal ranges that particularly impact the south Devon coastline.  

Cox added: “Whether it was the use of stone-filled containers to protect the area following the initial failure in February 2014, the use of the Wavewalker to install the new piling or the development of a bespoke low-carbon structural concrete, innovation has paved the way for remarkable achievements.” 

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