Overcoming unique challenges

Ten years on since the railway in Dawlish, South Devon, was almost washed away, during a notorious storm, BAM has played a vital role in rebuilding and safeguarding this vital south west rail route.

BAM is working with Network Rail in South Devon to ensure that an iconic coastal stretch of railway is safer for trains and passengers. In 2023 BAM completed the construction of a new sea wall at Dawlish, and BAM is now working to protect a nearby section of track from falling cliff debris, as part of a £165 million rail resilience programme.

The scenic stretch of South Devon coast near the town of Dawlish attracts around half a million tourists each year. The path of the railway line that runs through the town hugs close to the coastline for several miles: described by Network Rail as a ‘vital artery’ connecting the South West to the rest of the UK.

But the constant battle with elements, especially coastal erosion, makes this one of the UK’s most complex sections of rail infrastructure to maintain. In 2014, the line had to be closed for almost two months after heavy storms wreaked havoc on the infrastructure in the area.

Network Rail’s response to this devastation was the South West Rail Resilience Programme (SWRRP). As part of this programme, BAM completed a new £80 million sea wall at Dawlish in 2023 and is now working on a new project to protect the track between Dawlish and Holcombe from falling cliff debris.

Building in resilience

Following the storm damage in 2014, BAM carried out emergency work enabling the line to be reinstated in just eight weeks. But it was clear that major work was needed to mitigate against similar devastation in the future.

In response, Network Rail developed the SWRRP: designed to ensure the route is protected and fit for purpose for the next 100 years. After several years’ detailed planning, in 2019 the contract to build the new sea wall at the heart of the programme was awarded to BAM.

Dawlish is a uniquely challenging location for construction work: with marine working and a main river right next to an operational rail track, as well as listed buildings and sites of special scientific interest (SSSIs) to contend with.

Reshaping the sea wall

The new sea wall has been carefully designed and rigorously tested in a series of simulations, subjecting many different combinations of the design elements to a variety of predicted wave conditions.

Following these tests, BAM started construction in 2019, in a two-stage process. The first section of the new wall is 360 metres long, running from Colonnade to Boat Cove. This section opened to the public in July 2020.

Work on the second, 415-metre section – which stretches from the Coastguard breakwater north east of Dawlish Station to the Colonnade breakwater – began in November 2020. The key deliverable from this is a new safer and much wider public promenade.

By late summer 2022, the main sea wall in this area was taking shape, with the installation of 164 wall panels, 203 pre-case blocks and 189 ‘recurve’ units, which dissipated the destructive power of the waves by returning them back out to sea.

The final piece of this jigsaw involves BAM engineers joining the two sections of wall with a link bridge that runs parallel to Colonnade viaduct, as well as building a new stilling basin where Dawlish Water runs under the viaduct and out into the sea.

Some 500 metres of platforms at the station have also been renewed, and BAM has created a new accessible footbridge.

The physical challenges of the unique site have truly tested the problem solving skills of BAM’s engineers. This has been compounded by other issues that emerged during construction work: not least the discovery of an uncharted gas main, which pushed the programme back by several weeks.

What’s more, the operational infrastructure has remained live throughout the works, to make sure that passenger and freight services were not disrupted.

Towards the end of the sea defences project, over the winter of 2022/23, heavy rain, wind and freezing temperatures caused widespread disruption across the country, including on the rail network. These difficult weather conditions slowed down or prevented activities such as pouring concrete and grouting paving.

However in late February 2023, the heavy machinery was finally removed from the beach, giving the public step-free access for the first time to the King’s Walk promenade and beach via the Colonnade underpass.

Practical low carbon solutions

From the start, Network Rail has been very keen to limit the project’s carbon footprint and reduce the chances of it contributing to further climate change.

So BAM has worked to ensure that the concrete used in the construction of the sea wall uses a by-product of steel manufacturing (Regen GGBS or Ground Granulated Blast-furnace Slag) to replace a high proportion of the cement.

A special pourable formulation of the concrete had to be created – in partnership with Hansen – to allow up to 200 cubic metres to be poured in a single overnight period, between tight tidal windows.

Over 40 percent of the total concrete used (28,360m3) was a low-carbon mix, resulting in over 2,000 tonnes of CO2 savings (the equivalent of over 5,000 fewer deliveries or 48.75km of concrete wagons lined up end to end).

Walking on water

BAM used a unique and innovative platform to carry out piling work for the foundations of the sea defences, enabling round-the-clock working regardless of tides. The eight-legged ‘WaveWalker’ was the only one of its kind in Europe and this project was the first time this type of jack-up barge had been used to maintain the rail network.

Using the WaveWalker allowed BAM to complete the work more cost effectively and significantly faster than traditional approaches, minimising the impact on rail passengers and local communities.

The benefits to the marine environment were also significant. BAM’s approach avoided the need to excavate large amounts of rock from the beach and meant that reefs were protected in the process of ‘walking up’ the foreshore. Not only did this significantly de-risk the programme, but it also saved around three to four months on the schedule.

Natural protection

In 2022, BAM announced its most recent contract for the SWRRP, to carry out work that will protect a particularly vulnerable one kilometre long stretch of track between Dawlish and Holcombe.

BAM has carried out extensive ground investigations and site surveys to develop a detailed design for the scheme. In some areas, they are building catch fences to stop any loose material from the cliffs actually falling onto the railway lines, while in other high-risk locations netting is being installed in partnership with BAM Ritchies to stabilise and retain the slopes.

Protecting the natural environment is key in this contract. BAM is working closely with Teignbridge District Council on the section of work that overlooks Marine Parade in Dawlish, as well as with Natural England on the areas that fall within the Site of Special Scientific Interest (SSSI) on the Dawlish cliffs.

Although some vegetation inevitably needs to be removed for access, within a few years much of the underlying infrastructure work will visually disappear under a new green carpet of native species.

Ensuring land access and gaining consents has been a key enabling process on this project, involving numerous landowners. The South West Coastal Path also runs alongside some areas of the project, and BAM recognises the importance of keeping this open as far as possible during the work, without jeopardising public safety.

Despite a few setbacks due to unseasonable weather in Spring 2023, the BAM team delivered this complex but rewarding project, which was officially opened in early July 2023.

Awards

The project scooped the ICE South West Civil Engineering Award for 2021, in the Project Over £8m Re-engineered category.

“Since the infamous storms washed away the railway in Dawlish in February 2014, we’ve been working on behalf of the government to develop and deliver long term solutions that will protect this iconic stretch of railway from storms and climate change. The new Dawlish sea wall is already doing its job and we are delighted to have worked with BAM Nuttall who have done an incredible job in very challenging conditions. It has taken skill, creativity and determination to deliver this sea wall which will protect the railway and Dawlish for many decades to come” Matt Jackson, Project Director – Enhancements (Wales and Western), Network Rail

Don’t just take our word for it…

In 2021, the Network Rail Media Centre featured the benefits of using low-carbon concrete Read the press release

The BBC website reported on how Minister for Transport Mark Harper unveiled a plaque to mark the completion of the sea wall in July 2023 Find out more

Rail Engineer explained how the innovative ‘Wavewalker’ was used to help build the sea wall Discover the article

Network Rail explains some of the complex issues involved in the latest element of the SWRRP, to strengthen the cliff faces Read about the planned works