Sea Wall extension
NR reveals ambitious plan to extend the Dawlish Sea Wall out to sea to combat future cliff falls and keep rail line open.
THE Sea Wall between Dawlish Warren and Teignmouth could be extended into the English Channel, with the railway re-aligned, if ambitious Network Rail plans are approved.
Speaking exclusively to RAIL, NR Director, Route Asset Management (Western) Mike Gallop said the biggest problem facing the wall comes from the adjacent cliffs, and that this project was the best solution to combating the problem.
By extending the sea wall, NR would create space whereby any cliff subsidence and collapse would not affect the railway.
“The options are going out onto the beach and moving the railway further away from the cliff. Sprey Point [near Teignmouth] would be the edge of the wall and we could have rock armour, too,” Gallop told RAIL.
“The project is at GRIP 3 and that ends in June 2019. The plan is to go out to tender in 2019-20 and complete the main works by 2021. It is subject to a Transport and Works Act Order and CP6 [Control Period 6, 2019-24] funding.”
Gallop said that another affected area is between Kennaway Tunnel and Dawlish, and here NR plans to “effectively build a new wall. It will have a higher beach wall and a wave return. This will be modern engineering.”
A third element to the scheme is what NR calls Cliff Behavioural Unit 17. “It is Horse Cove, and that needs an avalanche shelter-style structure. There is substantial rock bolting and cliff stabilisation also needed here,” explained Gallop.
He was quick to point out that while these schemes improve resilience against extreme weather, it would not guarantee that the railway would always remain open.
“Without this there would be a major closure every year if we don’t do anything,” he said.
“The cliffs from Parsons to Teignmouth are the highest risk. They are the hardest to predict, and they’re monitored visually. We see if they move. We look at the groundwater, which is where the rain has percolated down. We’ll keep the railway safe by closing it if needed.
“We have a trigger level, which is if there is a sudden failure in the cliffs. We’ve not had many - an animal caused the last one.”
Gallop explained that since 2014, NR has spent around £6 million on developing schemes and has a total of £15m to spend. Plans regarding a breakwater to protect the wall have been dismissed.
“We employed consultants from across the world who have said we don’t need a breakwater. If we built that it would disrupt the longshore drift, and it would affect the transfer of sediment.” He said a small site around 100 metres from Marine Parade, Dawlish, would be constructed.
The alternative to these plans was to re-create the cliff slope, he said. “It would need to be confirmed, but the railway would need closing and homes would have to be demolished. We’d considered it, but it would be nonexistent in terms of any financial benefit.”
Discussing the two-month closure of the wall from February 2014 ( RAIL 742), Gallop said: “In 2014, the wall didn’t fail due to the waves, it failed due to the weight of the water and the suction that caused. The suction was such that it collapsed back in.”
Earlier this year the wall was damaged by Storm Emma on March 1 and 2. That damage will be repaired by the end of May, he said. @Clinnick1