HS2 engineers unearth ancient coastline in West London

Engineers delivering Great Britain’s high speed rail network (HS2) have unearthed an ancient, sub-tropical coastline dating back 56 million years.

In Ruislip, West London, a HS2 investigation team excavated unknown material thought to stretch 33 metres below ground. It was a coat of black clay – dubbed the ‘Ruislip Bed’ by HS2 Ltd – formed when densely wooded marshland grows on the periphery of a sub-tropical sea.

It was certainly a surprising find for the investigation team, who were busy assessing ground conditions ahead of the Northolt Tunnel construction – a 14 kilometre straight running from West Ruislip to Old Oak Common.

Of the discovery, Dr Jacqueline Skipper – geological expert from Geotechnical Consulting Group – said: “Although ground investigations regularly take place across the country, it’s really exciting and very unusual to come across a material that no-one has ever seen before. The ‘Ruislip Bed’ discovery is particularly fascinating, as it is a window into our geological history.

“It would have been formed during the Paleocene period, which was a time of intense change, with new animals evolving following the extinction of the dinosaurs. Most of Southern England was covered by a warm sea and this clay helps us to pinpoint where the coastline was.”

Meanwhile, Steve Reynolds – Ground Investigation Programme Manager for HS2 – added: “Since 2015, we have been investigating ground conditions along the route of HS2, so we can design the railway in the safest and most efficient way.

“We have been exploring the soil and rocks beneath the surface through various methods, ranging from drilling into the ground and taking samples to using radar technology. Our main investigations are almost complete, with over 1 million laboratory tests undertaken on the samples we have taken. It’s the largest ground investigation programme that the UK has ever seen and an unparalleled opportunity to learn about the ground beneath our feet.”

The initial ground investigation programme for Phase I – spanning London to the West Midlands – will be mostly complete by March 2018. A supplementary, targeted investigation – led by HS2 Ltd’s construction partners – will then follow.

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