Channel Tunnel Rail Link (HS1)

The UK’s first High Speed rail line, built to connect London’s St Pancras station with the Channel Tunnel at Folkestone was the largest civil engineering project in Europe at the time. WJ were involved in a number of groundbreaking schemes across the length of the project including several UK dewatering records – the largest deployment of an ejector system (2000 lin m for the Ashford International Station), largest single dewatering contract ever undertaken in the UK by value (12.2M GBP in 2025 prices) for the Thames Tunnel and deepest dewatering wells drilled (175 m for London Tunnel West). 

The project was a showcase for WJ’s dewatering prowess at the extremes of what is possible – the very high permeability of the Thames Terrace gravels overlying highly fractured chalk at the south portal of the Thames Tunnel at Swanscombe, resulting in peak abstraction flows in excess of 500l/s to the extremely low permeability of the Weald Clay at Boxley Tunnel where our ejector system yielded just 1l/sec from tiny fissures over 300 linear m of cut and cover tunnel, but nevertheless obtained over 12 m drawdown which was required to ensure slope stability during the construction phase.