Barhale has been appointed to reinforce a section of what was once believed to the longest tunnel in Europe and a key source of raw water for East London.

Selected by Thames Water, the strategically important Thames Lee Tunnel (TLT) was built between 1955 and 1959 to carry water from the River Thames at Hampton Water Works to Lockwood Pumping Station at the Lee Valley Reservoir Chain. The 19-mile (31 km) tunnel runs at a depth of 68 to 190 feet (21 to 58 m) and passes through 24 access shafts of 12 feet (3.7 m) diameter. The tunnel was designed to transfer 120 million imperial gallons (550 megalitres) of water per day.

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Top of Lockwood Shaft, Walthamstow – site for draindown prior to relining of TLT

The contract will see civil engineering and infrastructure specialist Barhale reinforce a 70 metre length of the 2.7m diameter concrete-lined tunnel water main where it runs across the route of HS2 in North London.

The location of the works will necessitate an unusually long concrete pump – 800m horizontal plus the almost 50 metre depth of the Barrow Hill shaft at Primrose Hill – to the site of the works. Barhale has been working with Camfaud to design a bespoke pumping solution.