Thames Water yesterday celebrated the culmination of a year of crunching through the earth beneath London with the tunnel breakthrough on the southern extension of the city’s so-called M25 for water.
The firm’s 80km-long London Ring Main, a huge circular water main built in the mid 1990s 45m below ground, is Britain’s longest tunnel. However, work started last June on the nearly 5km-long southern extension, running between Brixton and Honor Oak reservoirs, to boost the Ring Main’s daily water transfer capacity by 200Ml.
Following 12 months of tunnelling, a tunnelling boring machine called Helen yesterday broke through into the Ring Main’s existing shaft.
This follows the breakthrough of the northern extension in May, a 4.5km-long tunnel running from Stoke Newington in Hackney to the New River Head in Islington.
The two tunnels, costing a combined £95M, will enable an additional 500Ml of water-a-day to be transferred, helping Thames Water keep up with growing demand in the capital.
“While Londoners have been going about their business above ground, most will have been unaware that for the past year we’ve been grafting away many metres below ground to build two huge water tunnels to help boost our supply capacity for our fast-growing capital city,” said Thames Water chief operating officer Steve Shine.
“The Ring Main, which is basically the M25 for water, delivers 1,300Ml of water around the capital each day. Both new tunnels, one to the north and one to the south of the River Thames, will boost this capacity by 500Ml a day.”
Both tunnels will now be lined with steel and concrete and connected into the Ring Main ready for service in March 2010.