Ring Main: Southern extension
The southern route runs 3.1 miles from Honor Oak, one of our underground reservoirs, to Brixton.
Shaft sinking in Thanet Sand formation, September 2007
Work started in June 2007 and 12 months of tunneling work was completed in August 2009. Tunnelling has been delayed slightly due to troublesome ground conditions which have resulted in severe wear to the cutter head of the tunnel boring machine.
Prior to tunnelling, ground investigations were conducted using boreholes, to identify the ground conditions. Further studies were undertaken to confirm the location of underground services and the presence of deep foundations. Using this information we determined the final routes of the tunnels.
The tunnel is 4,850 metres long and approximately 45 metres below the surface, well below the depth of any service pipes or cables and the London Underground.
The tunnel will be lined with steel and concrete and connected to the Ring Main ready for service in March 2010.
