Depressurisation and surface settlement at Vallance Road Garden, Whitechapel

In 2011 BBMV C510 Joint Venture was awarded the contract for the construction of the Vallance Garden Crossover tunnel. Originally the Crossover was located in Fisher Street, but in 2011 it was relocated to the Vallance Garden area. Due to a lack of geological information a total of 9 bore holes were drilled during summer 2012 (WH58 to WH66). Figure 2 shows the plan view of Vallance Garden Site investigation. Bore hole WH59 had to be drilled twice (WH59a) due to design change of the Cavern Eastbound clashing with the originally drilled WH59. At the location of borehole WH64 an obstruction was encountered at 2.6mbgl which necessitated multiple drill attempts.