ABSTRACT
To the north the Bloomfield box is bounded by the Circle, Hammersmith and City and Metropolitan line; to the south it is bounded by 46 New Broad Street House. A fault zone was also anticipated across part of the box footprint, although its precise location was unknown. The ejector wells located inside the box began to reduce groundwater pressures during September and October 2014. The use of the observational method (OM) by progressive modification is ideally suited to the implementation of dewatering, especially within the complex geology encountered at the Blomfield Box. An overly conservative design based on the worst credible conditions would have been impractical to install in a single phase while excavating the box in a cost-effective manner. The careful application of the OM by progressive modification minimised delays to the box construction while maintaining an acceptable level of safety.
