Variation in permeability and dewatering performance for part of the Crossrail route in east London

The purpose of the ground investigations was to aid in the design of the portals (North Woolwich & Plumstead), Woolwich Box Station and modification of the existing Connaught Tunnel. The main aims of the investigations were to confirm the ground conditions and conceptual model for the site, observe ground movements during pumping tests, provide data on groundwater levels and tidal influences and to provide data on groundwater pumping characteristics to aid the design of a dewatering scheme during construction. The pumping tests were required to assess the potential yield and hydraulic properties of the multi-layered aquifer system, which comprised Drift Deposits overlying Thanet Sand (where present) and Chalk Formation aquifers. Also it was intended that the tests would permit a more accurate estimate of the number of wells and supporting piezometer monitoring installations required during construction. All locations are among dense urban infrastructure and surface/sub-surface structures.