Figure 9.
The graph depicts the relationship between drawdown in metres on the y-axis, ranging from 0 to 20, and hydraulic conductivity in metres per second on the x-axis, ranging from 10 to the power of minus 8 to 10 to the power of minus 1, illustrating recommended dewatering methods for varying conditions. Regions are labelled to indicate appropriate techniques, including Single-stage wellpoints at lower drawdown and moderate conductivity, Two-stage wellpoints and Deepwells at intermediate ranges, and Deepwells at higher drawdown and conductivity. Areas marked Ejector wells and Vacuum deepwells indicate conditions where vacuum assistance is necessary or beneficial. A region labelled Open pumping appears at higher conductivity and low drawdown. The leftmost area states dewatering is not feasible and may not be necessary, while the rightmost area indicates excessive seepage flows, cut-off, or wet excavation may be necessary. Additional notes at the bottom specify where a vacuum is necessary and where a vacuum is beneficial.Revised range of application of groundwater control pumping methods in granular soils, updated from guidance in CIRIA report C750 (Preene et al., 2016) (from Roberts et al. (2023), with permission; in the original figure the horizontal axis is labelled ‘Permeability’ rather than ‘Hydraulic conductivity’)