Geoenvironmental impacts of construction dewatering

Bevan, Marc A (2005) Geoenvironmental impacts of construction dewatering. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Designing a suitable construction dewatering system can be difficult where ground conditions are uncertain. Furthermore, uncertainty relating to the performance of a construction dewatering system can also add complexity to an assessment of the environmental impacts.

Numerical models were used to investigate the influence of inhomogeneities in the Chalk on the performance of a large-scale construction dewatering system. It was found that permeabilities in the Chalk varied considerably within a large excavation. In addition, anisotropy was shown to be influential when dewatering within cut-off walls.

The potential environmental impacts of construction dewatering include saline intrusion and contaminant migration. Numerical models were used as a tool for interpreting groundwater quality data collected during the construction period. The modelling suggested that significant saline intrusion occurred as a result construction dewatering. Migration of cement kiln dust leachate may have also taken place, although concentrations were probably strongly attenuated by mixing and in some cases by ion exchange.

Consideration was given to the suitability of site monitoring programmes, in particular the location of monitoring wells, the sampling period and the vertical migration of contaminants caused by drilling of boreholes.

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