A 3D assessment of urban aquifer vulnerability using geological and buried asset models : a case study from Knowsley Industrial Park, NW England

Knowsley Industrial Park, NW England and its buried sewerage network presents a potential source of pollution to the underlying Triassic Sherwood Sandstone aquifer. Weakly permeable superficial deposits beneath the site may provide a barrier to potential pollution of groundwater in the aquifer. The aim of the study was to develop and apply a 3D model of the superficial deposits beneath the park to a qualitative assessment of the vulnerability of the underlying aquifer to potential pollution. The study also aimed to devise a method for the integration of the 3D geological model of the shallow sub-surface with the buried utility network. The 3D model revealed 8 superficial units. Glacial till, comprising clay and silt, was the only weakly permeable deposit identified. Other deposits were interpreted as permeable. The underground utility network was integrated in 3D with the geological model. Those utilities overlying less than 2.5 m of till were interpreted to represent the most vulnerable parts of the underlying aquifer. The greatest relative vulnerability to the aquifer occurred in the south and south-west of the project area. The study identified a novel method for the integration of a 3D geological model and a buried sewerage network. The identification of these utilities prioritised the areas of highest relative vulnerability of the Sherwood Sandstone aquifer to potential pollution from utility leakage. This approach enabled the development of a hazard identification and prioritisation scheme for future improvements to the buried sewerage network serving Knowsley Industrial Park.