Modelling wastewater spills and mapping areas most vulnerable to groundwater quality deterioration in northeast British Columbia

This study utilized numerical modelling of spills and leaks of natural gas production wastewater into the shallow subsurface to identify areas most vulnerable to groundwater quality deterioration in Northeast British Columbia. Modelling was conducted using the flow and transport code TOUGH2. The models were designed to address three main factors identified from the DRASTIC method for vulnerability assessment: (1) Depth to water, (2) Impact of vadose zone, and (3) Conductivity of the aquifer materials. Models show that dense saline wastewater will migrate further and faster through highly permeable materials. Lower permeability materials attenuate the wastewater migration resulting in smaller plumes with locally higher brine concentrations. A sensitivity analysis reveals that the vadose zone permeability and depth to water table are significant controls on wastewater migration and footprint. Overall, the vulnerability in the region is relatively low, with some exceptions near river valleys, mountainous regions, and areas with shallow water tables.