Mapping the Vulnerability of Groundwater to Wastewater Spills for Source Water Protection in a Shale Gas Region

Source water protection in areas of shale gas development encompasses identifying areas that are the most vulnerable to groundwater quality deterioration due to spills of natural gas production wastewater. This study uses the density-dependent flow and transport code TOUGH2 to quantify the time and distance of travel of saline wastewater plumes for different hydrogeological settings in Northeast British Columbia. 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. The vadose zone permeability and depth to water table are dominant controls on the wastewater migration rate and footprint. Overall, the vulnerability in the region is relatively low, with exceptions near river valleys and areas with shallow water tables. The vulnerability maps can be used as a preliminary risk assessment tool, as they are based on the main factors influencing the potential of a wastewater spill to contaminate an aquifer.

Automated summary

This study used the TOUGH2 code to quantify the time and distance of travel of saline wastewater plumes in different hydrogeological settings in Northeast British Columbia. The permeability of the vadose zone and depth to water table were found to be dominant controls on the migration rate and footprint of wastewater. Overall, vulnerability in the region is relatively low, except for areas near river valleys and with shallow water tables.