Assessing risk to groundwater quality using an integrated risk framework

Risk to groundwater quality is defined as a function of susceptibility, hazard and consequence. Aquifer susceptibility combines the intrinsic susceptibility of the physical system with potential preferential pathways. Hazard threats are assessed based on the potential impact and probability of release. The consequence is the financial cost of the loss of the resource. The risk assessment methodology is applied to the Township of Langley, BC. The results define vulnerable areas as those where susceptible aquifers coincide with chemical and biological threats. The risk is greatest where vulnerable areas coincide with high potential financial loss: within municipal well capture zones and where wells serve high value agriculture. A regional numerical model was constructed and used to outline capture zones for wells that may be at risk. The model was also used to model contaminant transport and highlight the need to consider horizontal groundwater flow when assessing vulnerability.