Enabling Improved Public Health Protection by Assessing the Vulnerability of Naturally- and Hydraulically-Fractured Aquifers.

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More than 25% of Canadians rely on ground water for their drinking water supply. Many instances of waterborne illnesses are attributed to groundwater sources that were considered safe and became contaminated by pathogens (e.g., Walkerton, ON, May 2000). These disease outbreaks are not randomly distributed; rather they are more likely to occur in fractured rock aquifers. In Canada, 70% of the regional aquifers occur in fractured bedrock, and it is common practice to hydraulically fracture (frack) these aquifers to increase the water yield. This practice can further increase the vulnerability of these aquifers to pathogen contamination due to the induction of hydraulic connections between the aquifer and ground surface. The proposed research combines field- and laboratory-scale experiments with modeling to investigate the effects of fracking bedrock wells on the vulnerability of these aquifers to pathogen contamination. It will focus on the advancement of our conceptual understanding of pathogen transport and retention in fractures. This conceptual, or mechanistic, approach will enable the application of the knowledge gained through this work to different sites and conditions. The following research questions will be addressed: 1) Can fracking a bedrock well induce hydraulic connections between the aquifer and the surface; 2) What is the effect of pathogen size on transport and retention in fractures; 3) What effect does well operation (i.e. pump cycling and flow rate) have on pathogen transport and retention; and 4) How can laboratory-scale findings be linked to the field scale? This research will provide the knowledge required for legislators to develop evidence-based policy regarding source water protection and hydraulic fracturing that directly affects the public health of Canadians. It will also provide practitioners with the knowledge required for developing bedrock aquifer protection plans, and tools for assessing bedrock aquifer vulnerability. Finally, it will provide excellent training opportunities for 10 HQP.