Wastewater impacts on groundwater at a fractured sedimentary bedrock site in Ontario, Canada: implications for First Nations’ source-water protection

Marshall, Rachael E.; Levison, Jana; McBean, Edward A.; Parker, Beth

Wastewater impacts on groundwater at a fractured sedimentary bedrock site in Ontario, Canada: implications for First Nations’ source-water protection | Impacts des eaux usées sur les eaux souterraines au niveau d’un site de substratum rocheux sédimentaire fracturé en Ontario, Canada: répercussions en terme de protection des sources d’eau des Premières Nations Impactos de las aguas residuales en las aguas subterráneas de un basamento sedimentario fracturado en Ontario, Canadá: implicancias para la protección de las fuentes de agua de las Naciones Originarias 加拿大安大略省破碎沉积基岩场地废水对地下水的影响:原著民水源保护的影响 Impactos de águas residuais em um aquífero sedimentar fraturado em Ontário, Canadá: implicações na proteção das fontes de água das Primeiras Nações

2019

Marshall, Rachael E. | Levison, Jana | McBean, Edward A. | Parker, Beth

The impacts of wastewater on Indigenous drinking water sources is an issue of concern across Canada. This study investigated the wastewater impacts on groundwater resources at a First Nations reserve located on a vulnerable fractured sedimentary bedrock aquifer in southern Ontario. The objectives were to examine the spatiotemporal variability of a variety of tracers of wastewater and their movement to groundwater. The tracers included nitrate, E. coli, total coliforms, and the artificial sweeteners sucralose, acesulfame, and cyclamate. Isotopes in the groundwater were also examined, including tritium and the isotopes of oxygen and nitrogen in dissolved inorganic nitrate. Three multilevel monitoring systems (seven-channel continuous multi-channel tubing) were retrofitted in unused drinking-water wells on the reserve and monitored from December 2015 to November 2016. Results indicate that groundwater at various depths has been impacted by the septic systems on the reserve. The fractures intersected by the three retrofitted wells contain a mix of newly recharged and older water, and contaminant peaks do not always correspond with ports aligned with higher hydraulic conductivity, showing variable travel times for the constituents. The selection of wastewater management systems that are appropriate for the particular hydrogeological setting on the reserves is critical to providing safe, clean drinking water to Indigenous communities. In particular, special consideration should be made for communities situated on fractured sedimentary bedrock aquifers with thin overburden.

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