Characterizing Groundwater Quality and Bacterial Community Composition in Chloride Impacted Drinking Water Wells in Sherman, CT.

The following chapters of this thesis are written with regards to the hydrogeologic investigations of the anthropogenically impacted fractured bedrock aquifer located in Sherman Connecticut. Several domestic and public water supply wells in the town center have consistently exhibited concentrations of chloride and sodium above state and federal drinking water standards over at least a four-year period. Using multiple methodologies and analysis to characterize subsurface conditions and flow pathways provides a greater understanding of the controls on water quality in the town center. Through the analysis of geochemical trends, spatial distribution of well locations and construction along with geologic context, precipitation trends, and through the application of next generation gene sequencing of bacterial populations, interpretations of groundwater recharge zones and flow pathways controlling water quality are made. Several possible mechanisms that store sodium and chloride in the subsurface are proposed to explain the persistence of these solutes in groundwater. The application of next generation sequencing to characterize bacterial communities in well water provides a novel look at the implications for using bacterial communities to make interpretations of groundwater conditions in the context of this hydrologic system. Using all these methods to understand flow paths and controls on groundwater quality paints a more complete picture than the application of just one dataset. This understanding has implications for mediating such impacts and the preservation of drinking water quality in any fractured bedrock aquifer utilized for drinking water