In cold regions, the amplified rate of climate change is altering seasonal cryogenic processes, including the spatiotemporal distribution of seasonally frozen ground (SFG) and snow. These processes are important in the Canadian Maritimes where homeowners in small, rural communities rely on private wells and onsite wastewater (septic) systems during all seasons. More frequent melt events during winter will likely influence pore-water residence time and microbial transport dynamics, potentially threatening groundwater quality and receiving surface waters. To investigate these dynamics, we established a coastal groundwater observatory in a provincial park along the north shore of Nova Scotia, Canada. Preliminary field investigations highlight a shallow water table during the melt season, which we expect to facilitate contaminant transport into groundwater. With field observations guiding two variably saturated hydrologic models, we investigate the impact of these changing cryogenic conditions on wastewater contaminant fate and transport. We adopt a paired modeling approach by combining the Simultaneous Heat and Water (SHAW) model to simulate vertical critical zone dynamics and the influence of snowmelt and ground freeze-thaw, and HYDRUS-2D to simulate deeper, two-dimensional groundwater flow and contaminant transport. Following calibration, the models will be forced with downscaled climate scenarios from NASA (NEX-GDDP-CMIP6). Results from this research will highlight localized threats to groundwater originating from shifts in seasonally frozen ground and snowpack. This research will also be used to evaluate if present design guidelines for onsite wastewater treatment systems can be modified to be more resilient in a changing climate.