Conceptual hydrogeological model for a landfill in a floodplain environment: case study of the JV Industries and Fairway Landfill, Shxwhá:y Village First Nation, Chilliwack, B.C.

Abstract

The characteristics of floodplains of major rivers are of interest to many shoreline communities due to issues related to flooding, water demand, and land use. Studies of the hydrogeological conditions within these environments can improve our understanding of these settings. The case study of the JV Industries and Fairway Landfill, located within the floodplain of the Fraser River, highlights the complex groundwater flow dynamics in such an environment. In particular, the study examined the potential for substantial changes to both groundwater flow and groundwater quality during or immediately following the spring freshet due to the presence of permeable, extensive, and hydraulically well-connected floodplain deposits. During spring and early summer, groundwater flow across the landfill is controlled primarily by the Fraser River freshet and the direction of flow varies spatially across the site. During the winter, groundwater flow is controlled primarily by regional topography and is directed to the southwest towards the nearest topographic depression, the remnant Coco-oppelo Slough. In the intervening months, the flow directions are transitional between the winter and spring – early summer flow patterns. The changes in the groundwater flow patterns were inferred to temporally affect the groundwater quality downgradient of the landfill.