Effects of leakage rate and liner seam orientation on detection monitoring configurations at waste impoundments

A modeling study examined the effect of leakage rate and liner seam orientation on configurations of contaminant detection wells in groundwater. Monitoring networks took into account the unknown location of a future release, and a higher risk of leakage at liner seams, for different combinations of leakage rate and seam orientation. Derived networks comprised two arrays of wells, one relatively close and the other farther away from the landfill, capable of detecting all releases before associated contaminant plumes reached a property boundary. A smaller (more efficient) monitoring network was found for seams oriented more parallel to groundwater flow. Based on outcomes of this study, landfill designers should consider: (1) benefits of seams oriented parallel to groundwater flow, weighed against possible drawbacks of more seams or greater total seam length; and (2) small holes and leakage rates in conventional liner systems producing narrow contaminant plumes, warranting closely-spaced monitoring wells.