New Approach for Ground Water Detection Monitoring at Lined Landfills

The design of a ground water detection monitoring system at a lined landfill is complicated due to uncertainties in contaminant source characteristics and variability of hydrogeological conditions. Maximizing the likelihood of detecting contaminants and minimizing the contaminated area are the conflicting design objectives. Mostly, a large number of wells may be required to achieve the desired efficiency. However, the cost might be quite high from a practical point of view. Moreover, with the conventional monitoring approach, a widely applied three-well monitoring system (minimum regulatory requirement) is more often inadequate to accomplish these objectives at lined landfills due to the limited capture zone of monitoring wells. Therefore, implementation of a new monitoring approach has been proposed in this study to design a highly efficient, cost-effective, three-well system. In this new approach, the main idea is to increase the interception of contaminant plumes at early stages by broadening the capture zone of monitoring well(s) simply by continuous pumping from the monitoring well(s) with a small pumping rate. A hypothetical problem is presented where a Monte Carlo framework is used to incorporate uncertainties due to subsurface heterogeneity and the leak location. A finite-difference ground water model coupled with a random-walk particle-tracking model simulates a contaminant plume released from the landfill for each Monte Carlo realization. The efficiency and the cost of the three-well monitoring network have been compared for conventional and proposed monitoring approaches (PMA). It has been observed that the efficiency of the monitoring system improves significantly by the application of the PMA.