Leachate Mound Changes in Landfills Due to Changes in Percolation by a Cap

A simple analytical method, adapted to hand calculations, is presented for evaluating the rise and fall of the leachate level in landfills due to possible changes of recharge caused by a landfill cap. The purpose is to provide an analytical tool for assessing the performance of landfill caps. A constant head boundary is assumed around the perimeter of the landfill, and the two‐dimensional problem is solved using the linearized form of the Boussinesq equation. Percolation from rainfall or from other sources is assumed to be at a steady rate and the only source for leachate generation and mound development. The numerical results from the simple model, in terms of mound rise or decline, as a function of time, were in accord with the solution using the MODFLOW numerical model. The results of the analysis show that the level of the leachate mound is sensitive to changes in the percolation rate, and based on this, it is concluded that the effectiveness of different cap conditions can be assessed by monitoring the leachate level within the leachate mound after cap installation. The analysis is specifically applicable for landfills containing a leachate mound such as landfills in a nonarid environment and where perimeter heads are controlled.