The question of how much landfills leak might be the most contentious question in the solid waste industry and the one with the most elusive answer. Leakage can be predicted using models of varying levels of sophistication, but modeling relies on accurate data for hole frequency and size. Published statistics for hole size and frequency vary widely and most of the published data is drastically out of date and out of context for construction practices in North America. The prescribed method of monitoring existing landfill leakage through single-lined landfills is through a groundwater monitoring network, but once contamination is detected it is already too late. The only feasible way of remedying the problem may be to cap and close the portions of the landfill that are leaking, which may jeopardize crucial operating revenue. In extreme cases, groundwater remediation may be required, which is costly and may or may not be effective depending on the hydrogeologic conditions (the types of soil under the site and how the groundwater flows through them). The obvious solution is to build landfill liners that don’t leak, but the simple laws of chemistry and physics, not to mention Murphy ’s Law, preclude this possibility.