The objective in designing lining systems for the containment of the leachate generated within a landfill is the prevention of contamination of groundwater and surface waters. The technology involving the design of these systems has progressed to a point that the integrity of the containment can be relied on over the long term. Double-lined systems provide the additional benefit of being able to quantify the performance of the lining system through the detection of leakage through the upper liner. The difficulty, however, lies with the qualitative evaluation of the system. This paper addresses this issue and offers a practical approach for the design and evaluation of double-lined systems and the leakage that is detected.