Air Flow as Monitoring Technique for Landfill Liners

Long-term performance of a waste-containment facility liner system can be simply and inexpensively monitored in dry climates by relative humidity measurements. An increase in humidity as atmospheric air is circulated through a dry coarse layer within the liner system indicates imminent movement of water into the layer. Continued airflow will evaporate and remove water, thereby restoring the coarse layer to a dry condition. Thus, quantification of relative humidity and water removal rates can be directly used to assess liner system performance. The effectiveness of this approach is increased in dry climates, where the atmospheric air has a low initial relative humidity and leachate production is expected to be small. Simple calculations, numerical simulations, and medium-scale field tests indicate substantial airflow rates can be induced through a coarse layer within a liner system. Air can be circulated actively with blowers, or passively with wind-powered chimneys. System efficiency can be improved by incorporating a coarse layer that has significant primary storage.