Long-term observation of alternative landfill capping systems - field tests on a landfill in Bavaria

Abstract

This paper describes large-scale field tests which were conducted in order to test the effectiveness of landfill capping systems. The test setup involved the construction of large-scale lysimeters on a landfill site from which water flowing out of the system can be measured precisely. A simple landfill cap consisting of a thick layer of loamy sand was placed in one of the large lysimeters; the other lysimeter was filled with a more elaborate capping design (1 m of top soil, a drainage geocomposite and a geosynthetic clay liner – GCL). The water balance of the landfill capping system inside each of the lysimeters was measured during a four-year period. The results are presented in this paper. The simple mineral landfill cap in test field 1 had only limited effectiveness in preventing percolation. During the winter months it is inevitable that a large percentage of precipitation percolates through the cap into the landfill. This process resembles groundwater recharge in natural systems. In test field 2, less than 1% of precipitation seeped through the GCL. The landfill capping design of test field 2 proved to be an effective alternative to the standard system as specified in the European regulations.