ABSTRACT
Landfill caps have to prevent infiltration of rainfall into the disposed waste, enable controlled gas collection, and often must be suitable for recultivation. Furthermore they must be long-term effective and resistant against loads and stresses such as subsidence, erosion, biopenetration, frost, desiccation and clogging of the drainage system. The basic concept for the determination of the water balance of these systems is the use of clearly-defined test fields, so called lysimeters. Within a lysimeter, precipitation as well as soil water content and all the discharges across the lysimeter boundaries are measured, while uncontrolled inflow into the test field has to be prevented. Quality assurance begins with the selection of materials and technology, ends with the end of construction, and should be followed by some kind of long-term monitoring. The research and development program was started in 1986. It took one year to plan the test fields and another year to build them.
