Abstract:

A number of environmental and stability issues can be caused by a high leachate level in a landfill. Vertical pumping wells can be used to lower the high leachate level. Pumping tests were conducted at a municipal solid waste landfill. Finite element analyses were carried out to simulate the transient flow problem of leachate drawdown. The pumping test gives a hydraulic conductivity of 3.6×10-4cm/s and an influenced radius of about 20m. The numerical analyses show that radius of the pumping well has only a little impact on the pumping efficiency, whereas spacing of the wells is critical to the leachate drawdown. To design a drawdown scheme, spacing of the wells should be determined first considering the demand and time limit of the project. The pump should be selected based on the pumping rate. The radius of the pumping well is then determined by the size of the selected pump. Finally, filter, size of the borehole and type of borer should be determined in sequence.

Key words: solid waste landfill, pumping test, leachate drawdown, transient flow analyses, radius of wells, spacing of wells