Research project: Landfill hydraulics

Background

Landfill hydraulics are fundamental to the design and operation of landfills as the flow of leachate through landfills affects leachate management systems and has a major influence on landfill processes, including settlement, gas generation and contaminant removal.

Our research extends back to the early 1990s where our large scale waste testing facility at Pitsea was used to characterise the depth (in the landfill) dependent nature of many hydrogeological properties of waste. This includes permeability (hydraulic conductvity) and porosity.

Subsequent research has demonstrated the large impact that landfill gas generation can have on hydraulic properties.  Gas can cause increases in leachate level (through displacement) and potentially reduces permeability by two order of magnitude.

The novel installation of three 250 m long horizontal leachate wells at a landfill demonstrated the interaction and strongly dependent nature of leachate and gas flows. The use of time lapse surface resistivity was used to track dewatering around one of the wells, and interpretation of the results led to important conclusions about the benefits and limitations of resistivity surveys not previously appreciated within the landfilling scientific community.

More recently hydraulic testing has concentrated on developing an understanding of contaminant transport properties of waste, which includes research into dispersion and the use of tracer tests to characterise how contaminants may be flushed from the waste in the long term.