White, P.A.; Rosen, M.R.; Reeves, R.R.; Zhan, X.Y. 1998 Heat transport processes in the liner and country rock underlying the Greenmount landfill. Lower Hutt: Institute of Geological & Nuclear Sciences. Institute of Geological & Nuclear Sciences science report 98/06 37 p.
Abstract: A 3D geological model of the Greenmount landfill and surrounding country rock predicts that volcanic lithologies are approximately 10 m thick around the flanks of the relict volcanic cone. Lava spreads from the cone in mainly northwest and westerly direction. Elevated temperatures in the landfill are the cause of increased temperatures in the surrounding country rock. Elevated groundwater temperatures in the surrounding basalt country rock are measured between the water table and 5 m below water table. A coupled flow and temperature model (HST3D), which predicts temperatures in the country rock that are similar to observed temperature data, has liner permeability of 5 x 10-16 m2, basalt horizontal permeability of 3 x 10-11 m2, and basalt vertical permeability of 3 x 10-15 m2. The liner permeability in the model is as measured in the field. Basalt horizontal permeability in the model is as measured in basalt in other locations in Auckland. No field measurements of basalt vertical permeability in the Auckland area are known to the authors. The mechanism of heat transfer in the liner cannot be deduced by this model because predicted temperatures outside the landfill are relatively insensitive to the value of liner permeability. Liner permeabilities in the range 5 x 10-14 m2 to 5 x 10-18 m2 used in the model cover the range between convection-dominant and conduction-dominant heat transfer mechanisms. The dominant mechanism of heat transfer in the basalt is likely to be convection because basalt permeabilities that are required to best match observed temperature values are typical of convection systems. (auth)