Gas exchangeable properties of "Maharagama" open dump cover soil

In Sri Lanka, normal practice is to dump waste in low lands and cover with a good compacted soil without providing gas venting facilities. This can be found at 'Mahargama' dumpsite too. Once municipal solid waste is placed in landfills, complex sequence of biologically, chemically and physically mediated events occur relating to hazardous gaseous and liquid landfill emissions. Hence, cover soil of landfills/ open dumps plays a major role in emission of landfill gases, because gases are released to atmosphere with high pressure, through cover soil. Therefore, studying gas transport parameters of cover soil are of paramount importance in evaluating its future gas emission. Soil gas diffusion coefficient (Dp)and Air Permeability (ka) govern transport and emission of gases through soil. In this study, these parameters were measured in repacked samples at different water matric potentials. Methane concentrations were measured in site and a methane concentration contour map was produced to identify the gas emission from landfill. According to the observed data, the Maharagama cover soil can be expressed as a less gas exchangeable material (but a good capping soil). In the future methane emission can be increased through the loose compacted points and this can become hotspots. Further, formation of cracks around the ground area will also be possible