Abstract
The objectives of this technical note are to review the gas transport mechanisms through flexible geomembranes, and to measure the methane gas transmission rate, permeance, and permeability coefficient of PVC, LLDPE, and HDPE geomembranes by performing the standard gas transport test (ASTM D 1434). The measured methane gas permeability coefficient through a PVC geomembrane is 7.55×104 ml(STP).mil/m2.day.atm, which is slightly less than the gas permeability coefficient of 8.61×104 ml(STP).mil/m2.day.atm through an LLDPE geomembrane, but slightly higher than the gas permeability coefficient of 3.91×104 ml(STP).mil/m2.day.atm through an HDPE geomembrane. Thus HDPE exhibits a lower gas permeability coefficient than LLDPE. A field design chart for estimating the methane gas transmission rate for different geomembrane thicknesses is proposed using the measured permeability coefficients for PVC, LLDPE, and HDPE geomembranes and Fick's law. This chart can be used by landfill designers to evaluate the methane gas transmission rate for a selected geomembrane type and thickness and expected methane gas pressure in the landfill.
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