TCE and PCE diffusion through five geomembranes including two coextruded with an EVOH layer

Aqueous diffusion of trichloroethylene (TCE) and tetrachloroethylene (PCE) is examined for high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polyurethane/urea, and two polyethylene (PE) geomembranes coextruded with ethylene vinyl alcohol (EVOH). Additionally, the diffusion of benzene, toluene, ethylbenzene, and xylenes through polyurethane/urea geomembrane is examined. Permeation coefficients for HDPE, LLDPE, and polyurethane/urea range from 0.4-1.2 × 10⁻¹⁰ m²/s for TCE and 1.0-2.5 × 10⁻¹⁰ m²/s and for PCE. Experiments using the coextruded geomembranes have not reached equilibrium at 500 days, however parameters for the EVOH layer are deduced using data from these experiments. Using the parameters of the individual layers, single layer parameters were calculated. These single layer parameters range from 0.37-2.2 × 10⁻¹² m²/s for TCE to 0.28-0.93 × 10⁻¹² m²/s for PCE. Two hypothetical vapour intrusion cases are modelled using the parameters developed for the five geomembranes, and the calculated airspace concentrations decrease depending on the choice of vapour barrier in the following order: no barrier >0.75 mm LLDPE >1.5 mm polyurethane/urea >1.5 mm HDPE >0.75 mm LLDPE/EVOH/LLDPE >1.5 mm HDPE/EVOH/HDPE.