Transit-time design of earthen barriers

Abstract Transit-time analyses are used to evaluate the design thickness of earth-lined waste containment barriers. Solute transit times are determined from dimensionless charts based on an existing analytical solution for transient solute transport in saturated porous media. Both solute concentration and solute flux are considered in the transit-time analyses. With respect to solute flux, a dimensionless parameter termed the “flux number” is introduced. The results of an example design problem using measured parameters indicate that the effects of diffusion and retardation on solute transit times can be significant in low-permeability (i.e.,≤ 1.0 · 10−9m/s), fine-grained barrier materials. The method is relatively simple and can be used for preliminary design of earthen waste containment barriers, evaluation of remedial measures, and/or verification of more sophisticated numerical models.