A low permeability barrier (LPB) is an underground vertical wall constructed to control horizontal seepage and/or process water with high content of salts and other potential contaminants. This study provides a useful overview of LPB installations at mine sites in Australia and internationally, an outline of best practices and preliminary laboratory testing and numerical modelling to optimise LPB design at a hypothetical site.The steps in effective LPB design and construction can include: site surveys and laboratory tests of geology, permeability and water-barrier interactions, computer modelling and prediction in some cases, followed by site construction and testing to appropriate standards and monitoring of barrier effectiveness. Examples are provided of laboratory tests for permeability and modelling of subsurface flow between an open pit and a river. The sensitivity of permeability (to a target hydraulic conductivity (K) of 10-8 m/s) and total flow to the percentage of bentonite clay in the construction mix was evaluated. It was demonstrated that a relatively small percentage of bentonite or soil could significantly decrease permeability. Doubling the bentonite in the mix from two to four per cent decreased the K by an order of magnitude. Preliminary models of variably saturated flow of a hypothetical site using the HYDRUS-2D code indicated that an LPB could significantly reduce subsurface flow, changing the distribution of water storage on both sides of the barrier.Application of best practice for mine site LPB are increasingly important given the sensitivity of rivers and wetlands to mine discharge, barrier construction costs of millions of dollars, and the need to verify the effective performance of barriers over years and decades.CITATION:Timms, W, Liu, H and Laurence, D, 2013 Design of low permeability barriers to limit subsurface mine water seepage, in Proceedings Water in Mining 2013 , pp 57-66 (The Australasian Institute of Mining and Metallurgy: Melbourne).