Design of low permeability seepage barriers to control groundwater flow between mine sites and rivers

Wendy Timms (ACSMP) and Steve Bouzalakos (ACSMP) in affiliation with the National Centre for Groundwater Research and Training (NCGRT)

 A low permeability barrier (LPB) can be constructed to limit inflow to a mine, control horizontal seepage and/or process water with potential contaminants, and discharge from mine sites to surface water sources.

In this study by ACSMP and NCGRT researchers, an optimum mixtures of soil from a local mine site, and bentonite clay were determined based on compaction, geotechnical centrifuge testing and numerical flow modeling of LPB scenarios between an open cut mine and a river. Laboratory testing indicated that the cost of constructing such a barrier could be reduced by more than $1 million with careful design and construction.

A computer groundwater model was then developed to represent an open cut mine near a river, with scenarios including no barrier, and several different designs of barrier. The variably saturated model indicated that groundwater flow towards the pit was sourced from dewatering near the pit, rather than from induced leakage from the river. Further work is required to verify the long-term performance of this soil-bentonite mixture and the risk of LPB failure if permeated with poor quality water.

The most recent research results were presented by Dr Wendy Timms at the International Water in Mining conference in Chile (Bouzalakos et al. 2014), and at the International Congress on Physical Modelling in Geotechnics in Perth (Timms et al. 2014). A journal paper on geotechnical centrifuge methods for testing low permeability materials under realistic conditions was recently published in the Hydrological and Earth System Sciences Discussion journal.