Martín Duque, JF, Tejedor Palomino, M, Hancock, G, Martín Moreno, C, Sánchez Donoso, R & de la Villa Albares, J 2022, 'Geomorphic landform design, landscape evolution modelling and geochemical stabilisation for mine closure at the LIFE RIBERMINE project, Spain and Portugal', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 65-78, https://doi.org/10.36487/ACG_repo/2215_01
(https://papers.acg.uwa.edu.au/p/2215_01_Martin-Duque/)
Abstract: The environmental impact of mining on landscape systems is well recognised. New technologies for landscape reconstruction have been developed and advanced in recent decades alongside the recognition of the environmental impact and resultant societal expectation of a restored and integrated post-mining system. A post-mining landscape requires physical stability (and, if present, chemical stability). Australia, the United States, Canada, Chile and the European Union, among others, have mine regulations requiring non-polluting post-mining landforms. We describe mine closure actions in Spain and Portugal (LIFE RIBERMINE project) that integrate two geomorphic landform design techniques: (a) GeoFluv–Natural Regrade, for unconsolidated sandy waste dumps in Spain and pyrite waste deposits in Portugal, and (b) Talus Royal, for hard-rock residual highwalls in Spain. SIBERIA landscape evolution modelling has been used to evaluate the erosional stability of post-mining geomorphic landform designs in Spain. Acid mine drainage (AMD) chemical stabilisation and remediation measures were combined with geomorphic landform designs in Portugal. Design procedures of LIFE RIBERMINE took place in the years 2019 and 2020, being constructed in 2020, 2021 and 2022. Design and construction phases were executed as planned, with minor deviations. The monitoring procedures (lasting until 2029) are intended to verify the real effectiveness of such solutions. The improvement of the water quality downstream in the demonstration site of Spain (Santa Engracia mine, Peñalén) will be quantified by measuring the sediment emission-immission to water bodies. Erosion rate (sediment yield) at the Santa Engracia mine previous to LIFE RIBERMINE was 353 t ha-1 yr-1. The target values after restoration should range between 4 and 15 t ha-1 yr-1, forecasted by the SIBERIA modelling and measured by monitoring similar geomorphic-based solutions at nearby mines. Regarding turbidity, suspended sediment concentrations (SSC) at a pre-rehabilitation phase were 391 g l-1 and target values (baseline) are 24 g l-1. In Portugal (Lousal, Grândola), where AMD is the main problem, it is expected that the dissolved potentially toxic elements’ maximum concentration values of Pb (0.9 mg/L), Cd (0.5 mg/L), Zn (80 mg/L) and Cu (20 mg/L) are reduced to values at least closer to the values established by the Portuguese legislation for minimum water quality in surface waters (Pb – 0.05 mg/L, Cd – 0.01 mg/L, Zn – 0.5 mg/L, Cu – 0.1 mg/L). If the AMD treatment measures are effective, initial physicochemical values of pH (between 1.8 and 3.1) and conductivity (2.71–3.9 mS/cm) should also change to near common non-polluted water values (around pH – 7, conductivity – 0.75 mS/cm). LIFE RIBERMINE aims to significantly reduce mined land environmental contamination and to demonstrate the efficiency of a combination of some best available techniques for mine closure. The performance results can be used to consider applying the innovative rehabilitation and remediation designs to other mine locations, abandoned or active, elsewhere. These project remedies are expected to reduce post-closure expense and liabilities.

Keywords: GeoFluv–Natural Regrade, Talus Royal, acid mine drainage, SIBERIA, LIFE Programme, European Union