Geomorphic-based restoration and transition planning for the Ilmenitas waste rock dump in Minas de Riotinto, Spain

Authors: Sanjuan López-Cózar, EJ; Martín Duque, JF; Tejedor Palomino, M; Jiménez Molina, D

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DOI https://doi.org/10.36487/ACG_repo/2515_81

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Sanjuan López-Cózar, EJ, Martín Duque, JF, Tejedor Palomino, M & Jiménez Molina, D 2025, 'Geomorphic-based restoration and transition planning for the Ilmenitas waste rock dump in Minas de Riotinto, Spain', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-15, https://doi.org/10.36487/ACG_repo/2515_81

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Abstract:
The Minas de Riotinto mining district, located in Huelva, Spain, within the Iberian Pyrite Belt, is a historically significant mine site that presents unique environmental challenges due to its legacy of extensive mining and waste deposits rich in sulphides. This paper presents the restoration and closure example of the ‘Ilmenitas’ (ilmenite) waste rock dump (WRD), intended to also help mitigate acid mine drainage; mostly by removing potentially acid forming (PAF) materials and sealing the remaining deposit, reducing its water erosion potential, increasing geotechnical stability and promoting long-term ecological recovery. The project also embraces modern transition planning principles, repurposing the WRD site to accommodate a future regional road while also augmenting social and economic value. The project included: (a) a plan for removing ilmenite waste deposits from the WRD; (b) the geomorphic landform design (GLD) of part of the WRD, using the GeoFluv method and related Natural Regrade software, to transform WRD outslopes into future road embankments; (c) comparing the geotechnical stability of the existing outslopes of the WRD with the projected geomorphic landforms of the road embankment by using SLIDE software; and (d) addressing proper soil amendments and revegetation. Specific outcomes of the project were a detailed plan for removing more than 100,000 m3 of ilmenite, sealing the remaining deposit and for the GLD of 18 ha of WRD outslopes to be reshaped as road embankments. In terms of geotechnical stability, these showed an enhancement of factor of safety close to 50% for the west embankment and more than 30% for the east one. The project was completed with the cover of the newly designed fluvial channels with limestone, becoming open limestone channels, an organic matter amendment of 30 t ha−1, and a seeding plan of grasses and legumes with a dose of 30–35 g/m². The entire removal of ilmenite and a first phase restoration were carried out in 2024. First monitoring results showed high stability in terms of water erosion and a reduction from 7,480 to 5,570 μS/cm in electrical conductivity, which indicates a decrease in the total ionic load of the system. For comparison, baseline values are 10,000–12,000 μS/cm. Also, there is a significant decrease in sulphate concentration (SO₄²⁻), from 8,580 to 5,220 ppm (baseline 9,000–12,000 ppm). This project, which continues in 2025, intends to represent a pioneering restoration approach as it integrates road infrastructure on top of a WRD, setting a model for sustainable post-mining land use that balances ecological, social and economic goals.

Keywords: Iberian Pyrite Belt, geomorphic restoration, transition planning, Minas de Riotinto, acid mine drainage, sustainable post-mining

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