Herrington, RJ, Alonzo, D, Armstrong, RN, Balboa, CJ, Baniasadi, M, Beltran, A, Brito-Parada, PR, Cording, HM, Creedy, T, Dalona, IM, Dybowska, A, Graham, A, Guihawan, J, Jungblut, AD, Madamba, RS, Magliulo, M, Maulas, K, Mondejar, AJ, Orbecido, A, Paglinawan, F, Plancherel, Y, Prasow-Emond, M, Promentilla, MA, Rasheed, S, Resabal, VJ, Salatino, S, Santos, A, Schofield, PF, Suelto, M, Sumaya, NH, Tabelin, CB & Villacorte-Tabelin, M 2023, 'Development of a site-specific system for the rehabilitation of a former copper mine, Sto. Niño, Philippines', in B Abbasi, J Parshley, A Fourie & M Tibbett (eds), Mine Closure 2023: Proceedings of the 16th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, https://doi.org/10.36487/ACG_repo/2315_091
(https://papers.acg.uwa.edu.au/p/2315_091_Herrington/)
Abstract: Sto. Niño is a legacy mine site located in the Tublay municipality of Benguet District in northern Luzon, Philippines that was closed and abandoned in 1982. The site comprises a former open pit and block caving operation together with rock waste dumps and a tailings storage facility that have had no formal rehabilitation but where local people are now living and farming.  The GCBC DEFRA funded Bio+Mine project commenced in 2022 with the aims of providing an in-depth audit of the abandoned site in terms of geological, hydrological, ecological, and social parameters and to co-design nature and people positive interventions for the regeneration of the mine site together with local indigenous communities.  
Remote sensing, using historic and current satellite data, and new drone deployments using multispectral and lidar cameras were used to develop a baseline assessment of the site. A range of geological and surface water samples were also collected across the legacy mine area, tailings storage facility and the former underground block-caving area where artisanal and small-scale mining operations remain active. Samples were analysed for both their physico-chemical and metagenomic characteristics. Plants on the site were also studied and proved to be an ideal ‘natural laboratory’ for the audit of endemic heavy metal hyperaccumulator plants and invertebrate bioindicators like earthworms. DNA metagenomic sequencing of microbiomes using water, soil and plant root samples was undertaken as well as water from streams, waste dumps and seepages.
Initial findings suggest that Cu and Zn are the only highly elevated trace elements in ground water; levels of As, Cd, Cr and Mo are generally low. However, only two sites yielded water quality potential for domestic use, therefore active biological treatment options are being scoped using metabolic activity of locally naturally occurring bacteria to concurrently (i) increase the water pH, (ii) remove metals, such as Cu, Al, Zn and Mn and (iii) reduce sulphate concentrations.   Several endemic plant species were found to exhibit phytostabilization affinities toward Ni, Zn and Mn and onsite use of these will be investigated. Earthworms were found to be more abundant and diverse in a site where locals had engineered an agricultural plot so use of these as indicators of soil health will be further explored.
Microbiome DNA sequencing will continue to be used to evaluate the impact of mine waste on soil biodiversity in land used for agriculture. These data will also be used for the identification of microorganisms contributing to acid mine drainage but also identify new and native bacteria and fungi that have biotechnological potential and application in biological treatment of water. The soil microbiome sequencing data will help to assess the impact of hazardous metals on soil biodiversity, health and agriculture but also identify potentially beneficial microorganisms to enhance the efficacy of hyperaccumulating plants to remove contaminants from soils.

Keywords: mine rehabilitation, site-specific system, monitoring ecosystem, water quality, social engagement