Researchers at West Virginia University (WVU) have constructed and operated a Rare Earth Element/Critical Material (REE/CM) Facility that extracts, separates and refines high purity rare earth metals from unconventional feedstock. Since 2016, our approach has been based upon a pioneering method using Acid Mine Drainage (AMD) and mineral tailings feedstocks developed in concert with USDOE. These earlier efforts culminated in both a commercial-ready technology package suitable for demonstration-scale deployment as well as an innovation ecosystem and research infrastructure. We project that our demonstration facility will produce between 5.4% and 7.3% of the global requirements for Tb and Dy, two of the most sought after and critical REEs. Our approach additionally imparts a net positive social and environmental benefit, as successful deployment would create several new industries and jobs in the upstream and downstream supply chains while incentivizing the restoration and reclamation of longstanding environmental liabilities. Recently completed and current efforts in the program include pilot-scale production of mixed rare earth oxides, advanced process development for separation and refining, regional economic development, infrastructure, and technology assessment, and the pre-feasibility study for a vertically integrated 1-3 tonnes per day separation and refining facility. We plan to deliver the first fully integrated REE metal production operation in the United States in over 20 years.

In response to the unprecedented environmental challenges of the 21^st century, proposed solutions incorporating the terms “nature” and “natural” have become ubiquitous in the scientific literature and the popular press. Some relevant recent terms include nature-based solutions (NBS), natural infrastructure (NI), and nature and nature-based features (NNBF). In the mine water community, passive treatment systems are prime examples of these applications, although not typically referred to in this manner.

The role of NBS and related efforts is especially relevant in the mining sector, as the global transition to a renewable energy economy requires continued resource extraction, despite decarbonization efforts. Reclamation of mined lands and waters is especially difficult at sites requiring remediation of hazardous materials. In addition, successful reclamation often does not lead to acceptable ecological restoration. NBS, which inherently recognizes the interdependencies of humanity and nature, may be key to linking reclamation, environmental remediation, ecological restoration, and sustainable resource extraction.

Much can be learned from existing NBS applications at derelict mine sites. The Tar Creek (Kansas-Oklahoma, USA) watershed of the abandoned Tri-State Lead-Zinc Mining District is a test bed exploring the links between reclamation, remediation, restoration, and potential future resource extraction. Remediation of source materials has increased dramatically in the past decade and has resulted in the reclamation of previously derelict lands to agricultural uses. Two full-scale mine water passive treatment systems have been installed to address some source waters, producing circumneutral pH, net alkaline effluents containing ecotoxic metals concentrations meeting in-stream water quality criteria. The receiving stream has demonstrated substantial water quality improvement and ecological recovery, with documented increases in both fish species richness and abundance, as well as the return of North American beaver and river otter. The potential for resource recovery from both passive treatment residual solids and the remaining abandoned mining wastes is being explored.

By taking a nature-based solutions approach, legacy mine sites may be able to be restored to functioning ecological systems while closing the resource recovery loop, which informs future resource extraction, whether it be via recycling or sustainable mining efforts. The mine water community is well-served by understanding and incorporating NBS, NI, NNBF and related ideas into life of mine planning.

Mining often requires penetrating the local and regional water table. This creates inflows, which if the area is wet and the country rock significantly permeable, becomes at best a nuisance to operations and at worst an extreme hazard. Effective dewatering creates dry working conditions which are preferable as they reduce risk, reduce wear and tear on machinery, reduce earth moving costs, improve slope stability for open pits and therefore improve safety. Dewatering success is directly linked to a detailed understanding of the groundwater regime enabling application of the best strategy to intercept groundwater inflows. Options available are both passive and active methods including detailed stormwater design, drainage trenches, drain-holes, pit perimeter pumping boreholes (wells), in-pit boreholes, sumps, dewatering galleries, or a combination of methods. A phased approach assists with logically managing the data, information and knowledge flows and their use in dewatering design and implementation.

The potential impact of groundwater inflows should be assessed at the pre-feasibility stage but can be done at any stage of the mine life. A hydrogeological investigation is best tackled in three phases. The first phase is a desktop study to identify the problem, collect site data, create a detailed initial conceptual hydrogeological model then use the information to identify the most practical options for water control.

Phase 2 comprises numerical modelling of the conceptualisation, supported with accurate and interpreted monitoring data. The objective is to use predictive simulations of dewatering options to determine the best strategy for water control. Phase 3 sets dewatering targets to support the mine design, creates an initial dewatering design then implements a prototype to test the concept. Success is evaluated, and the design improved to increase efficiencies. The phased approach is iterative as the conceptual and numerical models are regularly updated, recalibrated with the latest monitoring information, and used to review and implement the dewatering strategy. The monitoring network is continually improved, and the phased approach repeated annually to ensure water control objectives are met for each stage of mining. This paper is an update of the IMWA paper Morton et al (1993) which is still widely read.