Abstract: Sustainable mining is generally considered to be an oxymoron because mineral deposits are viewed as nonrenewable resources that are fixed in the crust. However, minerals are conserved and recycled by plate tectonics which continually creates and destroys ore deposits. Though it is true that rock cycles have much longer periods than biomass cycles, the crust is essentially an infinite reservoir so long as we continue to invest in mineral exploration and processing technology. Implicit in the definition of sustainable development is the recognition that human development of resources in one reservoir may subsequently degrade resources supplied by another. The depreciation of overlapping and adjacent resources is often externalized in the cost to benefit accounting and cannot be sustained if the integrated cost/benefit ratio is greater than 1. The greatest obstacle to sustainability in mining is the expanding scale of excavation required to develop leaner ores because this activity degrades connected resources. In the case of open pit, sulfide ore mining the disturbed land may produce acid rock drainage (ARD). Because ARD will self-generate over the course of tens to hundreds of years the cost of controlling this pollution and rehabilitating mined lands is large and often spread over many generations. Secondary production of minerals from partially excavated deposits where there are preexisting environmental impacts and mine infrastructure help to reduce the risk of depreciating pristine resources, provided that new mining operations “do no (additional) harm” (Margoles, 1996). In turn, a percentage of the profits derived from secondary mineral production can be used for rehabilitation of the previously mined lands. These lands contain significant, albeit low grade, metal concentrations. These concepts are being developed and tested at the Mineral Park Sustainable Mining Research Facility where an in situ copper sulfide mining field experiment was conducted. Monitoring data and computer modeling indicate that ARD is not generated after closure. This is because the ore is not disturbed and is left saturated, whereas unsaturated conditions generate acidic drainage. The short term risk of groundwater contamination is mitigated by utilizing an exempt mine pit to capture any leach solutions that are not intercepted by the wellfield. Using green accounting techniques and transfer models it can be communicated that this mining scenario is an approach to sustainability.

Abstract: The Leadville Mine Drainage Tunnel (LMDT) is a 3.3 kilometer structure that was constructed in the complicated geology of the Leadville mine district in the 1940's. Discharge from the LMDT is impacted by heavy metals and is treated at a plant built in 1992 operated by the United States Bureau of Reclamation. On the surface waste rock and other remnants of the mining operations litter the landscape and this material is exposed to precipitation. As a result of contact with this material, surface water often has pH of less than 3 and its containment and disposal is necessary before it impacts surface drainage and the nearby Arkansas River. Using a borehole drilled into the mine workings the U.S. EPA has devised a plan in which the impacted water is contained on the surface which then can be discharged into the mine workings to discharge from the LMDT and be treated. The percentage of water discharging from the mining district along the drainage tunnel is unknown, and since there is no access, information about the condition of the tunnel with regards to blockages is also relatively obscure. Application of quantitative water tracing using fluorescent dyes was used to model the flow parameters at the scale of hours in the tunnel and evaluate the likelihood of blockages. Because the tunnel has intersected several lithologies and faults, other locations such as discharging shafts, adits and surface streams that could be hydraulically connected to the LMDT were also monitored. An initial tracer experiment was done using an instantaneous injection, which was followed by additional injections of water. Another tracer injection was done when there was a continuous flow of impacted water into the workings. Analysis of the tracer concentration responses at water-filled shafts and at the portal were used to model the flow along the tunnel and estimate several hydraulic parameters. Waters in these settings are mixtures of components with different residence times, so, qualitative tritium data were used to evaluate residence times of decades. The combined injected tracer and tritium data as well as other geochemical data were used to infer the nature of flow and recharge into the tunnel.