Natural Attenuation of Acidic Drainage from Sulfidic Tailings at a Site in Washington State
Published:January 01, 1997
R.H. Lambeth, 1997. "Natural Attenuation of Acidic Drainage from Sulfidic Tailings at a Site in Washington State", The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics, G.S. Plumlee, M.J. Logsdon, L.F. Filipek
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Ground and surface water can be contaminated by the transport of soluble oxidation products from sulfidic mine waste impoundments. A program was designed whereby an impoundment that contained sulfidic waste was studied to characterize pore water in the impoundment and to determine the fate of metals as they were transported downgradient. From this information a method to control dissolved metal transport was identified.
An appropriate field site where a sulfidic tailings impoundment was releasing heavy metals into an unconsolidated aquifer was identified and characterized over a 2.5 year period. Twenty-four piezometers and two lysimeters were installed upgradient from, within, and downgradient from the impoundment. Water samples were analyzed for 12 dissolved constituents, and field measurements for pH, redox potential, dissolved oxygen, temperature, alkalinity, and conductivity were made. Dissolution probably results from oxidation of sulfide minerals in the unsaturated tailings; infiltration transports the oxidation products downward through the saturated tailings into the underlying aquifer. Beneath the impoundment, the acidic water is partially neutralized by calcareous strata; pH-sensitive species precipitate as do some oxidized species. Continuing attenuation downgradient from the impoundment correlates mostly to precipitation of and sorption by oxidized mineral species.
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The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics
Environmental issues have become important, if not critical, factors in the success of proposed mining projects worldwide. In an ongoing and intense public debate about mining and its perceived environmental impacts, the mining industry points out that there are many examples of environmentally responsible mining currently being carried out (e.g., Todd and Struhsacker, 1997). The industry also emphasizes that the majority of mining-environmental problems facing society today are legacies from the past when environmental consequences of mining were poorly understood, not regulated, or viewed as secondary in importance to societal needs for the resources being extracted. On the other hand, environmental organizations (e.g., Mineral Policy Center, 1999) point to recent environmental problems, such as those stemming from open-pit gold mining at Summitville, Colorado, in the late 1980s (see Summitville summaries in Posey et al., 1995; Danielson and Alms, 1995; Williams, 1995; Plumlee, 1999), or those associated with a 1998 tailings dam collapse in Spain (van Geen and Chase, 1998), as an indication that environmental problems (whether accidental or resulting from inappropriate practices) can still occur in modern mining. Recent legislation imposing a moratorium on new mining in Wisconsin, and banning new mining in Montana using cyanide heap-leach extraction methods further underscore the seriousness of the debate and its implications for mineral resource extraction.
In this debate, one certainty exists: there will always be a need for mineral resources in developed and developing societies. Although recycling and substitution will help meet some of the worlds resource needs, mining will always be relied upon to meet the remaining needs. The challenge will be to continue to improve the ways in which mining is done so as to minimize its environmental effects.
The earth, engineering, and life sciences (which we group here under the term “earth-system sciences,” or ESS for short) provide an ample toolkit that can be drawn upon in the quest for environmentally friendly mineral resource development. The papers in this two-part volume provide many details on tools in the scientific toolkit, and how these tools can be used to better understand, anticipate, prevent, mitigate, and remediate the environmental effects of mining and mineral processing.
As with any toolkit, it is the professional’s responsibility to choose the tool(s) best suited to a specific job. By describing the tools now available, we do not mean to imply that all of these tools need even be considered at any given site, nor that