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Dunn, J., Russell, C., & Morrissey, A. (1999). Remediating historic mine sites in Colorado. Min. Eng., 51(8), 32–35.
Abstract: This article provides examples of reclamation and remediation in Colorado watersheds. The projects were undertaken by the US Environmental Protection Agency (EPA) Region 8, in cooperation with the Colorado Division of Minerals and Geology (CDMG), Colorado Department of Public Health and Environment (CDPHE), US Forest Service (USFS), the Bureau of Land Management (BLM), Bureau of Reclamation (BOR) and the US Geological Survey (USGS). These agencies collaborated on the environmental problems at abandoned mines. These samples involved the interaction of surface and ground waters with sulfide-bearing rocks, mine workings and surface mine spoils that produce acid solutions charged with heavy metals that are toxic to organisms. In these examples, acid mine drainage from historic mines in Colorado has been approached cooperatively with stakeholders. Each example emphasizes one aspect of the three-stage process. These stages include characterization and prioritization, hydrologic controls and the evaluation of long-term remediation activities.
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Eger, P., Melchert, G., & Wagner, J. (2000). Using passive treatment systems for mine closure – A good approach or a risky alternative? Min. Eng., 52(9), 78–83.
Abstract: In 1991, LTV Steel Mining decided to close an open-pit taconite mine in northeastern Minnesota using a passive-treatment approach consisting of limiting infiltration into the stockpiles and wetland treatment to remove metals. More than 50 Mt (55 million st) of sulfide-containing waste had been stockpiled adjacent to the mine during its 30 years of operation. Drainage from the stockpiles contained elevated levels of copper, nickel, cobalt and zinc. Nickel is the major trace metal in the drainages. Before the closure, the annual median concentrations ranged from 1.5 to 50 mg/L. Copper, cobalt and zinc are also present but they are generally less than 5% of the nickel values. Median pH levels range from 5 to 7.5, but most of the stockpile drainages have pH levels greater than 6.5. Based on the chemical composition of each stockpile, a cover material was selected. The higher the potential that a stockpile had to produce acid drainage, the lower the permeability of the capping material required. Covers ranged from overburden soil removed at the mine to a flexible plastic liner. Predictions of the reduction in infiltration ranged from 40% for the native soil to more than 90% for the plastic liner. Five constructed wetlands have been installed since 1992. They have removed 60% to 90% of the nickel in the drainages. Total capital costs for all the infiltration reduction and wetlands exceeded $6.5 million, but maintenance costs are less than 1% of those for an active treatment plant. Because mine-drainage problems can continue for more than 100 years, the lower annual operating costs should pay for the construction of the wetland-treatment systems within seven years.
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Gusek, J. J. (1995). Passive-treatment of acid rock drainage: what is the potential bottom line? Min. Eng., 47(3), 250–253.
Abstract: Passive-treatment systems that mitigate acid-rock drainage from coal mines have been operating since the mid-1980s. Large systems at metal mines are being contemplated. A typical man-made passive-treatment-system can mimic a natural wetland by employing the same geochemical principles. Passive-treatment systems, however, are engineered to optimize the biogeochemical processes occurring in a natural wetland ecosystem. The passive-treatment methodology holds promise over chemical neutralization because large volumes of sludge are not generated. Metals may be precipitated as oxides, sulfides or carbonates in the passive-treatment system substrate. The key goal of a passive-treatment system is the long-term immobilization of metals in the substrate materials. The passive-treatment technique may not be applicable in all mine-drainage situations. -from Author
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Reisinger, R. W., & Gusek, J. (1999). Mitigation of water contamination at the historic Ferris-Haggarty Mine, Wyoming. Min. Eng., 51(8), 49–53.
Abstract: An historic underground copper mine in Wyoming is discharging neutral but copper-laden water into a pristine creek. The EPA-deferred site qualifies for reclamation by the Wyoming Abandoned Mine Land (AML) program. The cleanup goal is to restore the discharge so that the creek can eventually support a trout fishery. Hydrological and geochemical investigations underground have suggested two sources of mine water: one clean and the other containing copper. Results of bench- and pilot-scale tests support the viability of using low-cost passive treatment techniques to reduce copper concentrations in the near-freezing mine discharge.
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Vegt, A. L. de, Bayer, H. G., & Buisman, C. J. (1998). Biological sulfate removal and metal recovery from mine waters. Min. Eng., 50(11), 67–70.
Abstract: Metalle und Sulfat können aus Grubenwässern in einem zweistufigen biologischen Prozeß entfernt werden. In der ersten Stufe wird das Sulfat durch Bakterien zu Schwefelwasserstoff reduziert. Dieser reagiert mit den gelösten Metallen zu unlöslichem Metallsulfid. Im zweiten Schritt wird überschüssiger Schwefelwasserstoff durch Bakterien zu elementarem Schwefel oxidiert. Eine nach diesem Verfahren arbeitende Anlage wurde 1992 durch die Budelco Zinc Refinery in den Niederlanden installiert. Diese verarbeitet täglich 5000 m(exp 3) Gundwasser. Zur Weiterentwicklung des Verfahrens für die Entfernung von Metallen und Sulfat aus Grundwasser und zur gezielten Kupfergewinnung aus Laugungswässern wurde 1995 in der Kupfergrube Bingham Canyon Utah, USA eine entsprechende Pilotanlage in Betrieb genommen. Anhand dieser Pilotanlage werden der Verfahrensablauf und erste Erfahrungen dargestellt sowie ein Überblick über das Untersuchungsprogramm gegeben.
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