Zortman and Lansdusky Mines

North-Central Montana, United States of America

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Years of Service

1999 to present

Project Description

Historic underground mining on both sites (1884 - 1970's) resulted in underground workings and tailings that were deposited directly into stream channels. The Zortman and Landusky mines were the first large scale, valley heap leach operations in mountainous terrain. Modern mining and leaching operations started in 1979 and continued until 1995. Gold and silver were extracted by Carbon Absorption and Stripping and Merril-Crowe precipitation. Both sites consist of a series of open pits and associated leach pad complexes and waste dumps. A total of ~15 million tons of waste rock (and dike fill) and 140 million tons of spent ore on lined pads was produced. Most of the waste rock and spent ore is acid generating requiring collection and treatment of all waters draining from the mine disturbed land. Economic failure of the operator resulted in the mine closing in 1995 and current reclamation efforts are under the direction of the Montana DEQ using the Closure Bond Funds provided by the operator under Montana bonding requirements.

Services Provided

Robertson GeoConsultants were subcontracted to Spectrum Engineering Inc. out of Billings, Montana as part of the team responsible for site characterization and the development and comparative analysis of reclamation alternatives for both mine sites, and the implementation of the selected reclamation measures.

Services include aspects of site and mine waste investigation and characterization (geochemical and physical characterization as well as water quality assessments); reclamation cover modeling and assessment of various cover types; leach pad water quality predictions and evaluation of management options; engineering and design of potential reclamation alternatives; evaluation of the various alternatives using a Multiple Accounts Analysis (MAA) taking into account the positive and negative impacts of the various alternatives with respect to technical, economic, environmental and socio-economic issues; and, development of portions of the Site investigation work included a number of drilling, sampling and testing programs for:

  • drilling and sampling for geochemical characterization of the heap leach spent ore and leach pad dikes;
  • laboratory test programs for the determination of acid generating potential of mine waste, spent ore, pit complexes etc.;
  • investigation of surface and groundwater conditions and prediction of future water qualities

Engineering evaluations and designs included

  • geochemical modelling of solutions associated with waste dumps and heap leach pads (Minteq and Phreeqe).
  • cover modeling (using SoilCover and SEEPW software) of various reclamation cover scenarios
  • geochemical mass balance modelling
  • Multiple Accounts Analysis (MAA) of reclamation alternatives and preparation of portions of the Supplemental Environmental Impact Statement (SEIS) for reclamation of the sites.

Dr. Robertson and Ms. Shaw participated extensively in numerous meetings and with Regulatory Authorities (US BLM, MT DEQ and US EPA) as well as technical and public meetings with various stakeholder groups.

Papers

Shaw, S.C., Robertson, A. MacG., and Maehl, W.C. (2000) Material Characterization and Prioritization of Remediation Measures at the Zortman/Landusky Mine Sites. In: 2000 Billings Land Reclamation Symposium. March 20-24, 2000 Billings, Montana p. 346-358.

Shaw, S.C. (2000) "Geochemical Characterization and Water Quality Predictions for the Zortman/Landusky Reclamation Project". In: Mine Design, Operations and Closure Conference 2000.

Shaw, S.C, Robertson, A. MacG., Maehl, W.C., Kuipers, J. and Haight, S. (2001) : Review of the Multiple Accounts Analysis Alternatives Evaluation Process Completed for the Reclamation of the Zortman and Landusky Mine Sites. In: National Association of Abandoned Mine Lands Annual Conference, August 19-22, 2001, Athens, Ohio.

Wels, C., Loudon, S. and Newman, G. (2001) : Modeling of Alterntive Cover Scenarios for Mine Rock Piles at the Zortman and Landusky Mine Sites. In: National Association of Abandoned Mine Lands Annual Conference, August 19-22, 2001, Athens, Ohio.

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