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Mining Information Session State of Alaska and U.S. Environmental Protection Agency

Mining Information Session State of Alaska and U.S. Environmental Protection Agency. Alaska Forum on the Environment Anchorage, Alaska February 12, 2008. AFE 2008 Mining Information Session Structure. Module 1: Introduction & Mining Fundamentals Module 2: Environmental Concerns & Issues

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Mining Information Session State of Alaska and U.S. Environmental Protection Agency

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  1. Mining Information SessionState of Alaska and U.S. Environmental Protection Agency Alaska Forum on the Environment Anchorage, Alaska February 12, 2008

  2. AFE 2008 Mining Information Session Structure • Module 1: Introduction & Mining Fundamentals • Module 2: Environmental Concerns & Issues • Module 3: Agencies & Process • Module 4: Regulatory Framework

  3. Module Overview • Potential environmental impacts from mines • Ways of preventing, controlling, and remediating impacts

  4. Environmental Impacts From Mining • Soil and land-based contamination • Air impacts • Water Quality and quantity • Ground water • Surface water

  5. Ore and Waste A generalized example, based on Fort Knox STRIP WASTE ORE ORE ORE WASTE WASTE

  6. Ground Surface Ore Ore

  7. Ground Surface Waste Rock Ore Ore

  8. Waste Rock Pile Ground Surface Ore Ore

  9. To Mill Waste Rock Pile Ground Surface Ore Ore

  10. Ore Mill Gold Bars or Metals Concentrate

  11. Ore Waste Drystacked Tailings Mill Gold Bars or Metals Concentrate

  12. DAM DAM DAM DAM Wet Tailings Impoundment Wet Tailings Impoundment Wet Tailings Impoundment Wet Tailings Impoundment Ore Waste Waste Drystacked Tailings Mill Gold Bars or Metals Concentrate

  13. DAM DAM DAM DAM Wet Tailings Impoundment Wet Tailings Impoundment Wet Tailings Impoundment Wet Tailings Impoundment Drystacked Tailings WASTE PRODUCTS Waste Rock Pile

  14. Soil and Land-based Concerns • Mining operations can cover large land areas • Waste rock dumps, tailings disposal, roads can impact the land

  15. Soil and Land-based Concerns • Direct impacts: • Physical alteration/loss of habitat and vegetation • Soil contamination • Indirect impacts: • Wildlife • Subsistence users

  16. Soil and Land-based Concerns • Prevention and control measures • minimize footprint • backfill tailings and waste rock • consolidate wastes • reclaim/ revegetate

  17. Air Concerns • Air can be affected by dust or chemical emissions

  18. Dust Issues – sources and impacts • Sources: • open pits and waste piles • ore crushing • roads • Impacts: • air quality • site workers • soil, vegetation, water quality and users of these resources

  19. Dust Issues – prevention/control • Watering roads/piles • Use of dust suppressants • Cover trucks • Pave roads • Control technologies – scrubbers, filters • Reclaim/revegetate

  20. Air Emissions – sources and impacts • Sources: • power sources • heat-using mineral processing technologies • Impacts: • air quality • site workers • vegetation • if metals, sediment and water impacts

  21. Air Emissions – prevention and control • Alternate power sources – wind, solar • Clean power sources • Emission control equipment – scrubbers, filters, adsorption units

  22. Surface Water and Ground Water Concerns • Sources: • underground mine water • open pit mine water • seepage/runoff from waste & tailings disposal sites • sedimentation/erosion from waste & tailings disposal • chemical releases from mills

  23. Acid Rock Drainage (ARD) • Generated when metal sulfide minerals are exposed to air and water. • Tell-tale yellow/orange color of iron deposits • Results in metals dissolved from ore, waste rock, tailings

  24. Acid Rock Drainage Model

  25. Metal Leaching • Metal leaching can occur with ARD or on its own • Contaminants include: • cadmium, copper, lead, zinc • arsenic • selenium • mercury

  26. Surface Water Concerns • Direct impacts: • Sedimentation • Water contamination with acidity, metals, process solutions (cyanide) • Indirect impacts: • Degraded habitat • Toxic and chronic impacts to fish and aquatic life • Food chain impacts: wildlife, human health

  27. Groundwater Concerns • Direct impacts: • Water contamination with acidity, metals • Water quantity reduced during/after mining • Indirect impacts: • contamination of connected wetlands, surface waters • drinking water supply impacts

  28. Surface and Ground Water Impacts • Test mine waste rock and tailings for ARD and metal leaching • Understand baseline environmental conditions

  29. Neutralization Potential (NP) tons CaCO3/1000 tons Acid Potential (AP) Sulfide Sulfur tons CaCO3/1000 tons Static Testing

  30. Humidity Cell Tests This test lasted for 103 weeks before being terminated.

  31. Understanding the chemistry is essential to designing the mine (including waste storage, closure options) Example: Red Dog drainage from waste rock piles must be captured and treated prior to discharge

  32. Surface Water and Ground Water Impacts prevention/control • Goals: • minimize contact between mine wastes and water • maximize water reuse • Prevention/control: • backfill • segregation of reactive rock • water diversion structures • containment – covers, liners • evaporation • collection and treatment

  33. Example water treatment measures - metals • Chemical • precipitation • ion exchange • Biological • wetlands • bioreactors • Physical • settling • filtration

  34. Example water treatment measures - Cyanide • Chemicals are added to cyanide containing wastewater to destroy cyanide • Inco sulfur dioxide process • Noranda copper and ferrous sulfate process • Alkaline chlorination • Hydrogen peroxide • Or cyanide can be recovered • AVR recovery process

  35. Successful Mine Closure • Physical stability to prevent: • potential failures of waste disposal facilities and open pit mines • long-term erosion • Chemical stability to prevent: • poor quality leachate or run-off from waste disposal facilities • poor mine pit water quality or underground mine water quality

  36. Successful Mine Closure • Biological Stability • establish vegetative cover for long term • Land use • long-term ownership and control of mined lands • safe access to mined lands • productivity of the mined lands

  37. Take Home Message- part 1 • Mining operations involve the movement of large quantities of materials that are exposed to environment over long periods of time. • Mining operations can have serious environmental consequences.

  38. Take Home Message- part 2 • There are many ways to prevent contamination from occurring and control or remediate contamination once it occurs. • Key to this: • Understand waste characteristics, water balance, and baseline environmental conditions to understand potential impacts • Minimize footprint and minimize contact with water • Design for closure • Implementation, compliance, and enforcement of environmental regulations (next module)

  39. Pit Mill Tailings Dam & Pond Constructed Wetlands Freshwater Reservoir and Dam Fort Knox MineFairbanks

  40. DAM SAFETY DNRDivision Of Mining, Land And Water/Dam Safety Unit • All dams (tailings and water storage) must be designed to State standards. • Includes seismic standards • Financial assurance for long term care and maintenance

  41. Technical Issues for Dams • Site location and hazard potential • Geology and seismicity • Hydrology and hydraulics • Structural integrity and slope stability • Seepage control • Operations and maintenance • Emergency contingency planning

  42. Recorded Seismic Events and major geologic faults in Southcentral Alaska

  43. Fort Knox Tailings Dam Red Dog Tailings Dam Synthetic liner installation

  44. Water Quality Standards The mission of the Water Quality Standards section is to protect the waters of the State from pollutants.

  45. Classification of Waters 18 AAC 70.020. • (1) FRESH WATER • (A) water supply • (i) drinking, culinary, and food processing; • (ii) agriculture, including irrigation and stock watering; • (iii) aquaculture; • (iv) industrial; • (B) water recreation • (i) contact recreation; • (ii) secondary recreation; • (C) growth and propagation of fish, shellfish, other aquatic life, and wildlife; and • (2) MARINE WATER • (A) water supply • (i) aquaculture; • (ii) seafood processing; • (iii) industrial; • (B) water recreation • (i) contact recreation; • (ii) secondary recreation; • (C) growth and propagation of fish, shellfish, other aquatic life, and wildlife; and • (D) harvesting for consumption of raw mollusks or other raw aquatic life.

  46. Triennial Review (of Water Quality Standards) “Every three years, the Alaska Department of Environmental Conservation (ADEC) conducts a comprehensive review of the Water Quality Standards (WQS) in 18 AAC 70. This review helps to keep the pollution limits for Alaska's waters up to date by integrating the latest science and technology and federal requirements into how the State regulates water quality.” http://www.dec.state.ak.us/water/wqsar/trireview/trireview.htm

  47. Questions and Comments

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