Iron Mountain Mine California Acid Mine Drainage Discharge

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Iron Mountain MineCaliforniaAcid Mine Drainage
Discharge
Stuart Gaunt Guy Laurie
2
Location

• Iron Mountain Mine is located in Shasta County,
  in the state of California in the south-eastern
  foothills of the Klamath Mountains.
• Roughly 9 miles northwest of the city of Redding.

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History of the Site

• Mining at Iron Mountain began in the mid 1850s
  and ended in 1963.
• The site compromised of approximately 1,800
  hectares.
• California state record indicate that between
  1888 and 1965 the mines yielded
• 313 million pounds of copper
• 265,314 ounces of gold
• 24 million ounces of silver
• 2.6 million pounds of sulphur
• Vast quantities of zinc and iron
• By the time mining operation ceased work in 1963,
  10 separate mines were excavated on the site.

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How bad was the AMD Discharge?

• The mining activity provided an effective means
  of both water and air to reach the sulphide
  deposits producing sulphuric acid and dissolving
  the heavy metals in the ore.
• The uncontrolled acid mine drainage was the
  largest source of surface water pollution in the
  United States.
• Accounted for 25 of the entire national
  discharge of copper and zinc to surface waters
  from industrial and municipal sources.
• According to EPA documents, workers once
  inadvertently left a shovel standing in the green
  liquid flowing from one of the mine portals. The
  next day half the shovel had been eaten away.

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Social and Environmental Effects

• The pollution did not threaten the lives of the
  human population in the area.
• Many aquatic life forms downstream of Iron
  Mountain have struggled for survival particularly
  fish due to the potential contaminant
  accumulation.
• There has been a steady decline in the fish
  population in the area, an example being the
  listing of the endangered species list of the
  Winter Run Chinook Salmon.

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High Runoff Storm Events

• High runoff storm events resulted in major
  releases of heavy metals.
• Dissolved copper concentrations in the Sacramento
  River reached 13 parts per billion.
• The river went from its normal pH value of 7.5 to
  6.
• Acid mine drainage from Iron Mountain killed
  100,000 or more fish on separate occasions in
  1955, 1963 and 1964.
• 47,000 trout died during in a one week period in
  1967.

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Clean-up

• The Slickrock Creek Dam captures acid mine
  drainage escaping from fractured bedrock and
  buried mine portals along the south side of Iron
  Mountain.
• Dredging approximately 200,000 cubic yards of
  copper and zinc contaminated sediments from the
  Spring Creek Arm of Keswick Reservoir.
• Water Management
• Capping selected cracked and caved ground areas.
• Diverting a number of creeks in the area around
  waste rock and mine tailing piles.
• Performing hydro-geologic studies and field-scale
  pilot demonstrations to better define the
  feasibility of controlling acid mine drainage
  formation.

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AMD Discharge Clean-Up

• In 1992, the EPA selected an interim remedy to
  treat the acid mine drainage discharges by
• constructing collection and conveyance systems.
• constructing a lime neutralization treatment
  plant.
• The treatment plant has been built and has been
  operating since 1994 and will continue, until an
  alternate remedy could be developed to assure
  meeting all cleanup goals.

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Economic Effects (Settlement Costs)

• In 2000 a settlement was reached with Aventis,
  the principal responsible party at IMM.
• The total value of this settlement, for past
  costs and future work is over 950 million.
• Under the terms of the settlement,
• 200 million for the first thirty years of site
  activities
• 100 million in cost overrun insurance
• a balloon payment of 514 million in 2030, which
  the EPA or State of California may use to fund
  future activities.
• 8 million payment to EPA for future site costs
• 10 million payment for natural resource
  restoration projects, such as wetlands
  restoration
• This was one of the largest settlements with a
  single private party in Superfund history

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Summary

• EPAs cleanup and pollution control measures
  have been very successful and have reduced the
  discharge of acidity, copper, cadmium and zinc by
  95.
• However, USGS scientists estimate that at current
  erosion rates, Iron Mountain will continue to
  produce acid mine drainage for 2,500 to 3,000
  years, until the estimated 12 million tons of
  sulphide deposits remaining within the mountain
  have weathered away.
• Any Questions?