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Acid Mine Spill in Animas River, Colorado
Transcript of Acid Mine Spill in Animas River, Colorado
Gold King Mine
Gold King Mine is one of 23,000 abandoned mines that leak acid waste all over Colorado.
The mining companies had little responsibility for cleaning up after the mines closed, some 100 years ago.
1977 - Surface Mining Control and Reclamation Act required mining operators create a plan for cleaning up closed mines.
Made the mines superfund sites.
Acid Mine Drainage (AMD)
AMD is the result of a propagation cycle:
Why Is This Important?
The propagation cycle of AMD reduces the pH of the water to about 2.5.
Destroys the natural bicarbonate buffering system.
Increases soluble metal concentrations and particulate metals.
Most organisms cannot survive in such acidic conditions.
How Do We Treat AMD?
Time and Dilution.
Adding lime to neutralize the acid and precipitate heavy metals as hydroxides.
Hydroxides form a high density sludge, which once settled gives a clear overflow to discharge into rivers.
Natural recovery is suppressed due to habitat elimination and bio-accumulation of metals in the ecosystem.
What is The EPA Doing about the Spill?
Excavated holding ponds below the breach.
Treat the water with sodium hydroxide and calcium oxide to neutralize the acid.
Leftover sludge is stripped of water and disposed of.
Monitoring wildlife and testing water quality from the mine to New Mexico.
As the contaminated water flows into larger bodies of water, it becomes more dilute.
Acid Mine Spill in Animas River, Colorado
Aug 5, 2015, EPA workers breached a wall of loose debris holding back a pool of waste water from the abandoned Gold King Mine.
Released between 1 and 3 million gallons of acidic, heavy metal laden water into Cement Creek which feeds directly to the Animas River.
The pollution traveled through Durango, CO and Navajo Nation Land in New Mexico, causing warnings against touching the water.
The ironic thing was that the EPA had been trying to slow the leakage of drainage from the mine when their machinery broke through the wall holding back the waste water.
Reaction 1 is the oxidation of pyrite into iron, sulfate and hydrogen
Reaction 2 is the production of iron (III) which acts as an oxidant for the pyrite in reaction 4
Reaction 3 is precipitation of hydrated iron oxide
Reaction 4 produces Iron (II) that is used as a reductant in reaction 2
Reactions 2 and 4 fuel each other
Controlling AMD Migration
Diversion of surface waters flowing towards the site of pollution.
Prevention of groundwater infiltration into the pollution site.
Prevention of hydrological water seepage into affected areas.
Controlled placement of acid-generating waste.
Akcil, A.; Koldas, S. Acid Mine Drainage (AMD): causes, treatment and case studies.
Journal of Cleaner Production
, 14, 1139-1145.
Gray, N. F. Environmental Impact and Remediation of Acid Mine Drainage: A Management Problem.
, 30, 62-71
Niyogi, D.; Lewis, M.; McKnight, D. Effects of Stress from Mine Drainage on Diversity, Biomass,and Function of Primary Producers in Mountain Streams.
, 5, 553-567.
Pappas, S. (2015, August 12). Colorado Mine Spill Aftermath: How to Clean a River. Retrieved September 28, 2015.
Gold King Mine Breach Site
Visible Effects of Acid Mine Drainage
Madelyn Anderson Fraley
Questions to Consider:
Other than adding alkalinity to the contaminated water, what could be done to remedy the pollution in the Animas River?
Is the EPA responsible for the spill, given that the mines were leaking before their equipment breached the waste water barrier?
Should they be held accountable?
Given that the spill occurred while the EPA was trying to plug the leaking acid mine drainage, should the EPA continue trying to fix the other mines' leakage, given that their equipment caused the spill in the first place?
Abanoned Mines in Colorado
Acid Waste Retention Ponds