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The Gold King mine, located in the San Juan Mountains of
Colorado, last operated in 1922 but has been in the news in recent
years due to an unwanted legacy that had been slowly building up
in the abandoned gold and silver mine. The legacy was acid mine
drainage. In 2015 officers from the United States Environmental
Protection Agency (EPA) investigating a slow leak at the mine
entrance, accidently released 3million gallons of this toxic material
(Chief et al 2016). Much of the contaminated water and sludge
flowed into the Animas River, the upper reaches of which were
already adversely affected by decades of slow seepage of acidic
water from the mine. The Animas River flows into the San Juan
River and ultimately into the Colorado River (traversing 5 states -
Colorado, Utah, NewMexico, Arizona, Nevada, and California).
The sudden release of large volumes of toxic material, that
included lead and arsenic, had a widespread impact that
extended far downstream, disrupting the drinking water supply
of towns and halting recreational activities and irrigation of
crops leading to heavy crop failure. The impact of the acid
mine drainage on water quality and river bed sediments
appears to have been fairly short lived (the Animas River had
poor water quality pre-spill) as snow melt helped to dilute the
river water and wash away contaminated sediment (Cohen
2015). However, the spill had serious financial consequences
for many people, due to tourism and agricultural losses. As a
consequence, many states and individuals are suing the EPA for
damages (Roberts 2016).
CASE STUDY
Acid mine drainage in mountain areas – a slow motion
environmental problem
Retention ponds set up by the US EPA following the accidental release of acid mine water from the Gold King mine in Colorado in
2015. The water in the ponds is treated with lime which raises the pH and sodium hydroxide solution which facilitates sedimentation
of the metals prior to release of the water. The process is time consuming and expensive. As of August 2016, the US EPA had dedicated
$29 million to the clean-up and remediation effort (US EPA 2016).
Photo
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Wikimedia/EPA