- YellowRiver.jpg (36.62 KiB) Viewed 2267 times
Today, the U.S. government, the State of Colorado and Sunnyside Gold Corp. agreed to a tentative agreement on how to share responsibility for the clean-up of the Gold King Mine disaster that dumped over 3 million gallons of acid mine water into Cement Creek and the Animas River in southwest Colorado. Acid mine water can reach pH values as low as 1.5 to 2, which is the pH of the sulfuric acid in lead car batteries. The acidity is created by the chemical weathering of sulfide minerals that produces sulfuric acid. The damage to the ecosystem is not only from the highly acidic water, but that acidity leaches heavy metals from the sulfide-bearing ore.
The putrid yellow color of the river is from ferric iron (Fe+3). At the point of release, the iron ions are ferrous (Fe+2). As the acid mine water travels downstream it is diluted raising the pH to the point that the iron is oxidized to ferric iron, which then precipitates out of solution (usually as the iron "rust" minerals goethite and hematite).
Here is an Associated Press story posted on Comcast.
US, Colorado reach proposed settlement in 2015 mine spill By JAMES ANDERSON, AP / 8:19 pm ET Fri Jan 21, 2022
ETA: I hope this triggers Pat Gund to drop by and add his take. We geologist should stick together.The proposed settlement announced Friday would direct $90 million to cleanup at the Bonita Peak Mining District Superfund site in southwest Colorado, according to the U.S. Environmental Protection Agency and Denver-based Sunnyside Gold Corp. The agreement must be approved by a federal judge after a 30-day public comment period.
Sunnyside, which owns property in the district, and the EPA have been in a long-running battle over the cleanup. The EPA has targeted Sunnyside to help pay for the cleanup, and the company has resisted, launching multiple challenges to the size and management of the project.
An EPA-led contractor crew was doing excavation work at the entrance to the Gold King Mine, another site in the district not owned by Sunnyside, in August 2015 when it inadvertently breached a debris pile that was holding back wastewater inside the mine.
An estimated 3 million gallons (11 million liters) of wastewater poured out, carrying nearly 540 U.S. tons (490 metric tons) of metals, mostly iron and aluminum. Rivers in Colorado, New Mexico, the Navajo Nation and Utah were polluted. Downstream water utilities shut down intake valves and farmers stopped drawing from the rivers.
