ENVIRONMENTAL EFFECTS OF THE 1978 SUNNYSIDE MINE FLOOD

In 1978, the pillar of rock and sediment between glacial Lake Emma and the Sunnyside Mine collapsed, draining 5-25 M gallons of water and sediment through the mine and the American Tunnel within a few hours (Thompson, 2018). This caused a major flood in Cement Creek, a tributary of the Animas River north of Silverton, Colorado. While work has been done on the geochemistry of mine outwash in the same drainage from the 2015 Gold King Mine spill, the material from the Sunnyside Mine flood has not been extensively studied previously. This study aims to determine if the 1978 Sunnyside Mine flood had significant geochemical and geomorphic effects and continues to affect the environment today. Likely flood deposits were identified approximately fifteen centimeters above the typical spring flood level based on sediment characteristics, interviews with witnesses to the flood and community stakeholders, as well as newspaper articles and photographs from shortly after the flood. Cement Creek sediment samples from flood and non-flood deposits were analyzed with NIR spectroscopy for mineralogy. Sediment samples from the Sunnyside flood contained vermiculite, iron smectite, zeolites, gypsum, and secondary copper minerals, while most stream sediment included ferrihydrite, K-illite, and vermiculite. The significant difference in the minerals present, and the remaining flood horizon sediments indicate that the Sunnyside Mine flood impacted the Cement Creek watershed, including contributing a higher than normal level of heavy metals to the stream, which are known to have negative effects on wildlife, aquatic ecosystems, and human health (e.g., Simate & Ndlovu, 2014). Understanding the impact that a major disaster like the Sunnyside Mine flood had on the area is important to have a better picture of a region that continues to face environmental impacts from mining activities.

References:

Simate, G. S., & Ndlovu, S. (2014). Acid mine drainage: Challenges and opportunities. Journal of Environmental Chemical Engineering, 2(3), 1785-1803.

Thompson, J. P. (2018). River of lost souls: The science, politics, and greed behind the gold king mine disaster. Torrey House Press.