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Heavy metal sediment released into Uncompahgre River last week

Water quality impacts of hydropower reservoir flushing unknown

     Seeing the Uncompahgre River filled with a hazy, orange flow last week was rather disconcerting, coming less than two months after the toxic spill from the Gold King Mine in Silverton that turned the Animas River orange. At 9:40 a.m. last Thursday, the Ouray County Sheriff's Office sent out a text and email alert to notify people that the river's discoloration was caused by a planned dam release. 

     The Ouray Hydropower Plant flushed its reservoir to reduce sediment buildup, resulting in the release of higher-than-normal levels of heavy metals. These metals were deposited in the reservoir over time as they flowed downstream from natural processes and abandoned mines in the upper watershed. The plant itself does not contribute heavy metals to the water, but the flushing of the dam once or twice a year releases them.
     Last week’s river event does not impact the local water supply, as the river is not used as residential water by Ouray or Ridgway. While the fish and insect populations are already damaged by the consistently high heavy metal levels in the river, it is unclear how the increased concentrations during these flushing events affect the remaining aquatic life and recreational river users. 
     A study of river content after a flushing event in 2001 showed several heavy metals including arsenic, barium and copper were in much greater concentrations than usual, with lead levels increased by 30 times and iron by 40 times. No study has ever been conducted to determine the environmental impact of the higher concentrations of heavy metals, but most of the upper Uncompahgre south of the Ridgway Reservoir is on the Clean Water Act’s list of impaired waters due to high heavy metal loading in the headwaters.
     The Uncompahgre Watershed Partnership (UWP) is dedicated to monitoring river events like last week’s, sharing information with the community and developing action plans to address potential water quality impacts. However, there are no known feasible alternatives to the hydropower flushing, and the resulting orange flow is just a highly visible symptom of a much larger problem – the multitude of abandoned mines upstream that are contributing heavy metals to our waterways. The UWP is focusing its efforts on mine remediation and has recently completed its first two projects. Look for a more in-depth report on these topics in UWPs next e-newsletter coming to your inbox in early October. 

Special thanks to Agnieszka Przeszlowska, a river restoration consultant working with the Uncompahgre Watershed Partnership, for her contributions of information and photos in this E-Alert.

The Uncompahgre River flowed its usual greenish-brown color before the hydropower dam flushing on Sept. 24. 
The Uncompahgre River was noticeably orange on Sept. 24 after the hydropower dam flushed sediments from its reservoir. Based on data collected after a similar flushing in 2001, the water was full of extremely high concentrations of lead, iron, copper, arsenic and other heavy metals originating from abandoned mines and high country mineral deposits.

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