State And Federal Officials Determine Fish Kill In Left Hand Creek Is Related To Captain Jack Mine Site

The U.S. Environmental Protection Agency and the Colorado Department of Public Health and Environment have determined that a release of contaminated water originating from a mine tunnel at the Captain Jack Mill Superfund site likely was responsible for a fish kill reported Oct. 22 in the upper portions of Left Hand Creek.

Field monitoring and the results of water samples collected at various locations along Left Hand Creek indicate water discharging from the Big Five tunnel was more acidic and contained higher levels of heavy metals than in previous water samples. The high acidity and heavy metals, coupled with the seasonal low flows in Left Hand Creek, resulted in water quality impacts approximately five miles below the superfund site.

The Captain Jack Mill site was added to the Superfund national priorities list in 2003. The Colorado Department of Public Health and Environment and EPA have been working to mitigate the impacts of historic mining activities since the cleanup plan was issued in 2008. A portion of the remedy involves an in-tunnel treatment system to improve the quality of the water flowing out of the Big Five tunnel.

Following reports of the Oct. 22 fish kill, EPA and the state health department temporarily closed the flow-through valve on the Big Five tunnel bulkhead and are planning next steps. Over the next several days, the agencies will be monitoring the stream water quality while continuing to assess the in-tunnel treatment system performance and implementing changes to the system as necessary to improve water quality.

The Left Hand Water District tests both raw and treated water on a continuous basis. The intake remains open following test results that met water quality standards showing no impacts to downstream water users.